Search results

Title: Analysis methods for characterizing salinity variability from multivariate time series applied to the Apalachicola Bay estuary.
Creator: Morey, Steven, Dukhovskoy, Dmitry
Abstract/Description: Statistical analysis methods are developed to quantify the impacts of multiple forcing variables on the hydrographic variability within an estuary instrumented with an enduring observational system. The methods are applied to characterize the salinity variability within Apalachicola Bay, a shallow multiple-inlet estuary along the northeastern Gulf of Mexico coast. Thirteen-year multivariate time series collected by the National Estuary Research Reserve at three locations within the bay are...
Show moreStatistical analysis methods are developed to quantify the impacts of multiple forcing variables on the hydrographic variability within an estuary instrumented with an enduring observational system. The methods are applied to characterize the salinity variability within Apalachicola Bay, a shallow multiple-inlet estuary along the northeastern Gulf of Mexico coast. Thirteen-year multivariate time series collected by the National Estuary Research Reserve at three locations within the bay are analyzed to determine how the estuary responds to variations in external forcing mechanisms, such as freshwater discharge, precipitation, tides and local winds, at multiple time scales. The analysis methods are used to characterize the estuarine variability under differing flow regimes of the Apalachicola River, a managed waterway, with particular focus on extreme events and scales of variability that are critical to local ecosystems. Multivariate statistical models are applied that describe the salinity response to winds from multiple directions, river flow, and precipitation at daily, weekly, and monthly time scales to understand the response of the estuary under different climate regimes. Results show that the salinity is particularly sensitive to river discharge and wind magnitude and direction, with local precipitation being largely unimportant. Applying statistical analyses with conditional sampling quantifies how the likelihoods of high salinity and long duration high salinity events, conditions of critical importance to estuarine organisms, change given the state of the river flow. Intraday salinity range is shown to be negatively correlated with the salinity, and correlated with river discharge rate.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0047, 10.1175/JTECH-D-11-00136.1
Format: Citation

Title: Evaluation of dynamically downscaled reanalysis precipitation data for hydrological application in the southeast United States.
Creator: Bastola, Satish, Misra, Vasubandhu
Abstract/Description: Skillful and reliable precipitation data is essential for seasonal hydrologic forecasting, and generation of hydrological data. Though output from dynamic downscaling methods is used for hydrological application, the existence of systematic errors in dynamically downscaled data adversely affects the skill of hydrologic forecasting. This study evaluates the precipitation data derived by dynamically downscaling the global atmospheric reanalysis data by propagating them through three...
Show moreSkillful and reliable precipitation data is essential for seasonal hydrologic forecasting, and generation of hydrological data. Though output from dynamic downscaling methods is used for hydrological application, the existence of systematic errors in dynamically downscaled data adversely affects the skill of hydrologic forecasting. This study evaluates the precipitation data derived by dynamically downscaling the global atmospheric reanalysis data by propagating them through three hydrological models. Hydrological models are calibrated for 28 basins located in the southeast United States (U.S.) that is minimally affected by human intervention. Calibrated hydrological models are forced with five different types of datasets: global (NCEP R2 and ERA40) at their native resolution; dynamically downscaled; synthetically generated; bias-corrected, dynamically downscaled and bias-corrected global reanalysis. Our study indicates that over the 28 watersheds in the southeast U.S., the simulated hydrological response to the biascorrected dynamically downscaled data is superior. In comparison to synthetically generated meteorological forcing, the dynamically downscaled data result in more realistic hydrological simulations. Therefore, we conclude that dynamical downscaling, although resource intensive, is better suited for hydrological simulation in the southeast U.S.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0057
Format: Citation

Title: Generation of an empirical soil moisture initialization and its potential impact on subseasonal forecasting skill of continental precipitation and air temperature.
Creator: Boisserie, Marie
Abstract/Description: The effect of the PAR technique on the model soil moisture estimates is evaluated using the Global Soil Wetness Project Phase 2 (GSWP-2) multimodel analysis product (used as a proxy for global soil moisture observations) and actual in-situ observations from the state of Illinois. The results show that overall the PAR technique is effective; across most of the globe, the seasonal and anomaly variability of the model soil moisture estimates well reproduce the values of GSWP-2 in the top 1.5 m...
Show moreThe effect of the PAR technique on the model soil moisture estimates is evaluated using the Global Soil Wetness Project Phase 2 (GSWP-2) multimodel analysis product (used as a proxy for global soil moisture observations) and actual in-situ observations from the state of Illinois. The results show that overall the PAR technique is effective; across most of the globe, the seasonal and anomaly variability of the model soil moisture estimates well reproduce the values of GSWP-2 in the top 1.5 m soil layer; by comparing to in-situ observations in Illinois, we find that the seasonal and anomaly soil moisture variability is also well represented deep into the soil. Therefore, in this study, we produce a new global soil moisture analysis dataset that can be used for many land surface studies (crop modeling, water resource management, soil erosion, etc.). Then, the contribution of the resulting soil moisture analysis (used as initial conditions) on air temperature and precipitation forecasts are investigated. For this, we follow the experimental set up of a model intercomparison study over the time period 1986-1995, the Global Land-Atmosphere Coupling Experiment second phase (GLACE-2), in which the FSU/COAPS climate model has participated. The results of the summertime air temperature forecasts show a significant increase in skill across most of the U.S. at short-term to subseasonal time scales. No increase in summertime precipitation forecasting skill is found at short-term to subseasonal time scales between 1986 and 1995, except for the anomalous drought year of 1988. We also analyze the forecasts of two extreme hydrological events, the 1988 U.S. Drought and the 1993 U.S. flood. In general, the comparison of these two extreme hydrological event forecasts shows greater improvement for the summertime of 1988 than that of 1993, suggesting that soil moisture contributes more to the development of a drought than a flood. This result is consistent with Dirmeyer and Brubaker [1999] and Weaver et al. [2009]. By analyzing the evaporative sources of these two extreme events using the back-trajectory methodology of Dirmeyer and Brubaker [1999], we find similar results as this latter paper; the soil moisture-precipitation feedback mechanism seems to play a greater role during the drought year of 1988 than the flood year of 1993. Finally, the accuracy of this soil moisture initialization depends upon the quality of the precipitation dataset that is assimilated. Because of the lack of observed precipitation at a high temporal resolution (3-hourly) for the study period (1986-1995), a reanalysis product is used for precipitation assimilation in this study. It is important to keep in mind that precipitation data in reanalysis sometimes differ significantly from observations since precipitation is often not assimilated into the reanalysis model. In order to investigate that aspect, a similar analysis to that we performed in this study could be done using the 3-hourly Tropical Rainfall Measuring Mission (TRMM) dataset available for a the time period 1998-present. Then, since the TRMM dataset is a fully observational dataset, we expect the soil moisture initialization to be improved over that obtained in this study, which, in turn, may further increase the forecast skill.
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Date Issued: 2010
Identifier: FSU_migr_coaps_pubs-0002, fsu:209864
Format: Citation

Title: Generation of mesoscale eddies in the lee of the Hawaiian Islands.
Creator: Jia, Yinglai, Calil, P., Chassignet, E., Metzger, E., Potemra, J., Richards, K., Wallcraft, Alan J.
Abstract/Description: The ocean west of the main Hawaiian Islands is characterized by enhanced eddy kinetic energy arising from the abundance of locally generated mesoscale eddies, most frequently in the area west of the island of Hawaii. Two mechanisms of eddy generation in the wake of an island are examined with numerical model experiments. The first, eddy generation and shedding by an oceanic flow around an oceanic barrier, requires the existence of strong westward flows to the north and south of the island of...
Show moreThe ocean west of the main Hawaiian Islands is characterized by enhanced eddy kinetic energy arising from the abundance of locally generated mesoscale eddies, most frequently in the area west of the island of Hawaii. Two mechanisms of eddy generation in the wake of an island are examined with numerical model experiments. The first, eddy generation and shedding by an oceanic flow around an oceanic barrier, requires the existence of strong westward flows to the north and south of the island of Hawaii. Model solutions show such westward flows and generation of eddies by these flows although the intensity of the eddies and the generation frequency are much lower than that derived from altimetry. As a result, these eddies contribute an insignificant amount of eddy kinetic energy in the region. The second, eddy generation and shedding by an atmospheric flow around an atmospheric barrier, is based on oceanic upwelling and downwelling induced by surface wind shear, effectively introducing sinks and sources to the ocean interior. Previous idealized modeling studies have shown that oceanic eddies can be generated by sufficiently strong forcing (source or sink), providing an explanation why eddy occurrences in the lee of the island of Hawaii coincide with periods of strong trade winds. Eddy generation characteristics in the model experiments are consistent with this mechanism in terms of time of occurrence, strength and the resulting eddy kinetic energy. Major discrepancies are in eddy propagation and therefore eddy distribution in the regional domain due to the complex nature of eddy-eddy interactions.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0051, 10.1029/2011JC007305
Format: Citation

Title: Evolution of Land Surface Air Temperature Trend.
Creator: Ji, Fei, Wu, Zhaohua, Huang, Jianping, Chassignet, E.
Abstract/Description: The global climate has been experiencing significant warming at an unprecedented pace in the past century1, 2. This warming is spatially and temporally non-uniform, and one needs to understand its evolution in order to better evaluate its potential societal and economic impact. In this paper, the evolution of global land surface temperature trend in the last century is diagnosed using the spatial–temporally multidimensional ensemble empirical mode decomposition method3. We find that the...
Show moreThe global climate has been experiencing significant warming at an unprecedented pace in the past century1, 2. This warming is spatially and temporally non-uniform, and one needs to understand its evolution in order to better evaluate its potential societal and economic impact. In this paper, the evolution of global land surface temperature trend in the last century is diagnosed using the spatial–temporally multidimensional ensemble empirical mode decomposition method3. We find that the noticeable warming (>0.5 K) started sporadically over the global land and accelerated until around 1980. Both the warming rate and spatial structure have changed little since. The fastest warming in recent decades (>0.4 K/decade) occurred in northern midlatitudes. From a zonal average perspective, noticeable warming (>0.2 K since 1900) first took place in the subtropical and subpolar regions of the Northern Hemisphere, followed by subtropical warming in the Southern Hemisphere. The two bands of warming in the Northern Hemisphere expanded from 1950 to 1985 and merged to cover the entire Northern Hemisphere.
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Date Issued: 2014
Identifier: FSU_migr_coaps_pubs-0064, 10.1038/nclimate2223
Format: Set of related objects

Title: High-latitude ocean and sea ice surface fluxes: requirements and challenges for climate research.
Creator: Bourassa, Mark, Gille, Sarah Tragler, Bitz, Cecilia M., Carlson, David, Cerovecki, Ivana, Cronin, Meghan, Drennan, Will, Fairall, Chris, Hoffman, Ross, Magusdottir, Gudrun,...
Show moreBourassa, Mark, Gille, Sarah Tragler, Bitz, Cecilia M., Carlson, David, Cerovecki, Ivana, Cronin, Meghan, Drennan, Will, Fairall, Chris, Hoffman, Ross, Magusdottir, Gudrun, Pinker, Rachel, Renfrew, Ian, Serreze, Mark C., Speer, Kevin G. (Kevin George), Talley, Lynne D., Wick, Gary
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Abstract/Description: Improving knowledge of air-sea exchanges of heat, momentum, fresh water, and gases is critical to understanding climate, and this is particularly true in high-latitude regions, where anthropogenic climate change is predicted to be exceptionally rapid. However, observations of these fluxes are extremely scarce in the Arctic, the Southern Ocean, and the Antarctic marginal seas. High winds, high sea state, extreme cold temperatures, seasonal sea ice, and the remoteness of the regions all...
Show moreImproving knowledge of air-sea exchanges of heat, momentum, fresh water, and gases is critical to understanding climate, and this is particularly true in high-latitude regions, where anthropogenic climate change is predicted to be exceptionally rapid. However, observations of these fluxes are extremely scarce in the Arctic, the Southern Ocean, and the Antarctic marginal seas. High winds, high sea state, extreme cold temperatures, seasonal sea ice, and the remoteness of the regions all conspire to make observations difficult to obtain. Annually averaged heat-flux climatologies can differ by more than their means, and in many cases there is no clear consensus about which flux products are most reliable. Although specific flux accuracy requirements for climate research vary depending on the application, in general fluxes would better represent high-latitude processes if wind stresses achieved 0.01Nm-2 accuracy at high wind speed and if heat fluxes achieved 10 W m-2 accuracy (averaged over several days) with 25 km grid spacing. Improvements in flux estimates will require a combination of efforts, including a concerted plan to make better use of ships of opportunity to collect meteorological data, targeted efforts to deploy a few flux moorings in high-wind regions, and improved satellite retrievals of flux-related variables.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0017
Format: Citation

Title: High-resolution satellite surface latent heat fluxes in North Atlantic hurricanes.
Creator: Liu, Jiping, Curry, Judith A., Clayson, Carol Anne, Bourassa, Mark
Abstract/Description: This study presents a new high-resolution satellite-derived ocean surface flux product, XSeaFlux, which is evaluated for its potential use in hurricane studies. The XSeaFlux employs new satellite data sets using improved retrieval methods, and uses a new bulk flux algorithm formulated for high wind conditions. The XSeaFlux latent heat flux (LHF) performs much better than the existing numerical weather prediction reanalysis and satellite-derived flux products in a comparison with measurements...
Show moreThis study presents a new high-resolution satellite-derived ocean surface flux product, XSeaFlux, which is evaluated for its potential use in hurricane studies. The XSeaFlux employs new satellite data sets using improved retrieval methods, and uses a new bulk flux algorithm formulated for high wind conditions. The XSeaFlux latent heat flux (LHF) performs much better than the existing numerical weather prediction reanalysis and satellite-derived flux products in a comparison with measurements from the Coupled Boundary Layer Air-Sea Transfer (CBLAST) field experiment. Also, the XSeaFlux shows well-organized LHF structure and large LHF values in response to hurricane conditions relative to the other flux products. The XSeaFlux data set is used to interpret details of the ocean surface LHF for selected North Atlantic hurricanes. Analysis of the XSeaFlux data set suggests that ocean waves, sea spray, and cold wake have substantial impacts on LHF associated with the hurricanes.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0023, 10.1175/2011MWR3548.1
Format: Citation

Title: California reanalysis downscaling at 10 km using an ocean-atmosphere coupled regional model system.
Creator: Li, Haiqin, Kanamitsu, Masao, Hong, Song-You
Abstract/Description: A fully coupled regional downscaling system for both the Regional Spectral Model (RSM) for atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean was developed for the purpose of downscaling observed analysis or global model outputs. The two models share the same grid and resolution with efficient parallelization through the use of dual message passing interfaces. Coupled downscaling was performed using historical Simple Ocean Data Assimilation (SODA) oceanic reanalysis and...
Show moreA fully coupled regional downscaling system for both the Regional Spectral Model (RSM) for atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean was developed for the purpose of downscaling observed analysis or global model outputs. The two models share the same grid and resolution with efficient parallelization through the use of dual message passing interfaces. Coupled downscaling was performed using historical Simple Ocean Data Assimilation (SODA) oceanic reanalysis and NCEP/DOE (R-2) atmospheric reanalysis in order to study the impact of coupling on the regional scale atmospheric analysis. The results were subsequently compared with the uncoupled downscaling forced by the prescribed observed sea surface temperature (SST). An evaluation of the SST and ocean current from the coupled experiment yielded realistic small-scale oceanic features that are nearly absent in the oceanic reanalysis. Upwelling over the California coast is well resolved and comparable to findings obtained from high-resolution observations. The coupling impact on the atmospheric circulation mainly modulates the near surface atmospheric variables when compared to the simulation conducted without coupling. The duration of the Catalina Eddy detected in the coupled experiment increased by about 6.5% when compared to that in the uncoupled experiment. The offshore land breeze is enhanced by about 10%, whereas the change in the onshore sea breeze is very small during the summer.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0059, 10.1029/2011JD017372
Format: Citation

Title: Climate Data Issues from an Oceanographic Remote Sensing Perspective.
Creator: Katsaros, Kristina, Bentamy, Abderrahim, Bourassa, Mark, Ebuchi, Naoto, Gower, James, Liu, W., Vignudelli, Stefano
Abstract/Description: In this chapter we review several climatologically important variables with a history of observation from spaceborne platforms. These include sea surface temperature and wind vectors, altimetric estimates of sea surface height, energy and water vapor fluxes at the sea surface, precipitation over the ocean, and ocean color. We then discuss possible improvements in sampling for climate and climate change definition. Issues of consistency of different data sources, archiving and distribution of...
Show moreIn this chapter we review several climatologically important variables with a history of observation from spaceborne platforms. These include sea surface temperature and wind vectors, altimetric estimates of sea surface height, energy and water vapor fluxes at the sea surface, precipitation over the ocean, and ocean color. We then discuss possible improvements in sampling for climate and climate change definition. Issues of consistency of different data sources, archiving and distribution of these types of data are discussed. The practical prospect of immediate international coordination through the concept of virtual constellations is discussed and applauded.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0062, 10.1007/978-3-642-16541-2_2
Format: Citation

Title: On the variability of the Mediterranean Outflow Water in the Atlantic Ocean from 1948 to 2006.
Creator: Bozec, Alexandra, Lozier, M., Chassignet, E., Halliwell, George
Abstract/Description: Recent work has shown that variability in the properties and/or transport of Mediterranean Seawaters spilling across the Strait of Gibraltar into the North Atlantic have had little impact on the variability of Mediterranean Outflow Water (MOW) in the that basin over the past fifty years. Here we investigate whether circulation changes are the dominant source of MOW variability in the North Atlantic between 1948 and 2006. Using a 1/3° North Atlantic configuration of the HYbrid Coordinate Ocean...
Show moreRecent work has shown that variability in the properties and/or transport of Mediterranean Seawaters spilling across the Strait of Gibraltar into the North Atlantic have had little impact on the variability of Mediterranean Outflow Water (MOW) in the that basin over the past fifty years. Here we investigate whether circulation changes are the dominant source of MOW variability in the North Atlantic between 1948 and 2006. Using a 1/3° North Atlantic configuration of the HYbrid Coordinate Ocean Model combined with the Marginal Sea Boundary Condition model, two simulations forced by either climatological or interannual atmospheric fields are performed. The interannual simulation reproduces the observed MOW variability without Mediterranean Seawater changes. Thus, we conclude that MOW variability in the last 60 years is a consequence of circulation changes in the North Atlantic. A series of simulations that separate the mechanical effect of the wind from the impact of buoyancy forcing show that MOW variability can be attributed to shifts between its dominant northward and westward pathways. The pathway shifts from predominantly northward between 1950 and 1975 to predominantly westward between 1975 and 1995 and finally back to northward after 1995. Though these pathway shifts appear to be wind-induced, the property changes are caused by the combined impact of wind and buoyancy forcing on the circulation of the North Atlantic.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0015, 10.1029/2011JC007191
Format: Citation

Title: Operational marine forecasters and the importance of marine forecasting.
Creator: Sullivan, D., Murphree, Tom, Rosenfield, L., Smith, S.
Abstract/Description: A major goal of the Marine Advanced Technology Education (MATE) Center is to align curriculum and program development with the needs of employers. The Center believes that graduates from MATE-affiliated educational institutions should be well informed about workforce needs and well equipped with the skills required to enter marine technical occupations. To accomplish this, one of the methods used by the MATE Center is the development and use of Knowledge and Skill Guidelines. (Knowledge and...
Show moreA major goal of the Marine Advanced Technology Education (MATE) Center is to align curriculum and program development with the needs of employers. The Center believes that graduates from MATE-affiliated educational institutions should be well informed about workforce needs and well equipped with the skills required to enter marine technical occupations. To accomplish this, one of the methods used by the MATE Center is the development and use of Knowledge and Skill Guidelines. (Knowledge and Skill Guidelines may also be referred to as Occupational Guidelines or Standards or Skill Standards.) This document represents one such resource for Operational Marine Forecasters.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0013
Format: Citation

Title: A proxy for high-resolution regional reanalysis for the Southeast United States: assessment of precipitation variability in dynamically downscaled reanalyses.
Creator: Stefanova, Lydia, Misra, Vasubandhu, Chan, Steven, Griffin, Melissa, O'Brien, James J., Smith, III, Thomas
Abstract/Description: A variety of practical applications, such as hydrological and ecological modeling, require high-resolution meteorological data sets. A crucial, yet notoriously difficult to model, component of such data sets is precipitation. Here, we present an analysis of the seasonal, subseasonal, and diurnal variability of rainfall from the COAPS Land-Atmosphere Regional Reanalysis for the Southeast at 10-km resolution (CLARReS10). Most of our analysis focuses on the representation of summertime...
Show moreA variety of practical applications, such as hydrological and ecological modeling, require high-resolution meteorological data sets. A crucial, yet notoriously difficult to model, component of such data sets is precipitation. Here, we present an analysis of the seasonal, subseasonal, and diurnal variability of rainfall from the COAPS Land-Atmosphere Regional Reanalysis for the Southeast at 10-km resolution (CLARReS10). Most of our analysis focuses on the representation of summertime subseasonal and diurnal variability. Summer precipitation in the Southeast is a particularly challenging modeling problem because of the variety of regional-scale phenomena, such as sea breeze, thunderstorms and squall lines, tropical storms, and hurricanes, which are barely resolved in coarse atmospheric reanalyses, but which contribute significantly to the hydrological budget over the region. The National Centers for Environmental Prediction (NCEP) - Department of Energy (DOE) Reanalysis II (R2) and the European Centre for Medium-Range Weather Forecast (ECMWF) 40-year Reanalysis (ERA40) have been dynamically downscaled with the NCEP/Experimental Climate Prediction Center (ECPC) Regional Spectral Model (RSM). The downscaling has been performed over the Southeast United States at a horizontal resolution of 10 km for the period 1979-2001. The resulting regional reanalyses are compared to gridded observations and station data. We find that the downscaled reanalyses show good agreement with observations in terms of both the relative seasonal distribution and the diurnal structure of precipitation. The spatial distribution of precipitation has a wet bias over most of the region. There are noticeable differences between the two simulations: CLARReS10-ERA40 (the downscaled ERA40) tends to be wetter than CLARReS10-R2 (the downscaled R2), and the diurnal precipitation maximum occurs earlier in the day in CLARReS10- ERA40
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0027, 10.1007/s00382-011-1230-y
Format: Citation

Title: A vortex isolation and removal algorithm for numerical weather prediction model tropical cyclone applications.
Creator: Winterbottom, Henry R., Chassignet, E.
Abstract/Description: Inserting an externally defined (i.e., synthetic) tropical cyclone (TC) vortex into numerical weather prediction (NWP) model analyses requires that an existing TC vortex first be removed. Similarly, statistical-dynamical forecasting methods require that the larger-scale environmental attributes of the flow be separated (and preserved) from those on the smaller meso- and TC vortex scales. The existing operational methods to accomplish such tasks are optimized particularly for the respective...
Show moreInserting an externally defined (i.e., synthetic) tropical cyclone (TC) vortex into numerical weather prediction (NWP) model analyses requires that an existing TC vortex first be removed. Similarly, statistical-dynamical forecasting methods require that the larger-scale environmental attributes of the flow be separated (and preserved) from those on the smaller meso- and TC vortex scales. The existing operational methods to accomplish such tasks are optimized particularly for the respective models grid spacing resolution and thus are not general when applied to finer resolution analyses. Further, the existing methods often adhere to rigid assumptions regarding the size and structure of the TC. A methodology is provided in this study to overcome these limitations. This is accomplished through analyzing the features of the NWP model analysis (e.g., the variables in the vicinity of the TC) and then systematically removing the TC through the application of both a smoothing operator and a subsequent statistical evaluation of the smoothed analysis variable. The value of our methodology is determined when analyzing the results from experiments initialized from an analysis containing TCs and those initialized from analyses without the respective TCs. This methodology is also robust for it does not require a tuning of parameters relative to varying grid-spacing resolutions and may thus benefit the statistical-dynamical TC intensity prediction schemes.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0050, 10.1029/2011MS000088
Format: Citation

Title: Understanding wet season variations over Florida.
Creator: Misra, Vasubandhu, DiNapoli, Steven
Abstract/Description: The wet season of Florida is well defined and is invariably centered in the boreal summer season of June–July–August. In this observational study we objectively define the Length of the Wet Season (LOWS) for Florida and examine its variations with respect to El Niño and the Southern Oscillation (ENSO) and the Atlantic Warm Pool (AWP). Our study reveals that ENSO variability has a profound influence on the LOWS especially over south Florida and parts of panhandle Florida prior to 1976. In the...
Show moreThe wet season of Florida is well defined and is invariably centered in the boreal summer season of June–July–August. In this observational study we objectively define the Length of the Wet Season (LOWS) for Florida and examine its variations with respect to El Niño and the Southern Oscillation (ENSO) and the Atlantic Warm Pool (AWP). Our study reveals that ENSO variability has a profound influence on the LOWS especially over south Florida and parts of panhandle Florida prior to 1976. In the post-1976 era the influence of ENSO has significantly diminished. Our results show that in this pre-1976 era, warm (cold) ENSO events in the boreal winter are followed by long (short) LOWS over the region. This variation is consistent with warm (cold) ENSO events influencing early (late) onset of the wet season in the region. There is significant relationship of the LOWS in south and northeast Florida with the variation of the AWP. Unlike the teleconnection with ENSO the relationship of the demise of the wet season with AWP is stronger in the post-1976 period compared to the pre-1976 period. Furthermore the variability of the LOWS has increased in the post-1976 period.
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Date Issued: 2012
Identifier: FSU_migr_coaps_pubs-0056, 10.1007/s00382-012-1382-4
Format: Citation

Title: A comparison of sequential assimilation schemes for ocean prediction with the HYbrid Coordinate Ocean Model (HYCOM). Part I: Twin experiments.
Creator: Srinivasan, A.
Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0022
Format: Citation

Title: Top-down, bottom-up and physical controls on diatom-diazotroph assemblage growth in the Amazon River plume.
Creator: Stukel, Michael, Coles, Victoria, Brooks, Maureen, Hood, Raleigh
Abstract/Description: The nutrient-rich waters of the Amazon River plume (ARP) support dense blooms of diatom-diazotroph assemblages (DDAs) that introduce large quantities of new nitrogen to the planktonic ecosystem and, unlike other nitrogen-fixers, are likely to directly fuel vertical carbon flux. To investigate the factors controlling DDA blooms, we develop a five phytoplankton (cyanobacteria, diatoms, unicellular microbial diazotrophs, DDAs, and Trichodesmium), two zooplankton model and embed it within a 1/6°...
Show moreThe nutrient-rich waters of the Amazon River plume (ARP) support dense blooms of diatom-diazotroph assemblages (DDAs) that introduce large quantities of new nitrogen to the planktonic ecosystem and, unlike other nitrogen-fixers, are likely to directly fuel vertical carbon flux. To investigate the factors controlling DDA blooms, we develop a five phytoplankton (cyanobacteria, diatoms, unicellular microbial diazotrophs, DDAs, and Trichodesmium), two zooplankton model and embed it within a 1/6° resolution physical model of the tropical and subtropical Atlantic. The model generates realistic DDA blooms in the ARP and also exhibits basin-wide primary production, nitrogen fixation, and grazing rates consistent with observed values. By following ARP water parcels with synthetic Lagrangian drifters released at the river mouth we are able to assess the relative impacts of grazing, nutrient supply, and physical forcing on DDA bloom formation. DDA bloom formation is stimulated in the nitrogen-poor and silica-rich water of the ARP by decreases in grazing pressure when mesozooplankton (which co-occur in high densities with coastal diatom blooms) concentrations decrease. Bloom termination is driven primarily by silica limitation of the DDAs. In agreement with in situ data, this net growth niche for DDAs exists in a salinity range from ∼20–34 PSU, although this co-occurrence is coincidental rather than causative. Because net growth rates are relatively modest, bloom formation in ARP water parcels depends critically on the time spent in this ideal habitat, with high DDA biomass only occurring when water parcels spent >23 days in the optimal habitat niche.
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Date Issued: 2014
Identifier: FSU_migr_eoas_faculty_publications-0001, 10.5194/bg-11-3259-2014
Format: Citation

Title: The arrested Agulhas retroflection.
Creator: Nof, Doron, Zharkov, Volodymyr, Ortiz, Joseph, Paldor, Nathan, Arruda, Wilton, Chassignet, E.
Abstract/Description: Paleoceanographic proxy data indicate that the Agulhas leakage into the South Atlantic was dramatically reduced during glacial times. In our former papers, we suggested that this was due to a northward shift of the zero wind stress curl that, in turn, forced the retroflection to occur farther north, where the slant of the coastline relative to the north is steep. In the present paper, we propose that strong westerlies (0.4 Pa, implying a wind speed of ~ 12 m s-1 at zero degrees centigrade),...
Show morePaleoceanographic proxy data indicate that the Agulhas leakage into the South Atlantic was dramatically reduced during glacial times. In our former papers, we suggested that this was due to a northward shift of the zero wind stress curl that, in turn, forced the retroflection to occur farther north, where the slant of the coastline relative to the north is steep. In the present paper, we propose that strong westerlies (0.4 Pa, implying a wind speed of ~ 12 m s-1 at zero degrees centigrade), which were supposedly common during glaciations, can also arrest the leakage. This arrest occurred because the wind stress opposed the momentum flux associated with the retroflection; such an arrest did not require the retroflection to shift in latitude. We use a simple, nonlinear, "reduced gravity" model to show analytically and numerically that, under the above conditions, the eastward wind stress compensates for the zonal westward flow-force associated with the retroflection, thus avoiding the development and shedding of rings. For a nearly zonal wall, westerly winds, and small upper layer thickness along the wall, the arresting wind stress is found, theoretically, to be, τx~0.042α3/2ρf[(2fQ)3/g']1/4 where α is twice the retroflection eddy vorticity, ρ the water density, and Q the Agulhas Current volume flux; the remaining notation is conventional.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0053, 10.1357/002224011799849453
Format: Citation

Title: A latent heat retrieval and its effects on the intensity and structure change of Hurricane Guillermo (1997). Part I: the algorithm and observations.
Creator: Guimond, S., Bourassa, Mark, Reasor, Paul
Abstract/Description: Despite the fact that latent heating in cloud systems drives many atmospheric circulations, including tropical cyclones, little is known of its magnitude and structure, largely because of inadequate observations. In this work, a reasonably high-resolution (2 km), four-dimensional airborne Doppler radar retrieval of the latent heat of condensation/evaporation is presented for rapidly intensifying Hurricane Guillermo (1997). Several advancements in the basic retrieval algorithm are shown,...
Show moreDespite the fact that latent heating in cloud systems drives many atmospheric circulations, including tropical cyclones, little is known of its magnitude and structure, largely because of inadequate observations. In this work, a reasonably high-resolution (2 km), four-dimensional airborne Doppler radar retrieval of the latent heat of condensation/evaporation is presented for rapidly intensifying Hurricane Guillermo (1997). Several advancements in the basic retrieval algorithm are shown, including 1) analyzing the scheme within the dynamically consistent framework of a numerical model, 2) identifying algorithm sensitivities through the use of ancillary data sources, and 3) developing a precipitation budget storage term parameterization. The determination of the saturation state is shown to be an important part of the algorithm for updrafts of -5 m s -1 or less. The uncertainties in the magnitude of the retrieved heating are dominated by errors in the vertical velocity. Using a combination of error propagation and Monte Carlo uncertainty techniques, biases are found to be small, and randomly distributed errors in the heating magnitude are ~16% for updrafts greater than 5 m s -1 and ~156% for updrafts of 1 m s -1. Even though errors in the vertical velocity can lead to large uncertainties in the latent heating field for small updrafts/downdrafts, in an integrated sense the errors are not as drastic. In Part II, the impact of the retrievals is assessed by inserting the heating into realistic numerical simulations at 2-km resolution and comparing the generated wind structure to the Doppler radar observations of Guillermo.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0018, 10.1175/2011JAS3700.1
Format: Citation

Title: A modeling study of the interaction between the Atlantic Warm Pool, the tropical Atlantic easterlies, and the Lesser Antilles.
Creator: Chan, Steven, Misra, Vasubandhu, Smith, H.
Abstract/Description: The European Centre for Medium-Range Forecasts Reanalysis-40 and National Centers for Environmental Prediction (NCEP)/Department of Energy reanalyses are downscaled over the eastern Caribbean and Lesser Antilles using the NCEP-Scripps Regional Spectral Model for Augusts when the Atlantic Warm Pool (AWP) area is the most anomalous. The simulations show a two-way influence between the Lesser Antilles and the AWP: the islands modulate the regional atmospheric circulation, and AWP variations...
Show moreThe European Centre for Medium-Range Forecasts Reanalysis-40 and National Centers for Environmental Prediction (NCEP)/Department of Energy reanalyses are downscaled over the eastern Caribbean and Lesser Antilles using the NCEP-Scripps Regional Spectral Model for Augusts when the Atlantic Warm Pool (AWP) area is the most anomalous. The simulations show a two-way influence between the Lesser Antilles and the AWP: the islands modulate the regional atmospheric circulation, and AWP variations modulate the interannual variabilities of the islands. The Lesser Antilles introduce diurnal variations and drag to the easterlies. The presence of the islands modulates the prevalent easterlies as a result of the daytime heating of the islands and the consequent boundary layer expansion. The modulations are sensitive to the islands' size and topography. Small and flat islands act as thermal plumes, but the modulations of large and hilly islands are during the daytime as their boundary layer expands. The manifestation of the atmospheric response to the sea surface temperature (SST) anomalies over the islands is sensitive to the island orography. For most islands, the atmospheric response to the SST anomalies is reflected only during the daytime. For all 1-grid-point islands and Antigua, nighttime and dawn minimum temperatures are modulated to the same degree as the daytime maximum. For island rainfall, downscaling reduces the gross overestimations of rainfall in the reanalyses. However, our downscaling results suggest that there is room for improvement in simulating the marine surface diurnal cycle.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0029, 10.1029/2010JD015260
Format: Citation

Title: The influence of the Atlantic Warm Pool on Panhandle Florida Sea Breeze.
Creator: Misra, Vasubandhu, Moeller, Lauren, Stefanova, Lydia, Chan, Steven, O'Brien, James J., Smith, III, Thomas, Plant, Nathaniel
Abstract/Description: In this paper we examine the variations of the boreal summer season sea breeze circulation along the Florida panhandle coast from relatively high resolution (10 km) regional climate model integrations. The 23 year climatology (1979-2001) of the multidecadal dynamically downscaled simulations forced by the National Centers for Environmental Prediction-Department of Energy (NCEP-DOE) Reanalysis II at the lateral boundaries verify quite well with the observed climatology. The variations at...
Show moreIn this paper we examine the variations of the boreal summer season sea breeze circulation along the Florida panhandle coast from relatively high resolution (10 km) regional climate model integrations. The 23 year climatology (1979-2001) of the multidecadal dynamically downscaled simulations forced by the National Centers for Environmental Prediction-Department of Energy (NCEP-DOE) Reanalysis II at the lateral boundaries verify quite well with the observed climatology. The variations at diurnal and interannual time scales are also well simulated with respect to the observations. We show from composite analyses made from these downscaled simulations that sea breezes in northwestern Florida are associated with changes in the size of the Atlantic Warm Pool (AWP) on interannual time scales. In large AWP years when the North Atlantic Subtropical High becomes weaker and moves further eastward relative to the small AWP years, a large part of the southeast U.S. including Florida comes under the influence of relatively strong anomalous low-level northerly flow and large-scale subsidence consistent with the theory of the Sverdrup balance. This tends to suppress the diurnal convection over the Florida panhandle coast in large AWP years. This study is also an illustration of the benefit of dynamic downscaling in understanding the low-frequency variations of the sea breeze.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0032, 10.1029/2010JD015367
Format: Citation

Title: Dynamic downscaling of the North American Monsoon with the NCEP-Scripps Regional Spectral Model from the NCEP CFS global model.
Creator: Chan, Steven, Misra, Vasubandhu
Abstract/Description: The June-September (JJAS) 2000-2007 NCEP coupled Climate Forecasting System (CFS) global hindcasts are downscaled over the North and South American continents with the NCEP-Scripps Regional Spectral Model (RSM) with anomaly nesting (AN) and without bias correction (control). A diagnosis of the North American Monsoon (NAM) in CFS and RSM hindcasts is presented here. RSM reduces errors caused by coarse resolution, but is unable to address larger scale CFS errors even with bias correction. CFS...
Show moreThe June-September (JJAS) 2000-2007 NCEP coupled Climate Forecasting System (CFS) global hindcasts are downscaled over the North and South American continents with the NCEP-Scripps Regional Spectral Model (RSM) with anomaly nesting (AN) and without bias correction (control). A diagnosis of the North American Monsoon (NAM) in CFS and RSM hindcasts is presented here. RSM reduces errors caused by coarse resolution, but is unable to address larger scale CFS errors even with bias correction. CFS has relatively weak Great Plains and Gulf of California low-level jets. Low-level jets are strengthened from downscaling, especially after AN bias correction. The RSM NAM hydroclimate shares similar flaws with CFS with problematic diurnal and seasonal variability. Flaws in both diurnal and monthly variability are forced by erroneous convection-forced divergence outside the monsoon core region in eastern and southern Mexico. NCEP Reanalysis shows significant seasonal variability errors, and AN shows little improvement in regional scale flow errors. Our results suggest extreme caution must be taken when the correction is applied relative to reanalyses. Analysis also shows North American Regional Reanalysis NAM seasonal variability has benefited from precipitation data assimilation, but many questions remain concerning NARR's representation of NAM.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0030, 10.1175/2010JCLI3593.1
Format: Citation

Title: Recent historically low global tropical cyclone activity.
Creator: Maue, Ryan Nicholas
Abstract/Description: Tropical cyclone accumulated cyclone energy (ACE) has exhibited strikingly large global interannual variability during the past 40-years. In the pentad since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s. Additionally, the global frequency of tropical cyclones has reached a historical low. Here evidence is presented demonstrating that considerable variability in tropical cyclone ACE is associated with the...
Show moreTropical cyclone accumulated cyclone energy (ACE) has exhibited strikingly large global interannual variability during the past 40-years. In the pentad since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s. Additionally, the global frequency of tropical cyclones has reached a historical low. Here evidence is presented demonstrating that considerable variability in tropical cyclone ACE is associated with the evolution of the character of observed large-scale climate mechanisms including the El Niño Southern Oscillation and Pacific Decadal Oscillation. In contrast to record quiet North Pacific tropical cyclone activity in 2010, the North Atlantic basin remained very active by contributing almost one-third of the overall calendar year global ACE.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0039, 10.1029/2011GL047711
Format: Citation

Title: Quantifying variance due to temporal and spatial difference between ship and satellite winds.
Creator: May, J., Bourassa, Mark
Abstract/Description: Ocean vector winds measured by SeaWinds can be validated with comparison in situ data that are within a certain time and space range to the satellite overpass. The total amount of random observational error is composed of two primary components, which are quantified in this study: the uncertainty associated with the data sets and the uncertainty associated with the temporal and/or spatial difference between two observations. The variance associated with a temporal difference, which can be...
Show moreOcean vector winds measured by SeaWinds can be validated with comparison in situ data that are within a certain time and space range to the satellite overpass. The total amount of random observational error is composed of two primary components, which are quantified in this study: the uncertainty associated with the data sets and the uncertainty associated with the temporal and/or spatial difference between two observations. The variance associated with a temporal difference, which can be translated into a spatial difference using Taylor's hypothesis, between two observations is initially examined in an idealized case that includes only Shipboard Automated Meteorological and Oceanographic System (SAMOS) 1 min data. The results show that the amount of variance in wind speed and direction increases as the time difference increases, while the amount of variance in wind speed increases and direction decreases with larger wind speeds. Collocated SeaWinds and SAMOS observations are used to determine the total amount of variance associated with a temporal (equivalent) difference from 0 to 60 min. For combined differences less than 25 min (equivalent) and the selected wind speed bins, the variance associated with the temporal and spatial difference is dominated by small changes in the wind speed distribution, and the sum of the observational errors is approximately 1.0 m2 s-12 (12 deg2) and 1.5 m2 s-2 (10 deg2) for wind speeds between 4 and 7 m s-1 and 7-12 m s-1. For larger combined differences, the observational error variance is no longer the dominant term; therefore, the total variance is seen to gradually increase with increasing time differences.
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Date Issued: 2011
Identifier: FSU_migr_coaps_pubs-0024, 10.1029/2010JC006931
Format: Citation

Title: Spatiotemporal Variability and Prediction of Rainfall over the Eastern Caribbean.
Creator: Pologne, Lawrence, Cai, Ming, Krishnamurti, T. N., Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Recent, recurrent, and extreme weather events have been a cause for concern over the Eastern Caribbean (EC). Given the dependence on rainfall of agriculture, the main stay of the fragile economies throughout the region, accurate and timely forecasts of seasonal rainfall need to be issued to facilitate decision making in Water Resource Management. Understanding the causes of climate variability can lead to the development of more robust models for climate prediction. So as a diagnostic...
Show moreRecent, recurrent, and extreme weather events have been a cause for concern over the Eastern Caribbean (EC). Given the dependence on rainfall of agriculture, the main stay of the fragile economies throughout the region, accurate and timely forecasts of seasonal rainfall need to be issued to facilitate decision making in Water Resource Management. Understanding the causes of climate variability can lead to the development of more robust models for climate prediction. So as a diagnostic approach, different techniques are employed. Empirical Orthogonal Function (EOF) analysis is performed in order to isolate the different modes of rainfall variability as well as investigating their amplitudinal modulations. The evolution of external forcing mechanisms that impact on precipitation extremes is also investigated with the use of composites. Based on the strength of the relationship between Sea Surface Temperature Anomalies (SSTA) and EC rainfall, a statistical model is subsequently developed using multivariate Canonical Correlation Analysis (CCA) to predict rainfall over the region on seasonal time scales. The CCA model demonstrated useful skill in predicting seasonal rainfall over the EC up to six months lead. The highest average predictive skill is realized for the June-July-August (JJA) season at one-month lead, while the lowest average skill is realized for the March-April-May (MAM) season at five months lead. The December-January-February (DJF) season maintained steady skill throughout six months lead. Below normal conditions are forecasted by the CCA model for the 2004/2005 dry season (DJF/2004-05, MAM/2005). This outlook is in part, verified from seasonal rainfall totals at two stations within the EC. The outlook for the coming rainy season is for above normal conditions.
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Date Issued: 2005
Identifier: FSU_migr_etd-0510
Format: Thesis

Title: Assessment of Groundwater Discharge to Lake Barco via Radon Tracing.
Creator: Stringer, Christina Elaine, Burnett, William C., Chanton, Jeffrey P., Sturges, Wilton, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Groundwater-surface water interactions in lakes have been gaining attention in recent years as scientists have recognized the potential significance that groundwater has as a source of nutrients and contaminants to aquatic ecosystems. Such interactions need to be understood in order for us to protect important ecosystems and quantify nutrient loading into lakes. This project set out to test the idea that good estimates could be made of groundwater inputs into Florida lakes using a simple...
Show moreGroundwater-surface water interactions in lakes have been gaining attention in recent years as scientists have recognized the potential significance that groundwater has as a source of nutrients and contaminants to aquatic ecosystems. Such interactions need to be understood in order for us to protect important ecosystems and quantify nutrient loading into lakes. This project set out to test the idea that good estimates could be made of groundwater inputs into Florida lakes using a simple geochemical tracer technique. We hypothesize that a relatively small number of measurements would be sufficient to provide a reasonably good (a factor of 2) estimate of groundwater discharge. Naturally occurring 222Rn makes an ideal tracer because it exists in enriched concentrations in groundwater relative to surface water. We used Lake Barco, a small seepage lake in the Katherine Ordway Preserve, for a detailed pilot study in order to test this hypothesis. The preserve is located about 34 km east of Gainesville, Florida and makes an excellent research site because it is maintained in a pristine state as it is closed off to public access. Two intensive samplings were completed, one in the "dry" season (March 2002) and one in the "wet" season (August 2003). In addition, periodic sampling trips were made to the lake every few weeks to evaluate the spatial and temporal patterns of radon distribution. A 222Rn mass balance was constructed for the lake to evaluate radon fluxes. Once the 222Rn fluxes were determined, groundwater inputs were estimated by dividing these fluxes by the concentration of radon in the water seeping into the lake. The radon concentration is estimated by sediment equilibration experiments using grab samples of sediment and radon activity measurements from monitor wells. We also constructed a traditional hydrologic water budget for Lake Barco. All hydrological variables were either measured or estimated and substituted into a water balance equation, which was then solved for the net groundwater flow term. These estimates were then compared to those from the 222Rn model. Our 222Rn measurements show little discernible spatial variation of radon inventories in the lake on any given day of sampling. Inventories measured at five different stations during the two different intensive sampling trips were all within ±13% of the mean value for each sampling. This amount of variation is considered insignificant, as the estimated analytical variation for the radon measurements is ±10%. We also found that we can estimate the lake inventory at any one station by collecting triplicate samples approximately one meter over the bottom at a single central sampling station. However, our results did display significant temporal variability, responding to rainfall trends that can influence the recharge rates. So, in a lake the size of Lake Barco (12 ha), reasonable groundwater discharge estimates at any given time can be made by triplicate analysis of radon in near-bottom waters and collection and processing of a few sediment samples. The estimations of groundwater discharge to the lake over the period of our study were, on average, 13,000 m3/month and 18,000 m3/month for the radon model and hydrologic budget, respectively. The water balance based estimate might be somewhat low due to differences in hydrogeologic movement under such dry conditions or the large error associated with budget estimations. Considering the large uncertainties in estimating groundwater flow via a hydrologic budget, agreement within a factor of two is considered satisfactory.
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Date Issued: 2004
Identifier: FSU_migr_etd-0395
Format: Thesis

Title: Metabolic Pathways in Natural Systems: A Tracer Study of Carbon Isotopes.
Creator: Prater, James L., Chanton, Jeffrey P., Wang, Yang, Kostka, Joel E., Mortazavi, Behzad, Burnett, William C., Winchester, John W., Department of Earth, Ocean and Atmospheric...
Show morePrater, James L., Chanton, Jeffrey P., Wang, Yang, Kostka, Joel E., Mortazavi, Behzad, Burnett, William C., Winchester, John W., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: The δ13C value of foliage respiration has been considered a constant in the past and modeling efforts have assumed that the δ13C value of foliage respiration is constant and is directly related to substrate without any fractionation. Consecutive δ13C measurements of foliage dark-respired CO2 (δ13Cr) for slash pine trees (Pinus elliottii) over several diel cycles were used to test the hypothesis that significant variation in δ13Cr would be observed. δ13Cr values collected in daylight from all...
Show moreThe δ13C value of foliage respiration has been considered a constant in the past and modeling efforts have assumed that the δ13C value of foliage respiration is constant and is directly related to substrate without any fractionation. Consecutive δ13C measurements of foliage dark-respired CO2 (δ13Cr) for slash pine trees (Pinus elliottii) over several diel cycles were used to test the hypothesis that significant variation in δ13Cr would be observed. δ13Cr values collected in daylight from all time series showed mid- day 13C enrichment (5 – 10‰) relative to bulk biomass, but values become more 13C depleted following shading and at night and approach bulk-biomass δ13C values by dawn. Assimilation model results suggest that respiration during daylight has the potential to significantly affect ∆13C by as much as 1.6‰, but night dark respiration has little impact on 24-hour integrated ∆13C (0.1‰). We also sampled methane and CO2 from collapse scar bogs (transient permafrost degradation features in permafrost peatlands) to test the hypotheses that microbial respiration and methane production are stimulated by permafrost degradation and collapse and that the fen-like vegetation (i.e. Carex andxi Eriophorum) found in collapse scar bogs near the collapsing edge stimulates acetate fermentation. Our results show that collapse scar bogs have an evolution of spatial variation in methanogenic pathways that is related to surface vegetation cover type. We also demonstrate that changes in stable-isotope fractionation caused by shifts from acetate fermentation and CO2 reduction occur over long time scales (> annual) and are dependent on changes in wetland morphology and surface vegetation cover. We also used radiocarbon as a tracer to test the hypothesis that melting permafrost surrounding the collapse scar bog provides nutrients to the bog-moat location, stimulating the production of radiocarbon-depleted methane. Our results show that the radiocarbon content of methane and DIC at these sites is highly variable and may depend on groundwater input, surface vegetation, and morphological factors associated with the melting permafrost plateau. We conclude that the younger, more labile, carbon stimulating acetate fermentation at one of the sites is supplied by the fen-like surface vegetation, while the older, more recalcitrant, carbon stimulating CO2 reduction at the other site may be supplied by melting permafrost plateau..
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Date Issued: 2005
Identifier: FSU_migr_etd-0429
Format: Thesis

Title: Morphological Barrier Island Changes and Recovery of Dunes after Hurricane Dennis, St. George Island, Florida.
Creator: Priestas, Anthony Michael, Fagherazzi, Sergio, Stallins, J. Anthony, Kish, Stephen, Georgen, Jennifer, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A robust dune system is one of the principal factors in the protection of recreational and residential property within barrier islands. Storm surge from significantly large storm events may remove some or all of the dunes during overwash processes and deposit sediment as washover fans or terraces in the back-barrier. During the summer of 2005, Hurricane Dennis greatly overwashed much of the northwest barrier island chain along the Florida panhandle. The post-storm recovery of dunes and...
Show moreA robust dune system is one of the principal factors in the protection of recreational and residential property within barrier islands. Storm surge from significantly large storm events may remove some or all of the dunes during overwash processes and deposit sediment as washover fans or terraces in the back-barrier. During the summer of 2005, Hurricane Dennis greatly overwashed much of the northwest barrier island chain along the Florida panhandle. The post-storm recovery of dunes and morphological changes occurring after Hurricane Dennis within St. George Island State Park is investigated, in addition to the application of numerical methods as a supplemental tool in determining the post-storm "recovery state" of the barrier and envision morphologic trends. Dune recovery rates are estimated by calculating sediment volume changes of profiles through time. One-dimensional, spatial-series Fourier analysis of individual profiles are used to quantify the recovery and morphologic nature of secondary dunes. Two-dimensional Fourier analysis of elevation data were attempted to be used as a tool to discriminate geomorphic trends in the barrier. Digital elevation models are used to describe post-storm morphologic changes, and the future recovery state of the barrier may be supplemented by analyzing the distributions of curvature and gradients calculated numerically from LIDAR data. Results show that secondary dunes recovered at an average rate of ~3-4 cm per month, and sediment volume changes across transects varied between -1.5 m3/m to1.2 m3/m depending on the presence of vegetation, storm-debris pavement, and proximity to washover deposits. Despite some transects having a net sediment volume loss, all dunes in the presence of vegetation had increased in height. Vegetation did not propagate where storm-debris pavement existed during the one-year duration of the study. The presence of vegetation inhibited dune migration thus favoring dune growth or decreasing the effect of erosion from strong wind events. Fourier analysis of profiles captured changes in dune height at specific wavelengths. The highest energies from the spectra were usually at 30 to 40 meter wavelengths for each profile in time, which reflects the immobility of the dunes and may also reflect the controls of vegetation on dune spacing. The results of two-dimensional Fourier analysis on terrain data were difficult to interpret, but may prove a potential use in terrain analysis. Overwash was prevalent throughout the barrier. For the studied area, St. George Island had experienced inundation overwash with an estimated 100,000 ft3/ft net loss of sediment following the hurricane. Nearly the entire foredune complex was removed, save a few remnants. Storm surge had likely penetrated first in areas where foredunes were either low or discontinuous; in these areas, beach widening was less prevalent. In contrast, the beach widening (~30ft) occurred in areas where the foredunes were higher and more continuous.
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Date Issued: 2009
Identifier: FSU_migr_etd-0458
Format: Thesis

Title: Ecology of Phytoplankton, Acartia Tonsa, and Microzooplankton in Apalachicola Bay, Florida.
Creator: Putland, Jennifer Nancy, Iverson, Richard, Wise, Sherwood, Marcus, Nancy, Kostka, Joel, Mortazavi, Behzad, Department of Earth, Ocean and Atmospheric Sciences, Florida State...
Show morePutland, Jennifer Nancy, Iverson, Richard, Wise, Sherwood, Marcus, Nancy, Kostka, Joel, Mortazavi, Behzad, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: Apalachicola Bay is a productive estuary located in the northern Gulf of Mexico. The high productivity is, in part, the result of the Apalachicola River delivering freshwater and nutrients to the Bay. Nutrient input supports high levels of phytoplankton productivity, which supports the Bay's secondary productivity. Diversion of water from headwaters of the Apalachicola River during summer has been proposed to satisfy upstream freshwater requirements for recreation and agriculture. Knowledge...
Show moreApalachicola Bay is a productive estuary located in the northern Gulf of Mexico. The high productivity is, in part, the result of the Apalachicola River delivering freshwater and nutrients to the Bay. Nutrient input supports high levels of phytoplankton productivity, which supports the Bay's secondary productivity. Diversion of water from headwaters of the Apalachicola River during summer has been proposed to satisfy upstream freshwater requirements for recreation and agriculture. Knowledge of the ecology of phytoplankton and zooplankton in the Bay is needed to help predict the effects of upstream water diversion on Apalachicola Bay. In this study, the temporal and spatial distribution of phytoplankton size composition, growth, biomass, productivity, microzooplankton bacterivory, herbivory, production, and Acartia tonsa herbivory, carnivory, egg production rate, and egg production efficiency were determined in Apalachicola Bay during 2003 and 2004. Phytoplankton growth, biomass, productivity, total ingestion rates and production rates of microzooplankton, and total ingestion rates and egg production rates of Acartia tonsa peaked during summer within lower salinity (psu) waters. Microzooplankton ingested, on average, ten times more phytoplankton productivity than A. tonsa. Compared to the 24 year average river discharge, river discharge into Apalachicola Bay was above average during 2003 and below average during 2004. On average, 100% and about 50% of the surface salinity of the Bay was 2004, respectively. Nutrient concentrations, at a specific salinity, were higher during 2003 than during 2004. Phytoplankton growth and productivity, as well as total ingestion rates and production rates of microzooplankton, at a specific salinity, were higher during summer 2003 than during summer 2004. It is expected that withdrawal of freshwater from the Apalachicola River during summer will lead to reduced higher trophic level production in Apalachicola Bay because of (1) reduced productivity of phyto- and microzooplankton at a specific salinity and (2) increased areal extent of higher salinity water (>20 psu) where phytoplankton growth, biomass, and productivity and zooplankton productivity is low. Implications of these results are also discussed with respect to our understanding of estuarine planktonic food web structure.20 psu) where phytoplankton growth, biomass, and productivity and zooplankton productivity is low. Implications of these results are also discussed with respect to our understanding of estuarine planktonic food web structure.
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Date Issued: 2005
Identifier: FSU_migr_etd-0505
Format: Thesis

Title: Multiple Isotopic Tracers for Study of Coastal Hydrological Processes.
Creator: Dulaiova, Henrieta, Burnett, William C., Donoghue, Joseph F., Chanton, Jeffrey P., Landing, William M., Moore, Willard S., Kostka, Joel E., Department of Earth, Ocean and...
Show moreDulaiova, Henrieta, Burnett, William C., Donoghue, Joseph F., Chanton, Jeffrey P., Landing, William M., Moore, Willard S., Kostka, Joel E., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: This study focused on the combined use of radon and radium isotopes as tracers of near-shore geophysical processes including submarine groundwater discharge (SGD), water exchange rates, and atmospheric evasion. Methods were developed for easier measurement of long-lived radium isotopes in natural waters and for continuous radon surveying over larger areas in the coastal zone. These tracer techniques were used to study the mentioned processes at study sites in Shelter Island Sound (New York),...
Show moreThis study focused on the combined use of radon and radium isotopes as tracers of near-shore geophysical processes including submarine groundwater discharge (SGD), water exchange rates, and atmospheric evasion. Methods were developed for easier measurement of long-lived radium isotopes in natural waters and for continuous radon surveying over larger areas in the coastal zone. These tracer techniques were used to study the mentioned processes at study sites in Shelter Island Sound (New York), the Gulf of Thailand, and Apalachicola Bay, Florida. Groundwater fluxes calculated for Shelter Island using isotopic techniques produced results consistent with those measured directly via seepage meters. Groundwater discharge in the Chao Phraya Estuary (Thailand) was shown to be in the range of 2 to 20 m3/s, small compared to river discharge but much higher than seepage rates measured in nearby locations. An experimental assessment of Rn-222 evasion to the atmosphere was performed using radon and Ra-224 profiles in the Chao-Phraya Estuary in Thailand. The different trends in radium and radon isotopes measured in the estuary provided an estimate of atmospheric exchange that agreed with a theoretical approach. Short-lived radium isotopes were applied in a seasonal study of water residence time in Apalachicola Bay, Florida. The water transport within different sectors of the bay was evaluated as a result of advective (estuarine) and dispersive physical mixing. The distribution of the radium isotope ratios was used to determine apparent radium ages of the water within the bay. The results clearly showed how the water-residence time in the bay changes seasonally and that the winds and tides influence the water circulation in the bay. The radium tracer approach gave turnover times of 6 to 12 days in Apalachicola Bay during the studied periods.
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Date Issued: 2005
Identifier: FSU_migr_etd-0643
Format: Thesis

Title: Interannual Flow off Southern California and Its Influence on Water Properties and Marine Life.
Creator: Dottori, Marcelo, Clarke, Allan J., Tam, Christopher, Nof, Doron, Weatherly, Georges, Dittmar, Thorsten, Department of Earth, Ocean and Atmospheric Sciences, Florida State...
Show moreDottori, Marcelo, Clarke, Allan J., Tam, Christopher, Nof, Doron, Weatherly, Georges, Dittmar, Thorsten, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: Lagged correlation of dynamic height from the gappy California Cooperative Oceanic Fisheries Investigation (CalCOFI) with monthly San Diego sea level for the period 1949-2001 shows that the dynamic height propagates westward at 4.10 cm/s, about double the speed of the large-scale low frequency Rossby wave (2.2 cm/s). TOPEX/Poseidon/Jason1 along-track sea level height estimates since January 1993, filtered interannually, propagate westward at 4.3 cm/s, verifying that observed westward...
Show moreLagged correlation of dynamic height from the gappy California Cooperative Oceanic Fisheries Investigation (CalCOFI) with monthly San Diego sea level for the period 1949-2001 shows that the dynamic height propagates westward at 4.10 cm/s, about double the speed of the large-scale low frequency Rossby wave (2.2 cm/s). TOPEX/Poseidon/Jason1 along-track sea level height estimates since January 1993, filtered interannually, propagate westward at 4.3 cm/s, verifying that observed westward propagation is about double that expected. Including the effect of the mean California current on the Rossby wave propagation does not explain the discrepancy but rather slightly increases it. Because of the westward propagation, interannual variations in alongshore geostrophic surface current are proportional to the time derivative of sea level. This means that such large scale interannual current variability can be monitored with appropriate lag, by the time derivative of coastal sea level. The anomalous alongshore flow advects particles, the anomalous alongshore particle displacement being proportional to sea level. Since nutrient concentration is lower in the south, the anomalous alongshore displacement results in lower nutrient concentration when sea level is anomalously high and higher nutrient concentration when the sea level is anomalously low. Vertical displacement also results in a similar relationship between nutrients and sea level. The anomalous alongshore and vertical particle displacements associated with the Rossby waves also act on the mean temperature and salinity fields to produce temperature and salinity anomalies. Theory suggests that these anomalies should be proportional to the anomalous dynamic height. Consistent with this, observed salinity anomalies at depths of 100-200 m are well correlated with dynamic height anomalies. At depths greater than 200 m the observed anomalies are small and, consistent with a smaller signal to noise ratio, the correlation falls. At depths shallower than 100 m the correlation between salinity and dynamic height anomalies also falls rapidly. The flow anomalies can similarly be used to explain the temperature fluctuations except that the correlation between temperature and dynamic height fluctuations does not fall rapidly in the surface layer as in the salinity case.
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Date Issued: 2007
Identifier: FSU_migr_etd-0684
Format: Thesis

Title: Statistical Prediction of Tropical Cyclone Intensity Using Dynamical and Thermodynamical Inner-Core Parameters Derived from Hwrf Analysis and Forecasts.
Creator: Zelinsky, David A., Co-, T.N. Krishnamurti, Co-, Paul Ruscher, Misra, Vasu, Hart, Robert, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A new multiple linear regression model for short range tropical cyclone intensity prediction is developed. Four new dynamical and thermodynamical predictors based on HWRF output are considered: (1) the horizontal advection of relative angular momentum, (2) energy exchange from the divergent to the rotational kinetic energy (Psi-Chi interactions), (3) the conversion of shear vorticity to curvature vorticity, and (4) the vertical differential of heating in the complete potential vorticity...
Show moreA new multiple linear regression model for short range tropical cyclone intensity prediction is developed. Four new dynamical and thermodynamical predictors based on HWRF output are considered: (1) the horizontal advection of relative angular momentum, (2) energy exchange from the divergent to the rotational kinetic energy (Psi-Chi interactions), (3) the conversion of shear vorticity to curvature vorticity, and (4) the vertical differential of heating in the complete potential vorticity equation. Predictors were calculated using Hurricane Research Weather and Forecast (HWRF) model initial fields. Each predictor was determined to exhibit a statistically significant relationship with 12 hour intensity change in tropical cyclones by an F-test. The predictors were then used as the basis for a multiple linear regression model, following the methodology of the operational Statistical Hurricane Intensity Prediction Scheme (SHIPS). Four additional predictors, intended to represent basic storm information and environmental conditions, were included in the development of a second model. Retrospective forecasts of hurricanes in 2004, 2005, and 2006 were created for both models, and compared to operational SHIPS and HWRF forecasts. Despite relying on HWRF fields for the calculation of predictors, the new model produces better forecasts than HWRF for short term (less than 48-hr) forecasts. Additional methods were developed to extend forecasts beyond 48 hours. This resulted in a systematic improvement of HWRF forecasts. It is proposed that the new model could be used operationally as a new version of the "early" HWRF.
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Date Issued: 2011
Identifier: FSU_migr_etd-0585
Format: Thesis

Title: Effect Hypoxia Has on Feeding and Egg Production Rates of Acartia Tonsa Dana 1849 (Copepoda: Calanoida).
Creator: Sedlacek, Chris, Marcus, Nancy, Thistle, David, Kostka, Joel, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Low oxygen conditions in the water column or hypoxia occur in estuaries and impact more than just the obvious commercially important species. Copepods are an important link in the food web and the influence of hypoxia upon them is relatively unstudied. Using the copepod Acartia tonsa, a study of the impact of hypoxia on egg production and feeding was conducted. A. tonsa decreased egg production at lower dissolved oxygen concentrations (DO), with the lowest egg production occurring at 0.53-ml...
Show moreLow oxygen conditions in the water column or hypoxia occur in estuaries and impact more than just the obvious commercially important species. Copepods are an important link in the food web and the influence of hypoxia upon them is relatively unstudied. Using the copepod Acartia tonsa, a study of the impact of hypoxia on egg production and feeding was conducted. A. tonsa decreased egg production at lower dissolved oxygen concentrations (DO), with the lowest egg production occurring at 0.53-ml/l O2 concentration. However as the DO decreased the amount of chlorophyll a in the gut of the copepods increased. Also as DO decreased the number of fecal pellets decreased, indicating that feeding was being suppressed. Another experiment was conducted to determine if by increasing food concentration the affect of hypoxia could be mitigated. The results indicate that increased food did not offset the impact hypoxia has on egg production of A. tonsa. These results suggest that as A. tonsa experiences hypoxia in the wild, population numbers will decrease. Thus if hypoxic conditions increase in scope and duration declines in copepod abundance may very well lead to a decline in the abundance of species that depend on them as food. These species may be of commercial importance.
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Date Issued: 2003
Identifier: FSU_migr_etd-0285
Format: Thesis

Title: The Impacts of Macrobenthos on the Rates and Pathways of Organic Matter Mineralization in Two Coastal Marine Ecosystems of the Southeastern United States.
Creator: Smith, April Christine, Kostka, Joel E., Balkwill, David, Thistle, David, Marcus, Nancy, Devereux, Richard, Furukawa, Yoko, Department of Earth, Ocean and Atmospheric Sciences,...
Show moreSmith, April Christine, Kostka, Joel E., Balkwill, David, Thistle, David, Marcus, Nancy, Devereux, Richard, Furukawa, Yoko, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: Coastal ecosystems are among the most productive in the world, and they serve as an invaluable resource to society. Despite many decades of biogeochemical research in the coastal zone, carbon and nutrient budgets remain uncertain largely due to the inherent complexity and spatiotemporal variability observed in coastal ecosystems. This dissertation addresses the rates, pathways, and microorganisms responsible for organic-matter mineralization and nutrient release in the sediments of coastal...
Show moreCoastal ecosystems are among the most productive in the world, and they serve as an invaluable resource to society. Despite many decades of biogeochemical research in the coastal zone, carbon and nutrient budgets remain uncertain largely due to the inherent complexity and spatiotemporal variability observed in coastal ecosystems. This dissertation addresses the rates, pathways, and microorganisms responsible for organic-matter mineralization and nutrient release in the sediments of coastal marine ecosystems. In particular, the research herein focuses on the role of macrobenthos and spatial/ temporal variability in impacting organic matter and nutrient cycles in such ecosystems. The common theme throughout the dissertation research was to combine ecology with biogeochemistry to explore the impacts of benthic organisms in the macroscale on microbial processes that mediate organic matter mineralization and nutrient release over the microscale. Sulfate-reducing prokaryotes (SRP) play a key role in carbon and nutrient cycles of coastal marine, vegetated ecosystems, but interactions of SRP communities with aquatic plants remain little studied. In the subtidal zone of Santa Rosa Sound, Florida, SRP abundance, activity, and community composition were studied in relation to sediment geochemical gradients and plant growth state in a Thalassia testudinum seagrass bed and in adjacent unvegetated areas (Chapter 1). The community composition of SRP was determined using restriction fragment length polymorphism (RFLP) screening and amino acid sequence comparisons inferred from partial dissimilatory bisulfite reductase (dsrA and B) genes that were PCR-amplified and cloned from DNA extracted from sediment samples. Our results indicate that seagrass growth state affects the abundance and activity of SRP, while SRP community composition remains relatively stable across the environmental parameters tested. Sequence data from this study may be used to direct future cultivation efforts and to design new genetic probes for sulfate-reducers in seagrass sediments. The remaining dissertation research focused on a second coastal marine ecosystem, the saltmarsh, on Skidaway Island near Savannah, Georgia. The Georgia saltmarsh contrasts with seagrass beds from the west coast of Florida in that it exists in the intertidal zone, contains a large tidal range of 2-3 m, and the sediments are exposed to extensive burrowing and feeding activities by macrofauna. In addition, larger seasonal change may be observed in the Georgia marsh because it is intertidal and exposed to slightly larger annual temperature extremes. In chapter two, extensive biogeochemical field characterization was combined with state-of-the-art diagenetic modeling to elucidate feedbacks between macrobenthic organisms (macrophyte plants, bioturbating macrofauna) and the controls of organic matter mineralization in saltmarsh sediments. A multicomponent, inverse model was used to support the field work by quantifying properties and processes that in some cases could not be experimentally determined. Modeled rates of organic matter diagenesis were determined by attempting to find the best agreement with measured profiles of major redox species. Results indicated that sulfate reduction is the dominant degradation pathway for sites with less bioturbation, while iron reduction outcompeted sulfate reduction where intense bioturbation activity caused the rapid recycling of Fe(III)-oxyhydroxides. These results were fairly consistent across seasons, however, the magnitude of degradation rates decreased dramatically in the winter, and microbial sulfate reduction was more greatly affected by changes in temperature than microbial iron reduction. The objective of the third and final study was to scale up biogeochemical measurements over an entire ecosystem (saltmarsh basin) in order to address spatial variability that has confounded estimates of organic matter and nutrient mineralization at the whole ecosystem level. A 100,000 m2 area of Georgia marsh was mapped using a combination of aerial photography, Geographic Information Systems (GIS), and localized identification of plant types. Major habitats were delineated according to the predominant vegetation, including the short form of Spartina alterniflora (SS), the tall form of S. alterniflora (TS) and unvegetated creekbank (CB). Spatial variability was addressed across all major habitats with a statistically-sound experimental design to carry out determinations of porewater and solid-phase geochemistry, sulfate reduction rates (SRR), bacterial abundances, macrofaunal burrow size/density, plant stem height/density, and above/belowground plant biomass. Habitat type had a large influence on the rates and pathways of carbon oxidation. Consideration of spatial variability revealed that overall carbon oxidation rates in saltmarsh ecosystems may be higher than previously thought. Surprisingly, microbial Fe(III) reduction (and not sulfate reduction) was observed to be the predominant terminal-electron-accepting process coupled to carbon oxidation for the majority of the marsh basin studied. Together with the observation that most of the Georgia marsh studied was not sulfidic, results indicate that our perceptions of the redox poise, and the impacts of redox poise on biogeochemical cycles, need to be revised for marsh ecosystems taking into account spatial variability driven by macrobenthic activities. Typically, coastal sediments rapidly become anaerobic just below the sediment surface, and the flux of oxidants into sediments is limited. Under these conditions, anaerobic bacteria are responsible for the majority of organic matter remineralization. Increased solute and particle transport via macroorganismal activities (bioturbation, bioirrigation, and phytoirrigation) aids in mixing reactants throughout sediments, thereby encouraging microbial activities, and increasing organic matter remineralization rates. The following research employed an array of new and diverse multidisciplinary approaches from molecular biological techniques and GIS mapping to state-of-the-art diagenetic modeling in order to elucidate the impacts of macrobenthos on carbon and nutrient cycles mediated by anaerobic microorganisms in coastal marine ecosystems. In all three studies, geochemical parameters indicated that bacterial activities were stimulated in vegetated sediments, while saltmarsh studies revealed that macrofaunal burrows strongly influenced the pathways of terminal electron acceptor (TEA) usage. The uncertainty of current estimates of carbon and nitrogen cycling in saltmarsh habitats indicates the need for a more comprehensive approach to address the spatial variability that exists in these habitats. From the research reported in this dissertation, it is clear that macrobenthos have a profound impact on the rates and pathways of organic matter mineralization and that the resulting spatial variability in sediment biogeochemical cycles must be incorporated into future studies that attempt to determine elemental budgets in coastal marine ecosystems.
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Date Issued: 2004
Identifier: FSU_migr_etd-0343
Format: Thesis

Title: The Bering Strait and the Southern Ocean Winds' Grip on the World Climate.
Creator: De Boer, Agatha M., Nof, Doron, Hunter, Christopher, Burnett, William, Clarke, Alan J., Speer, Kevin, Weatherly, Georges L., Department of Earth, Ocean and Atmospheric Sciences,...
Show moreDe Boer, Agatha M., Nof, Doron, Hunter, Christopher, Burnett, William, Clarke, Alan J., Speer, Kevin, Weatherly, Georges L., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: The Bering Strait's Grip On The World Climate: The Holocene interglacial period of the last 10,000 years and the penultimate interglacial ~125,000 years ago have been characterized by distinctly stable climates. During the intervening glacial period, climate records are marked by rapid large-amplitude oscillations, general known as Dansgaard-Oeschger events. These millennial-scale cycles are generally believed to be a result of freshwater anomalies in the North-Atlantic, followed by a...
Show moreThe Bering Strait's Grip On The World Climate: The Holocene interglacial period of the last 10,000 years and the penultimate interglacial ~125,000 years ago have been characterized by distinctly stable climates. During the intervening glacial period, climate records are marked by rapid large-amplitude oscillations, general known as Dansgaard-Oeschger events. These millennial-scale cycles are generally believed to be a result of freshwater anomalies in the North-Atlantic, followed by a reorganization of the thermohaline circulation. Here, we propose that such long lasting instabilities in the thermohaline circulation are only possible during glacial periods when the Bering Strait (BS) is closed. A semi-global analytical ocean model (which includes both wind and thermohaline processes) is used to show that, during interglacial periods (when the BS is open) perturbations in North Atlantic Deep Water (NADW) formation are rapidly damped out because of a novel BS freshwater feedback mechanism. This new feedback mechanism is due to the strong winds in the Southern Ocean (SO) which, with an open BS, quickly [O(10)years)] flush any low salinity anomalies out of the Atlantic and into the Pacific Ocean. During glacial periods, the stabilizing feedback is prevented by the closure of the BS which traps the anomalies within the Atlantic, causing long lasting perturbations. The sensitivity of the mean stable state to steady changes in the external forcing, namely the wind or the precipitation field, is also tested. A relevant example is a prolonged increase in precipitation due to anthropogenic warming, (predicted by global circulation models). We find that both stronger winds (especially the SO Winds) and a decrease in precipitation over the North Atlantic (NA) will lead to a new (stable) enhanced overturning. Conversely, weaker winds or increased precipitation will reduce the overturning to a slower stable state. The Island Wind-Bouyancy Paradox: In reent years, a variety of studies have suggested that the meridional overturning circulation is at least partially controlled by the Southern Ocean winds. The paraadoxical implication is that a link exists between the surface bouyancy flux to the ocean (which is needed for the density transfor4matio between surface and deep water) and the wind. These forcings have traditionally been viewed as independent drivers of the ocean circulation. Here, the paradox is formally stated in the framework of a gigantic island that lies between latitude bands free of continents (such as the land mass of the Americas). The choice of such an island on a sphere was made because it enables one to obtain analytical solutions and it circumvents the need to calculate the torque exerted on zonal sills adjacent to the island tips (e.g., the Bering Strait). The torque calculation is notoriously difficult and is avoided here by the clockwise integration which goes twice through the western boundary of the island (in opposite directions) eliminating any unknown pressure torques. The derived wind-driven overturning is shown to be consistent with Godfrey's Island Rule when the rule is extended to include the sinking or upwelling adjacent to the island. In addition, the consideration of vertical exchange in the Island Rule eliminates the need to make the level-of-no-motion assumption. The paradox is resolved quanlitatively, using salinity and temperature mixed dynamical-box models and a temperature slab model, and quantitatively, employing a numerical model. We show that in all cases the ocean stratification and thermocline depth adjust themselves to allow the overturning imposed by the wind. The salinity and temperature box model suggests that stronger southern winds will tend to weaken the virtical and horizontal salinity stratfication so that it is esier for the conversion of deep to surface water (and vice versa) to take place. A temperature slab model (i.e., y-dependent)offers a more detailed picture;stronger southern winds flatten the meridional temperature profile and shift it northwards (so that it lags the atmospheric temperature). The (process orientated) numericl model is adapted to include a thermodynamic parameterization for the surface heat and freshwater fluxes. In response to stronger southern winds, the thermocline thickens in the north, releases more heat to the atmosphere and, therefore, converts more surface to deep water.
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Date Issued: 2003
Identifier: FSU_migr_etd-0336
Format: Thesis

Title: Attributing Contributions to the Seasonal Cycle of Anthropogenic Warming in a Simple Radiative- Convective Global Energy Balance Model.
Creator: Sejas, Sergio A., Cai, Ming, Ellingson, Robert G., Wu, Zhaohua, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: A simple one-dimensional seasonal atmosphere-ocean energy balance model is used to study the seasonal and latitudinal response of the model climate to a doubling of the CO2 concentration. A new climate feedback analysis method, formulated in Lu and Cai (2009a), is used to isolate contributions (partial temperature changes) of the external forcing alone and subsequent feedbacks to the total temperature change experienced by the model climate. In this study, the relative importance of the...
Show moreA simple one-dimensional seasonal atmosphere-ocean energy balance model is used to study the seasonal and latitudinal response of the model climate to a doubling of the CO2 concentration. A new climate feedback analysis method, formulated in Lu and Cai (2009a), is used to isolate contributions (partial temperature changes) of the external forcing alone and subsequent feedbacks to the total temperature change experienced by the model climate. In this study, the relative importance of the external forcing alone (the CO2 doubling), surface ice-albedo feedback, water vapor feedback, changes in poleward heat transport, changes in vertical sensible heat flux, and changes in heat storage are analyzed. The partial temperature change due to the water vapor feedback is substantially the largest contributor to the globally averaged surface warming. The ice-albedo feedback plays a smaller role, but also significantly contributes to the overall warming of the surface. The most important negative feedback, counteracting the surface warming, is the change in the vertical sensible heat flux. However, though the water vapor feedback is most responsible for the overall surface warming, it is not the feedback most responsible for the seasonal and spatial pattern of the surface warming. The climate of this model indicates that there is a surface polar warming amplification, with a maximum occurring in late summer/early fall. The feedback most responsible for this polar warming amplification and seasonal pattern in this model is the surface ice-albedo feedback, which is largest at high latitudes in summer.
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Date Issued: 2011
Identifier: FSU_migr_etd-0278
Format: Thesis

Title: Impacts of Deep-Sea Carbon Sequestration and of Ciliate Epibionts on Harpacticoid Copepods.
Creator: Sedlacek, Linda, Thistle, David, Wulff, Janie, Marcus, Nancy, Huettel, Markus, Burnett, William, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: One way to slow down global warming is to reduce the amount of carbon dioxide released into the atmosphere by capturing carbon dioxide from point sources (e.g., power plants) and storing it out of contact with the atmosphere. One storage site that is being considered is the deep-sea floor. Below ~2600 m, carbon dioxide is a liquid and is denser than seawater, so carbon dioxide poured into a depression would create a carbon dioxide lake. The environmental consequences of this disposal option...
Show moreOne way to slow down global warming is to reduce the amount of carbon dioxide released into the atmosphere by capturing carbon dioxide from point sources (e.g., power plants) and storing it out of contact with the atmosphere. One storage site that is being considered is the deep-sea floor. Below ~2600 m, carbon dioxide is a liquid and is denser than seawater, so carbon dioxide poured into a depression would create a carbon dioxide lake. The environmental consequences of this disposal option are largely unknown. This study tries to address the environmental consquences by studying the effects of carbon dioxide-rich seawater on organisms at various distance from a carbon-dioxide source. Harpacticoids were chosen as the study organism because they are abundant and may be an important prey item in the deep sea. To determine if the carbon dioxide-rich seawater affected the harpacticoids, a seven metrics were used. Overall, none of the metrics indicated that exposure to carbon dioxide-rich seawater had an effect. A previous study found a very different result. A comparison of the two studies revealed that the difference in flow dynamics between the two stations in the two experiments could explain the dichotomy, raising the possibility that deep-sea benthic environments that experience slower flow may be better disposal sites. Harpacticoids in the deep-sea sometimes harbor ciliate epibionts. Their presence may influence a harpacticoid's ability to deal with the stress imposed by carbon-dioxide rich seawater. As a first step in trying to understand the harpacticoid-epibiont relationship, I identified the epibionts and determined whether or not they occurred more frequently on adults, on one host species more than the others, on one host sex more than another, or on one portion of a host more than another portion at the control site. Three epibiont species were abundant enough to analyze, Loricophrya sp., Trachelolophos sp., and Vorticella sp. Loricophrya sp. and Trachelolophos sp. individuals attached only to the antennules of Nitokra sp. and occurred significantly more often on this species than on other species. Vorticella sp. individuals attached significantly more frequently to Ameira sp. and Mesocletodes cf. irrasus than to other species. Individuals of Vorticella sp. were found attached to the side of the cephalosome, to the region of the mouth parts, and to the body between the swimming legs. Specificity in host usage was unexpected because harpacticoid individuals of a given species are sparse in the deep-sea. I did not find that any of the epibiont species occurred on one sex more than the other. One method that epibionts may use in order to be host specific is to attach to species that are relatively abundant. I then examined the potential effect that the epibionts had on their hosts. To do so, I compared the harpacticoids at the 2-m site (treatment area) and 75-m site (control area). I found that only for individuals of Nitokra sp. with individuals of Loricophrya sp. attached was there a significantly higher proportion of host individuals with epibionts in the treatment area than in the control area. None of the host species showed a difference in the average number of epibionts they carried in the control area and the treatment area. These results suggest that individuals of Nitokra sp. were capable of resisting the attachment of the first individual of Loricophrya sp., but that individuals of Nitokra sp. were unable to continue to resist after the first Loricophrya sp. individual attached. Trachelolophos sp. was always with Loricophrya sp., so for the analyses that examined the proportion of host individuals that were alive at the time of collection, the group of harpacticoids that had only Loricophrya sp. (= L.) and those with both Trachelolophos sp. and Loricophrya sp. (= L. + T.) were analyzed together (= L. and L. + T.). In the treatment area, the proportion of individuals of Nitokra sp. that were alive at the time of collection was greater when individuals of L. and L. + T. were attached than when they not. In the control area, the proportion of individuals of Ameira sp. that were alive at the time of collection was greater when individuals of Vorticella sp. were attached than when they were not. In general, the effect of the epibionts on their host harpacticoids appears to be positive, an unexpected result considering that positive effects have not been found before.
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Date Issued: 2007
Identifier: FSU_migr_etd-0284
Format: Thesis

Title: The Biochemical Composition of Naupii Derived from Stored Non-Diapause and Diapause Copepod Eggs and the Biology of Diapausing Eggs.
Creator: Sedlacek, Christopher, Marcus, Nancy, Keller, Laura, Thistle, David, Huettel, Markus, Kostka, Joel, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Mariculture of fish is needed to support our ever growing global population. Copepods are a natural and beneficial source of first feed for many marine fish species, but it can be difficult to hatch enough when the fish are ready to feed. Therefore, storage of copepod eggs for use at a later date increases the potential of nauplii to be used as a commercial food source. There are two types of eggs produced by copepods: diapause and non-diapause (or subitaneous). However, little is known about...
Show moreMariculture of fish is needed to support our ever growing global population. Copepods are a natural and beneficial source of first feed for many marine fish species, but it can be difficult to hatch enough when the fish are ready to feed. Therefore, storage of copepod eggs for use at a later date increases the potential of nauplii to be used as a commercial food source. There are two types of eggs produced by copepods: diapause and non-diapause (or subitaneous). However, little is known about diapause or the effects and duration of storage, either under cold or warm temperature conditions, on the biochemical composition of nauplii. Little is also known about the development of embryos that enter diapause. Diapause requires a refractory period before development of the embryo continues. The refractory period can last for several months regardless of environmental conditions. I studied the effects of both cold storage and cold storage with the addition of antibiotics on non-diapause eggs of the copepod Acartia tonsa and duration of storage for diapause eggs produced by Centropages hamatus and compared those results to nauplii derived from non-diapause eggs. The organic components analyzed to determine if potential changes were occurring during storage were lipids, fatty acids, proteins, free amino acids, and carbohydrates as well as the percent hatch of the eggs and the dry weight of the resultant nauplii. To understand diapause, we utilized two stains, one to determine the number of nuclei present and another to determine intracellular pH of the diapausing eggs. Acartia tonsa eggs stored for up to15 days at 1°C did not indicate any change in the biochemical make-up of the resulting nauplii. The only change we observed was in the viability of the eggs, which decreased at a steady rate over time. The viability of the eggs quickly approached zero percent hatch beyond 15 days. The addition of the antibiotic oxytetracyclin at a 10% concentration did not change the naupliar biochemistry and did not increase viability over the storage time. Centropages hamatus eggs maintained a high level of viability over the course of 13 months of storage under anoxic conditions. The nauplii derived from the diapause eggs stored at 25°C had similar biochemical components regardless of the length of the storage period. My study indicates that storage of A. tonsa and C. hamatus may not affect the nutritional value of the nauplii for aquaculture purposes. We also determined that the embryos of C. hamatus stopped developing after ~7 cleavages. The diapausing embryos also maintained an intracellular pH similar to the surrounding water and acidified when beginning to develop. This is the first time the intracellular pH and only the third time the nuclei of a copepod diapausing egg has been determined. This information could allow future researchers to interrupt diapause and induce the eggs to hatch before the end of the refractory period.
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Date Issued: 2008
Identifier: FSU_migr_etd-0283
Format: Thesis

Title: Assimilation of GPS Radio Occultation Observations.
Creator: Shao, Hui, Zou, Xiaolei, Navon, Ionel M., Liu, Guosheng, Ray, Peter S., Krishnamurti, T. N., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Unlike conventional and satellite observations, the Global Positioning System (GPS) radio occultation (RO) techniques provide all-weather, high-vertical-resolution observations that require no calibration. In this dissertation, the assimilation of GPS RO data is studied using the National Centers for Environmental prediction (NCEP) three dimensional variational analysis system. Three GPS data assimilation choices are considered and compared. A set of GPS bending angle assimilation (BA)...
Show moreUnlike conventional and satellite observations, the Global Positioning System (GPS) radio occultation (RO) techniques provide all-weather, high-vertical-resolution observations that require no calibration. In this dissertation, the assimilation of GPS RO data is studied using the National Centers for Environmental prediction (NCEP) three dimensional variational analysis system. Three GPS data assimilation choices are considered and compared. A set of GPS bending angle assimilation (BA) experiments is first carried out and sensitivity of BA results to the observational weighting, the quality of the background fields, the variation of the gravity, and the vertical resolution of the GPS data are investigated. The GPS local refractivity assimilation (REF) is then conducted and compared with BA. Although REF is computationally cheaper than BA, the bias and root mean square errors of the background fields are more significantly reduced by BA than REF. Differences between GPS refractivity and bending angle assimilations are larger in thick-layered cloud systems (e.g., convective clouds in the mid-latitudes and cumulus clouds in the tropics) than in thin clouds and clear sky, which are found to be associated with the strength of horizontal gradient of the atmospheric refractivity. Aiming at achieving both accuracy and computational efficiency, a new observation operator that simulates the GPS excess phase delay is proposed and tested for GPS RO data assimilation. Using the excess phase delay, the along-track refractivity and refractivity gradient information can be included while the computational cost is kept low. Numerical results from the forward simulation and data assimilation using the excess phase delay (PHA) are compared with those of REF. PHA tends to produce a warmer and wetter model atmosphere, with finer structures and larger radii of influence than REF. Compared to GPS observations, simulations and analyses produced by PHA are more accurate than those of REF. It is also pointed out that under the assumption of the spherical symmetry of the local refractivity, the observation operator for the excess phase delay simplifies into a point scheme in which only a vertical profile of model refractivity is required.
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Date Issued: 2005
Identifier: FSU_migr_etd-0301
Format: Thesis

Title: Lightning Observations during Tropical Cyclone Intensity Change: A Composite Study of Spatial and Temporal Relationships.
Creator: Austin, Marcus, Fuelberg, Henry, Hart, Robert, Ruscher, Paul, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Although tropical cyclone (TC) track forecasts have improved considerably in recent years, predicting their intensity continues to be a challenge for both meteorologists and numerical models. A storm's path is primarily influenced greatly by large-scale atmospheric circulations; however, its strength appears to be dominated both by large scale influences and small-scale mechanisms within the storm itself. Most previous research on TC intensity change has employed either numerical modeling or...
Show moreAlthough tropical cyclone (TC) track forecasts have improved considerably in recent years, predicting their intensity continues to be a challenge for both meteorologists and numerical models. A storm's path is primarily influenced greatly by large-scale atmospheric circulations; however, its strength appears to be dominated both by large scale influences and small-scale mechanisms within the storm itself. Most previous research on TC intensity change has employed either numerical modeling or diagnostic approaches using traditional meteorological parameters. Only recently have studies begun to examine electrification as a means for assessing the potential for intensification. Several papers have considered lightning as a proxy for storm intensification, mostly using data from Vaisala's National Lightning Detection Network (NLDN) and Long-Range Lightning Detection Network (LLDN). However, they mostly have examined individual TCs. This study uses LLDN data to study 45 Atlantic Basin TCs between the years 2004 and 2008. Using the National Hurricane Center's (NHC) best track dataset, lightning data are collected for each TC out to a 500 km radius. Parameters including storm intensity, intensity change, environmental vertical wind shear, storm motion, and flash count are compiled at each NHC best track position. The data at each position then are categorized in several ways, including change in intensity. These methods allow us to examine relations between composites of storm intensity/intensification and convective distribution and frequency. Distributions of cloud-to-ground (CG) flash density with respect to storm motion and speed show that lightning generally is preferred in the TCs' right front and right rear quadrants. Hurricanes produce the greatest flash densities during relatively slow forward motion, while tropical depressions and tropical storms exhibit greater flash densities during faster forward motion. Storm-relative CG flash distributions during weakening, no pressure change, and slow intensification (-5 to 0 hPa 6 h-1) exhibit the same right front and rear quadrant preference as the TC intensity categories. Flash densities are greatest during periods of faster intensification, with a nearly symmetric presentation in the inner core region. When computing flash densities with respect to environmental deep layer wind shear, TCs exhibit a strong preference for lightning in the downshear left and right quadrants of the inner core (0-100 km) and outer rainbands (100-300 km), respectively. Tropical storms and hurricanes best show this relation, with TDs exhibiting a stronger preference for lightning in the downshear right quadrant. Relatively weak wind shear produces greater flash densities in all TC intensity categories. Conversely, storms experiencing strong shear exhibit smaller flash densities in all TC categories due to the disruption of deep convection. During periods of faster intensification, maximum flash densities are located in the inner core, with weakening, no change, and slow intensification periods containing greatest density in the outer rainbands. Average flash rates and flash densities are found to be greatest for weaker TCs (tropical depressions and tropical storms) with smaller flash rates and densities in hurricanes. Considering intensity change, periods of faster intensification exhibit significantly greater flash rates than periods of weakening, no pressure change, and slow intensification. Only weak relations are found between flash rates and intensity change, with the strongest relationship occurring when lightning lags (occurs after) the pressure change period. Lightning preceding (occurring before) the pressure change period exhibits the weakest relationships in all TC intensities. Correlations between CG lightning and sustained wind speed indicate that there is no preferred timing between maximum lightning activity and maximum sustained winds. Instead, maximum correlations occur during periods when greatest lightning activity both precedes and lags the maximum sustained wind. These results indicate that lightning is poorly correlated with intensity change and can be regarded as a poor choice for intensity forecasting.
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Date Issued: 2011
Identifier: FSU_migr_etd-0261
Format: Thesis

Title: Abundance of Bottlenose Dolphins (Tursiops Truncatus) in the Big Bend of Florida, St. Vincent Sound to Alligator Harbor.
Creator: Tyson, Reny Blue, Nowacek, Douglas, Dewar, William, Wells, Randy, Chanton, Jeffrey, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Mark-recapture surveys implementing photographic identification techniques were used to estimate the abundance of bottlenose dolphins in an area of the Big Bend of Florida, stretching from St. Vincent Sound to Alligator Harbor, in the summer of 2007 and winter of 2008. The current population size of individuals in this region is unknown as the most recent abundance estimates were calculated based on aerial surveys conducted in 1993. Recent large scale mortality events, together with an...
Show moreMark-recapture surveys implementing photographic identification techniques were used to estimate the abundance of bottlenose dolphins in an area of the Big Bend of Florida, stretching from St. Vincent Sound to Alligator Harbor, in the summer of 2007 and winter of 2008. The current population size of individuals in this region is unknown as the most recent abundance estimates were calculated based on aerial surveys conducted in 1993. Recent large scale mortality events, together with an increasing potential for human impacts in this area, warrant an updated and increased understanding of the abundance and stock structure of dolphins in this region. Because the region is large and recent work here suggests that at least two distinct communities exist in these waters, the region was divided into the two areas in which these communities appear to reside (St. Vincent Sound/Apalachicola Bay and St. George Sound/Alligator Harbor) and independent estimates of abundance were calculated for each area and each season. Closed-population models in the program CAPTURE were used to derive the estimates of abundance and the assumptions underlying each model were examined. The estimates calculated from the models selected as being the most appropriate for each data set were similar for each survey area for each season: in the St. Vincent Sound/Apalachicola Bay survey area 182 ± 58 animals inhabited the survey area in the summer and 178 ± 77 animals in the winter; in the St. George Sound/Alligator Harbor survey area 365 ± 164 animals inhabited the survey area in the summer and 359 ± 87 animals in the winter. Results from this study also provided further evidence that at least two communities reside in these waters as only 2.4% of animals captured during the study were captured in both survey areas. If indeed two communities exist in these waters, it appears that site-fidelity and/or residence patterns of individuals may differ between them; in the St. Vincent Sound/Apalachicola Bay survey area 49.6% of the total animals captured were captured more than once and 29.6% were captured both seasons, while in the St. George Sound/Alligator Harbor survey area 35.3% were captured more than once and 13.8% of animals were captured both seasons. In addition, it appears that the St. George Sound/Alligator Harbor survey area supports a greater number of transient animals than the St. Vincent Sound/Apalachicola survey area (46.1% of distinctive animals were seen only once versus 29.9% respectively). This may be due in part to this survey area being more accessible to the open waters of the Gulf of Mexico than the St. Vincent Sound/Apalachicola Bay survey area, which is more protected by barrier islands. The results provided here can be used by the National Marine Fisheries Service to aid in their stock-assessment process and help in the management of the animals in this region.
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Date Issued: 2008
Identifier: FSU_migr_etd-0323
Format: Thesis

Title: Post-Processing Improvements to an Ensemble Forecast Using an Archive of Past Forecasts and Verifications.
Creator: Allgood, Adam Douglas, Ahlquist, Jon E., Krishnamurti, T. N., Zou, Xiaolei, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Ensemble forecasts are the primary tool used operationally to assess forecast uncertainty. Studies of ensemble forecasts, however, have shown that forecast verifications too frequently lie outside of the ensemble's range of possibilities, meaning that uncorrected ensemble forecasts suggest more confidence than is justified. To make ensemble forecasts more representative of the actual range of possibilities, we present a technique to post-process ensemble forecasts by replacing member...
Show moreEnsemble forecasts are the primary tool used operationally to assess forecast uncertainty. Studies of ensemble forecasts, however, have shown that forecast verifications too frequently lie outside of the ensemble's range of possibilities, meaning that uncorrected ensemble forecasts suggest more confidence than is justified. To make ensemble forecasts more representative of the actual range of possibilities, we present a technique to post-process ensemble forecasts by replacing member forecasts with verifications of what actually occurred when past forecasts were similar. To maximize the information that can be extracted from an archive of past forecasts and verifications, we allow analogs to come from different locations in space. We evaluated our procedure to post-process NCEP ensemble precipitation forecasts for the United States for 15-day periods in July 2005 and January 2006. Our analog correction technique significantly improved the ensemble's ability to forecast the probability of precipitation, in particular correcting the NCEP Global Ensemble's ``wet' bias at low precipitation amounts. Brier Skill Scores for 6-hour accumulated precipitation during the winter indicated that uncorrected ensemble forecasts were less skillful at predicting the probability of precipitation than forecasting zero precipitation as indicated by negative Brier Skill Scores (roughly -2.5). Post processed forecasts had Brier Skill Scores as high as 0.34. The tendency of the ensemble to underforecast heavy precipitation events, however, was not well corrected by our post-processing technique. Examinations of analog locations during heavy precipitation events indicated that analogs were taken from regions where precipitation patterns differed from those at the forecast point. This indicates that analogs must be chosen using more information than merely the similarity of ensemble precipitation forecasts to past forecasts.
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Date Issued: 2007
Identifier: FSU_migr_etd-0173
Format: Thesis

Title: Improving Hurricane Intensity Forecasts in a Mesoscale Model via Microphysical Parameterization Methods.
Creator: Albers, Cerese Marie, Krishnamurti, Tiruvalam N., Liu, Guosheng, Ruscher, Paul, Hood, Robbie, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Accurate hurricane intensity prediction is at the forefront of atmospheric science today, and improvements to mesoscale modeling of these storms continue to be major components of refining the accuracy of intensity forecasting. The primary goal of this study is to improve mesoscale modeling of hurricane intensity via the comparison of field campaign observations of Hurricane Erin 2001 from the Fourth Convection And Moisture Experiment (CAMEX-4) and Hurricane Dennis 2005 from the Tropical...
Show moreAccurate hurricane intensity prediction is at the forefront of atmospheric science today, and improvements to mesoscale modeling of these storms continue to be major components of refining the accuracy of intensity forecasting. The primary goal of this study is to improve mesoscale modeling of hurricane intensity via the comparison of field campaign observations of Hurricane Erin 2001 from the Fourth Convection And Moisture Experiment (CAMEX-4) and Hurricane Dennis 2005 from the Tropical Cloud Systems and Processes (TCSP) mission with simulated results of improved microphysical parameterization in a mesoscale model that utilizes the Krishnamurti, et al (1991) technique of rain rate initialization (RRI). Comparison of the simulated results with field observations collocated with satellite observations provides a way to validate many different aspects of the simulated hurricane's structure and intensity. The mesoscale model used in this research is the Weather Research & Forecasting (WRF) model version 2.1 (ARW). Much of the existing microphysical parameterization of this model is built from results of mid-latitude observations. Substantial improvement to the model's intensity forecasting in the tropics can be made via proper parameterization of the model microphysics for hurricanes. With a foundation of results from other hurricane mesoscale modeling initial/boundary conditions, dynamics and physics studies, basic options for modeling hurricanes Erin (2001) and Dennis (2005) are chosen and held constant during a series of microphysical sensitivity experiments for each storm. These are specifically designed to isolate the individual effects of altering one microphysical parameter at a time on the hurricane's intensity forecast and are carried out in a doubly or triply nested way. The initial and boundary conditions used in the innermost grid with finer resolution are obtained from the respective outermost grids where rain rate initialization is invoked. All of the results are illustrated for the highest-resolution innermost domain, which is integrated using an explicit microphysics scheme. Each of these experiments are integrated for a forty-eight hour forecast period, adequately capturing the mature and intensification stages of the two hurricanes. Skill scores are obtained from the results of the two sets of experiments. Root Mean Square Errors (RMSE) and Anomaly Correlations (AC) are computed by comparing the model output of each experiment to NCEP's final analysis (fnl) available at one-degree horizontal resolution and six-hour temporal resolution interpolated to the respective model grid. Taking into account the way that each experiment performs in terms of simulated storm intensity as well as optimized RMSE and AC, the optimal combination of microphysical processes (i.e. melting, evaporation, fall speed of hydrometeors) for each storm is determined. Then a final forty-eight hour forecast of each hurricane is made utilizing this optimal microphysical parameterization combination. The results from each final run are compared to observations, skill scores are computed, and the final intensity improvements for both hurricanes Erin and Dennis are shown. The results of this study strengthen the evidence that RRI and proper microphysical parameterization in mesoscale hurricane modeling are both useful and effective techniques, and combine to improve hurricane intensity forecasting in a mesoscale model.
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Date Issued: 2007
Identifier: FSU_migr_etd-0156
Format: Thesis

Title: Dissipation of Mesoscale Energy by Vortex-Topography Interaction.
Creator: Bishnu, Siddhartha, Dewar, William K., Chassignet, Eric P., Clarke, Allan J., Kopriva, David A., Florida State University, College of Arts and Sciences, Department of Earth,...
Show moreBishnu, Siddhartha, Dewar, William K., Chassignet, Eric P., Clarke, Allan J., Kopriva, David A., Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: Energy is introduced into the oceans primarily at large scales by means of wind, tides and surface buoyancy forcing. This energy is transferred to the smaller mesoscale eld through the geostrophic instability processes. The mesoscale eld appears not to have accelerated appreciably over the last several decades, so we can assume that the mesoscale loses energy at roughly the same rate it receives energy. Interestingly, how the mesoscale loses energy is not quite clear. We have been exploring...
Show moreEnergy is introduced into the oceans primarily at large scales by means of wind, tides and surface buoyancy forcing. This energy is transferred to the smaller mesoscale eld through the geostrophic instability processes. The mesoscale eld appears not to have accelerated appreciably over the last several decades, so we can assume that the mesoscale loses energy at roughly the same rate it receives energy. Interestingly, how the mesoscale loses energy is not quite clear. We have been exploring topographic interaction as a pathway by which the mesoscale may lose energy to unbalanced forward cascading flows. To demonstrate this phenomenon, an approximate model theory is developed which consists of solving a reduced set of the momentum equations in density coordinates for any topographic conguration. The equations are solved using a high order spectral element technique and the results are similar to already published MITgcm simulations.
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Date Issued: 2017
Identifier: FSU_FALL2017_Bishnu_fsu_0071N_14263
Format: Thesis

Title: Local Cooling Despite Global Warming.
Creator: Girihagama, Lakshika Nilmini Kumari, Nof, Doron, Tam, Christopher K. W., Bourassa, Mark Allan, Clarke, Allan J., Sura, Philip, Ewald, Brian D., Florida State University, College...
Show moreGirihagama, Lakshika Nilmini Kumari, Nof, Doron, Tam, Christopher K. W., Bourassa, Mark Allan, Clarke, Allan J., Sura, Philip, Ewald, Brian D., Florida State University, College of Arts and Sciences, Program in Geophysical Fluid Dynamics
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Abstract/Description: How much warmer is the ocean surface than the atmosphere directly above it? Part 1 of the present study offers a means to quantify this temperature difference using a nonlinear one-dimensional global energy balance coupled ocean–atmosphere model ("Aqua Planet"). The significance of our model, which is of intermediate complexity, is its ability to obtain an analytical solution for the global average temperatures. Preliminary results show that, for the present climate, global mean ocean...
Show moreHow much warmer is the ocean surface than the atmosphere directly above it? Part 1 of the present study offers a means to quantify this temperature difference using a nonlinear one-dimensional global energy balance coupled ocean–atmosphere model ("Aqua Planet"). The significance of our model, which is of intermediate complexity, is its ability to obtain an analytical solution for the global average temperatures. Preliminary results show that, for the present climate, global mean ocean temperature is 291.1 K whereas surface atmospheric temperature is 287.4 K. Thus, the surface ocean is 3.7 K warmer than the atmosphere above it. Temporal perturbation of the global mean solution obtained for "Aqua Planet" showed a stable system. Oscillation amplitude of the atmospheric temperature anomaly is greater in magnitude to those found in the ocean. There is a phase shift (a lag in the ocean), which is caused by oceanic thermal inertia. Climate feedbacks due to selected climate parameters such as incoming radiation, cloud cover, and CO2 are discussed. Warming obtained with our model compares with Intergovernmental Panel on Climate Change's (IPCC) estimations. Application of our model to local regions illuminates the importance of evaporative cooling in determining derived air-sea temperature offsets, where an increase in the latter increases the systems overall sensitivity to evaporative cooling. In part 2, we wish to answer the fairly complicated question of whether global warming and an increased freshwater flux cause Northern Hemispheric warming or cooling. Starting from the assumption of the ocean as the primary source of variability in the Northern hemispheric ocean–atmosphere coupled system, we employed a simple non–linear one–dimensional coupled ocean–atmosphere model similar to the "Aqua Planet" model but with additional advective heat transports. The simplicity of this model allows us to analytically predict the evolution of many dynamical variables of interest such as, the strength of the Atlantic Meridional overturning circulation (AMOC), temperatures of the ocean and atmosphere, mass transports, salinity, and ocean–atmosphere heat fluxes. Model results show that a reduced AMOC transport due to an increased freshwater flux causes cooling in both the atmosphere and ocean in the North Atlantic (NA) deep–water formation region. Cooling in both the ocean and atmosphere can cause a reduction of the ocean–atmosphere temperature difference, which in turn reduces heat fluxes in both the ocean and atmosphere. For present day climate parameters, the calculated critical freshwater flux needed to arrest AMOC is 0.14 Sv. Assuming a constant atmospheric zonal flow, there is both minimal reduction in the AMOC strength, as well as minimal warming of the ocean and atmosphere. This model provides a conceptual framework for a dynamically sound response of the ocean and atmosphere to AMOC variability as a function of increased freshwater flux. The results are qualitatively consistent with numerous realistic coupled numerical models of varying complexity.
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Date Issued: 2015
Identifier: FSU_2015fall_Girihagama_fsu_0071E_12927
Format: Thesis

Title: Characterization of Paleozoic Terranes and Terrane Accretion at the Southeastern Margin of Laurentia: Georgia and Alabama Appalachians.
Creator: Holm-Denoma, Christopher Scott, Tull, James F., Froelich, Philip, Odom, A. Leroy, Kish, Stephen A., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: The Paleozoic growth of the eastern margin of the North American continent is exemplified by the amalgamation of a series of terranes due to the closure of intervening ocean(s) and the obduction of fragments of oceanic and continental crust. The Appalachian orogen has traditionally been described as a culmination of three distinct events including the Taconic, Acadian, and Alleghanian orogenies. While evidence of the aforementioned discrete events has been well documented in the Appalachians...
Show moreThe Paleozoic growth of the eastern margin of the North American continent is exemplified by the amalgamation of a series of terranes due to the closure of intervening ocean(s) and the obduction of fragments of oceanic and continental crust. The Appalachian orogen has traditionally been described as a culmination of three distinct events including the Taconic, Acadian, and Alleghanian orogenies. While evidence of the aforementioned discrete events has been well documented in the Appalachians in general, substantiation of the effects and timing of each orogeny appears to be more ambiguous regionally, likely requiring differing tectonic models along strike of the orogenic belt. The response of Laurentia to orogenesis is important in determining the timing and extent of Paleozoic accretionary events as well as characterizing the accreted terranes themselves. Tectonic models of classically studied mountain belts including the Alps, Himalayas, and Appalachians were constructed relying heavily on identifying collisional structures formed during closure of an intervening ocean(s). The modern Pacific margin represents an alternative to collisional models termed accretionary orogenesis. Accretionary orogenesis is also variable in that there may be an advancing subduction boundary or a retreating subduction boundary (extensional accretionary orogen). This study examines the role of crustal growth in an accretionary margin along the southeastern margin of Laurentia during a time of extensive (orogen-wide) arc accretion and closure of an intervening ocean commonly associated with the Ordovician-aged Taconic orogeny. Structural, stratigraphic, geochemical and isotopic evidence suggest that the southeastern margin of Laurentia (Alabama promontory) remained open to an ocean (as an accretionary orogen) until at least the Acadian and possibly as late as the Alleghanian orogeny. The structural architecture of the terrane-bounding fault (Allatoona and Hollins-Line faults) systems and adjacent terranes and petrogenesis of arc-related volcanics and plutonic bodies provides insight into the early Paleozoic evolution of the southeastern margin of Laurentia.
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Date Issued: 2006
Identifier: FSU_migr_etd-3967
Format: Set of related objects

Title: Time Synchronized Sonification of Paleoclimatic Data: Orbital Eccentricity, Ecological Abundance and Stable Isotopes.
Creator: Goddard, Jay Daniel, Parker, William, Odom, Leroy, Wang, Yang, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: Paleoclimatic data including orbital eccentricity, mollusk species counts and carbonate isotope data are combined in an event based, time synchronized, parameter mapped sonification that plays backwards through geologic time from ~3.2 million years ago to ~7.4 million years ago. Interpretations of the sonified data are compared to the interpretations of previously published studies and insight has been gained regarding the usefulness of auditory display methods in this scientific context. The...
Show morePaleoclimatic data including orbital eccentricity, mollusk species counts and carbonate isotope data are combined in an event based, time synchronized, parameter mapped sonification that plays backwards through geologic time from ~3.2 million years ago to ~7.4 million years ago. Interpretations of the sonified data are compared to the interpretations of previously published studies and insight has been gained regarding the usefulness of auditory display methods in this scientific context. The field of auditory display has grown exponentially in recent years but there is a lack of papers that use sonification to explore science-based data within a legitimate scientific framework. The end result allow users to monitor a substantial portion of the Late Neogene period (around 4.2 million years in length) in less than 2 minutes. Users perceive shifts in mollusk counts (a temperature proxy) as the pink noise changes structure and travels L and R in the sound field. Low frequency discrete tones mimic the changing eccentricity of Earth's orbit as bell tones (representing isotope trends) move chaotically in the center channel. It is shown that sonification can preserve both simple and advanced structures in scientific data as shown in numerous sound examples and verified with unique figures that compare sonification waveforms or spectrograms to original publication figures.
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Date Issued: 2014
Identifier: FSU_migr_etd-8791
Format: Set of related objects

Title: Characterization of Metal-Reducing Microbial Communities from Acidic Subsurface Sediments Contaminated with Uranium(VI).
Creator: Edwards, Ellen Mclain, Kostka, Joel E., Balkwill, David, Krumholz, Lee R., Burnett, Bill, Chanton, Jeff, Department of Earth, Ocean and Atmospheric Sciences, Florida State...
Show moreEdwards, Ellen Mclain, Kostka, Joel E., Balkwill, David, Krumholz, Lee R., Burnett, Bill, Chanton, Jeff, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: Extraction and processing of uranium ore during the Cold-War era have left many sites around the world contaminated with uranium. Leaching of uranium into the groundwater is of major concern because oxidized uranium, U(VI), is toxic, soluble, and therefore mobile in subsurface environments where the majority of contamination resides. Uranium [U(VI)] can be immobilized from water by its reduction from UO22+ to insoluble U(IV) oxide, and biostimulation by the addition of carbon substrates has...
Show moreExtraction and processing of uranium ore during the Cold-War era have left many sites around the world contaminated with uranium. Leaching of uranium into the groundwater is of major concern because oxidized uranium, U(VI), is toxic, soluble, and therefore mobile in subsurface environments where the majority of contamination resides. Uranium [U(VI)] can be immobilized from water by its reduction from UO22+ to insoluble U(IV) oxide, and biostimulation by the addition of carbon substrates has been shown to stimulate the microbial reduction of U(VI) in contaminated subsurface environments. However, in order to develop effective bioremediation strategies for contaminant metals, the microbial communities and mechanisms controlling metal reduction need to be better understood, especially in acidic subsurface environments. This dissertation research used an array of microbiological and geochemical techniques to examine metal reduction in materials from the U.S. Department of Energy (DOE) Natural and Accelerated Bioremediation Research (NABIR)'s Field Research Center (FRC), in Oak Ridge, Tennessee, where subsurface sediments are cocontaminated with high levels of U(VI) and nitrate. The combination of low pH and high concentrations of nitrate and radionuclides in an aerobic subsurface environment is representative of many sites within the U.S. nuclear weapons complex managed by the DOE. Thus, results are not only important for bioremediation research at the FRC but can also be applied to other sites. Iron(III)-reducing bacteria (FeRB) have been demonstrated to rapidly catalyze U(VI) reduction and Fe(III) is an abundant electron acceptor in uranium-contaminated subsurface sediments. Thus, FeRB communities were the focus of this dissertation. The abundance, diversity, and activity of indigenous metal-reducing microbial communities likely to contribute to uranium reduction was examined in the field and under more controlled conditions in the laboratory. In chapter one, a combination of cultivation-dependent and cultivation-independent microbiological techniques were utilized to characterize metal-reducing bacteria in FRC subsurface sediments. Iron(III)-reducing enrichment cultures were initiated from pristine and contaminated (high in uranium, nitrate; low pH) subsurface sediments at pH 7 and pH (4-5). In selected enrichments, nitrate contamination was removed from the sediment by washing. Using a most probable number (MPN) approach and a range of different carbon sources (glycerol, acetate, lactate, or glucose), sediments of lower pH typically yielded lower counts of FeRB except when glucose was utilized as an electron donor in acidic enrichments. Phylogenetic analysis of the 16S rRNA gene sequences extracted from the highest positive MPN dilutions revealed that the predominant members of Fe(III)-reducing consortia cultured from pristine background sediments were closely related to the family Geobacteraceae, whereas a recently characterized Fe(III)-reducer (Anaeromyxobacter) and organisms not previously shown to reduce Fe(III) (Paenibacillus, Brevibacillus) predominated the Fe(III)-reducing consortia of contaminated sediments. Analysis of enrichment cultures using terminal restriction fragment length polymorphism (T-RFLP) strongly supported the cloning and sequencing results. Enrichment cultures of Fe(III)-reducers from contaminated sites were also shown to rapidly reduce millimolar amounts of U(VI) in comparison to killed controls. Using DNA extracted directly from the subsurface sediments, quantitative analysis of 16S rRNA gene sequences with MPN-PCR indicated that Geobacteraceae sequences were one to two orders of magnitude less abundant in contaminated as compared to pristine environments. In contrast, Anaeromyxobacter sequences were more abundant in contaminated sediments. Thus, results from a combination of cultivation-based and cultivation-independent approaches indicate that the abundance/ community composition of Fe(III)-reducing consortia in subsurface sediments is dependent upon geochemical parameters (pH, nitrate concentration) and microorganisms capable of producing spores (gram positives) or spore-like bodies (Anaeromyxobacter) were representative of acidic subsurface environments. In chapter two, microbial communities were studied in sediment microcosms under near in situ conditions in order to establish rates of respiration and to assess which environmental parameters might be governing activity. Rates of nitrate reduction, metal reduction, and electron donor utilization were measured in acidic subsurface sediments across a range of environmental variables (pH, nitrate) relevant to bioremediation. Microbial activity was minimal at pH 5 or below and in the absence of added electron donor, indicating that acidity is a master variable controlling microbial metabolism in FRC sediments, while high nitrate concentrations were not found to be toxic to microorganisms. In microcosms of neutral pH sediment and neutralized acidic sediment, similar, rapid rates of terminal-electron-accepting pathways were observed. The pathways of nitrate reduction were dictated by sediment pH, as denitrification predominated in glucose-amended sediments originating from neutral pH zones, whereas in neutralized acidic microcosms, metabolism shifted to dissimilatory nitrate reduction (to ammonium). Electron donors were determined to stimulate microbial metabolism leading to metal reduction in the following order: glucose > ethanol > lactate > hydrogen. A mass balance of carbon equivalents was obtained in glucose- and ethanol-amended microcosms. In neutralized acidic sediments amended with glucose, 50 to 60 % of carbon equivalents were recovered as fermentation products (mainly as acetate) and glucose-amended microcosms showed the highest iron reduction activity, while the extended presence of ethanol seemed to hinder iron reduction. The presence of bicarbonate greatly increased both nitrate and iron reduction activity in glucose-amended microcosms, more so than raising the pH by washing. Washing did increase iron reduction in glucose-amended microcosms as compared to neutralized acidic sediments, indicating that soluble toxins may somehow decrease iron reduction potential. ethanol > lactate > hydrogen. A mass balance of carbon equivalents was obtained in glucose- and ethanol-amended microcosms. In neutralized acidic sediments amended with glucose, 50 to 60 % of carbon equivalents were recovered as fermentation products (mainly as acetate) and glucose-amended microcosms showed the highest iron reduction activity, while the extended presence of ethanol seemed to hinder iron reduction. The presence of bicarbonate greatly increased both nitrate and iron reduction activity in glucose-amended microcosms, more so than raising the pH by washing. Washing did increase iron reduction in glucose-amended microcosms as compared to neutralized acidic sediments, indicating that soluble toxins may somehow decrease iron reduction potential. lactate > hydrogen. A mass balance of carbon equivalents was obtained in glucose- and ethanol-amended microcosms. In neutralized acidic sediments amended with glucose, 50 to 60 % of carbon equivalents were recovered as fermentation products (mainly as acetate) and glucose-amended microcosms showed the highest iron reduction activity, while the extended presence of ethanol seemed to hinder iron reduction. The presence of bicarbonate greatly increased both nitrate and iron reduction activity in glucose-amended microcosms, more so than raising the pH by washing. Washing did increase iron reduction in glucose-amended microcosms as compared to neutralized acidic sediments, indicating that soluble toxins may somehow decrease iron reduction potential. hydrogen. A mass balance of carbon equivalents was obtained in glucose- and ethanol-amended microcosms. In neutralized acidic sediments amended with glucose, 50 to 60 % of carbon equivalents were recovered as fermentation products (mainly as acetate) and glucose-amended microcosms showed the highest iron reduction activity, while the extended presence of ethanol seemed to hinder iron reduction. The presence of bicarbonate greatly increased both nitrate and iron reduction activity in glucose-amended microcosms, more so than raising the pH by washing. Washing did increase iron reduction in glucose-amended microcosms as compared to neutralized acidic sediments, indicating that soluble toxins may somehow decrease iron reduction potential. For the first time, rates of metal reduction and electron donor utilization were measured in acidic subsurface sediments across a range of environmental variables (pH, nitrate) relevant to bioremediation. In concurrence with previous studies of neutrophilic uranium-contaminated subsurface environments, metal reduction in the acidic subsurface did not occur until after nitrate was depleted to low levels in response to pH neutralization and carbon substrate addition. Through quantification of the rates and pathways of terminal-electron-accepting pathways in acidic subsurface sediments, we provide important inputs for reaction-based biogeochemical models that will greatly aid in the development of in situ radionuclide remediation strategies. In chapter 3, a pure culture of Fe(III)-reducing bacteria isolated from the FRC subsurface was further examined for its ability to reduce U(VI). Uranium measurements were conducted using a Kinetic Phosphorescence Analyzer, which was cross-calibrated using alpha spectrometry. The uranium reduction ability of isolate FRC32, was compared to a known uranium-reducing organism, Geobacter metallireducens. FRC32 was tested under various cultivation conditions, including a range of uranium and cell concentrations and up to 90% of 0.1-5 mM uranium was reduced. However, reduction in killed-control cultures suggests either a strong potential for abiotic reduction or the ability to form spores. Thus, the potential for uranium reduction was observed, but further research is necessary to determine which environmental parameters are controlling uranium transformation by this organism.
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Date Issued: 2005
Identifier: FSU_migr_etd-0599
Format: Thesis

Title: Development of New Techniques for Assimilating Satellite Altimetry Data into Ocean Models.
Creator: Yu, Peng, O'Brien, James J., Zou, Xiaolei, Dewar, William K., Clarke, Allan J., Iverson, Richard, Department of Earth, Ocean and Atmospheric Sciences, Florida State University
Abstract/Description: State of the art fully three-dimensional ocean models are very computationally expensive and their adjoints are even more resource intensive. However, many features of interest are approximated by the first baroclinic mode over much of the ocean, especially in the lower and mid latitude regions. Based on this dynamical feature, a new type of data assimilation scheme to assimilate sea surface height (SSH) data, a reduced-space adjoint technique, is developed and implemented with a three...
Show moreState of the art fully three-dimensional ocean models are very computationally expensive and their adjoints are even more resource intensive. However, many features of interest are approximated by the first baroclinic mode over much of the ocean, especially in the lower and mid latitude regions. Based on this dynamical feature, a new type of data assimilation scheme to assimilate sea surface height (SSH) data, a reduced-space adjoint technique, is developed and implemented with a three-dimensional model using vertical normal mode decomposition. The technique is tested with the Navy Coastal Ocean Model (NCOM) configured to simulate the Gulf of Mexico. The assimilation procedure works by minimizing the cost function, which generalizes the misfit between the observations and their counterpart model variables. The "forward" model is integrated for the period during which the data are assimilated. Vertical normal mode decomposition retrieves the first baroclinic mode, and the data misfit between the model outputs and observations is calculated. Adjoint equations based on a one-active-layer reduced gravity model, which approximates the first baroclinic mode, are integrated backward in time to get the gradient of the cost function with respect to the control variables (velocity and SSH of the first baroclinic mode). The gradient is input to an optimization algorithm (the limited memory Broyden-Fletcher-Goldfarb-Shanno (BFGS) method is used for the cases presented here) to determine the new first baroclinic mode velocity and SSH fields, which are used to update the forward model variables at the initial time. Two main issues in the area of ocean data assimilation are addressed: 1. How can information provided only at the sea surface be transferred dynamically into deep layers? 2. How can information provided only locally, in limited oceanic regions, be horizontally transferred to ocean areas far away from the data-dense regions, but dynamically connected to it? The first problem is solved by the use of vertical normal mode decomposition, through which the vertical dependence of model variables is obtained. Analyses show that the first baroclinic mode SSH represents the full SSH field very closely in the model test domain, with a correlation of 93% in one of the experiments. One common way to solve the second issue is to lengthen the assimilation window in order to allow the dynamic model to propagate information to the data-sparse regions. However, this dramatically increases the computational cost, since many oceanic features move very slowly. An alternative solution to this is developed using a mapping method based on complex empirical orthogonal functions (EOF), which utilizes data from a much longer period than the assimilation cycle and deals with the information in space and time simultaneously. This method is applied to map satellite altimeter data from the ground track observation locations and times onto a regular spatial and temporal grid. Three different experiments are designed for testing the assimilation technique: two experiments assimilate SSH data produced from a model run to evaluate the method, and in the last experiment the technique is applied to TOPEX/Poseidon and Jason-1 altimeter data. The assimilation procedure converges in all experiments and reduces the error in the model fields. Since the adjoint, or "backward", model is two-dimensional, the method is much more computationally efficient than if it were to use a fully three-dimensional backward model.
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Date Issued: 2006
Identifier: FSU_migr_etd-0789
Format: Thesis

Title: Using Chemical Tracers to Evaluate Feeding Habits in Coastal Marine Ecosystems: Stable Isotopes and Organic Contaminants.
Creator: Wilson, Rachel Marie, Chanton, Jeffrey P., Cooper, William T., Nowacek, Douglas P., Kucklick, John R., Wang, Yang, Burnett, William C., Department of Earth, Ocean and...
Show moreWilson, Rachel Marie, Chanton, Jeffrey P., Cooper, William T., Nowacek, Douglas P., Kucklick, John R., Wang, Yang, Burnett, William C., Department of Earth, Ocean and Atmospheric Sciences, Florida State University
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Abstract/Description: The use of chemical tracers to understand ecosystem interactions in the marine environment has gained increasing popularity over the past three decades. Carbon isotope abundances in organic matter sources in the marine system vary significantly making them a useful tracer for discriminating among such sources. Once taken up by primary producers, carbon isotope abundances are conservative throughout the food web. This allows us to measure carbon isotope abundances in secondary (and above)...
Show moreThe use of chemical tracers to understand ecosystem interactions in the marine environment has gained increasing popularity over the past three decades. Carbon isotope abundances in organic matter sources in the marine system vary significantly making them a useful tracer for discriminating among such sources. Once taken up by primary producers, carbon isotope abundances are conservative throughout the food web. This allows us to measure carbon isotope abundances in secondary (and above) consumers and infer organic matter source utilization in the system. Nitrogen isotope abundances, unlike carbon, are not conservative throughout the food web. However, they do fractionate predictably providing a tool by which to measure trophic level of consumer species. Sulfur isotopes, like carbon, differ among sources and are also conservative within the food web providing an additional tracer with which to estimate source contributions. However, concerns about the "dirtiness" of sulfur for analysis purposes put sulfur on the back burner as an ecosystem tracer. With recent improvements in technology and the need for multiple tracers in multi-source systems, sulfur isotope abundance measurements have experienced a resurgence. In this manuscript we use sulfur isotope abundances as a second tracer (with carbon isotope abundances) to estimate organic matter source utilization by consumers in a variety of habitats along the Florida Big Bend coastline. We begin our isotopic analysis of consumers in a Northwest Gulf of Mexico, freshwater dominated estuarine system, Apalachicola Bay, Florida (USA). In Chapter II we evaluate isotopic variation with body size to determine the smallest trophic unit in our system. In Chapter III we develop a concentration-corrected, dual-isotope, multi-source evaluation of organic matter utilization incorporating sulfur as a secondary tracer. We then go on to apply the results of this model to determine trophic level of consumers in Apalachicola Bay based on nitrogen isotope abundance data. In Chapter IV we demonstrate how isotopic variation of sources within a system can confound our interpretations of trophic structure using these methods. We further demonstrate that, in addition to isotopic variation, source inputs and availability may also vary within a given system. This makes comparison among sites more difficult and highlights the need to evaluate isotopic variation in individual systems prior to making comparisons or widespread generalizations about interactions. In Chapter V we apply these methods to a coastal seagrass community. We evaluate isotopic abundances in sources in consumers from the site. Then we apply the mixing model we develop in Chapter II to determine organic matter source utilization by consumers. Finally, we evaluate trophic level of individual consumers and trophic structure of the system based on nitrogen isotopic abundances. We demonstrate that source isotopic abundances differ from those same sources in the freshwater estuarine habitats. We also show that, while benthic organic matter was an important source in Apalachicola Bay, epiphytes provide the major organic matter source supporting consumers in the seagrass habitat. We use source utilization information and trophic level to assign consumers to trophic guilds in this system. The variety of organic matter source utilization is thought to contribute to the high levels of productivity found in this region. In addition to natural tracers, such as isotope abundances, we have also used organic pollutants as tracers of habitat utilization in the Florida Big Bend region. Organic contaminants found in coastal waters include compounds such as DDTs, PCBs, and chlordanes. Although no longer produced in the U.S., their historically wide-spread use and resistance to degradation contributes to their persistence in marine biota. We present data on chemical concentrations and congener profiles in bottlenose dolphins (Tursiops truncatus) and two abundant fish species from this region in Chapter VI. Although this area has been called "pristine" by previous researchers, we demonstrate the relativeness of this term, revealing that even the "forgotten coast" has been influenced by these ubiquitous contaminants. We use these compounds as tracers to evaluate bottlenose dolphin habitat utilization patterns in Florida Big Bend coastal waters. We found that the dolphins we sampled have differences in concentrations and patterns of contaminant loading indicating preference for feeding in specific areas and bays. Our results agree with suggestions based on sighting information that animals from the east and west regions of our study site rarely comingle and that even in the western site, individual animals express preferences for either St Joseph or St Andrews Bay foraging grounds.
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Date Issued: 2010
Identifier: FSU_migr_etd-0901
Format: Thesis

Title: Investigation of the Impacts of Greenland Ice Sheet Melting on the along-Shelf Flow on Greenland Shelves and the Labrador Sea Deep Convection.
Creator: Sangmanee, Chalermrat, Clarke, Allan J., Tam, Christopher K. W., Knapp, Angela N., Bourassa, Mark Allan, Dewar, William K., Florida State University, College of Arts and...
Show moreSangmanee, Chalermrat, Clarke, Allan J., Tam, Christopher K. W., Knapp, Angela N., Bourassa, Mark Allan, Dewar, William K., Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science
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Abstract/Description: Gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite measuring system show that Greenland is losing mass as water is lost to the ocean. Past work has suggested that the freshwater flux from Greenland, particularly along the southeastern coast, may be affecting the Labrador Sea deep convection, a major driver of the world deep ocean circulation. The main objectives of this thesis are to examine (1) the relationship between Greenland freshwater flux and the...
Show moreGravity measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite measuring system show that Greenland is losing mass as water is lost to the ocean. Past work has suggested that the freshwater flux from Greenland, particularly along the southeastern coast, may be affecting the Labrador Sea deep convection, a major driver of the world deep ocean circulation. The main objectives of this thesis are to examine (1) the relationship between Greenland freshwater flux and the near-surface Labrador Sea salinity; (2) the response of the Greenland shelf water flow to the freshwater flux from the coast; and (3) to predict when the Labrador Sea deep convection will shut down because of the near-surface Labrador Sea freshening. Using the GRACE results and analysis of Argo float hydrographic data showed that there is a strong correlation between the anomalous annual freshwater flux onto the southeastern Greenland shelf and the freshening of the Labrador Sea several months later. The corresponding regression coefficient is physically reasonable and the delay in freshening is what you would expect based on eddy propagation from the west Greenland coast to the site of Labrador Sea deep convection. Satellite altimeter data was used to estimate the interannual shelf water flow, but the flow trend was too small to be determined. Calculations of the heat flux during winter in the Labrador Sea region of deep convection showed that if the freshening continues at the present rate, in about 31 years the cooling heat flux in water will not be able to overcome the freshwater near-surface buoyancy and deep convection will cease.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Sangmanee_fsu_0071E_13961_P
Format: Set of related objects

Theses and Dissertations (266)	+ -
Center for Ocean-Atmospheric Prediction Studies (22)	+ -
Undergraduate Honors Theses (9)	+ -
Department of Earth, Ocean and Atmospheric Science (1)	+ -
Digitized Theses and Dissertations (1)	+ -

Atmospheric sciences (259)	+ -
Meteorology (150)	+ -
Earth sciences (119)	+ -
Geophysics (110)	+ -
Atmospheric physics (3)	+ -

Climatic changes (2)	+ -
Ecology (2)	+ -
Evolution (Biology) (2)	+ -
Benthos (1)	+ -
Environmental sciences (1)	+ -
Fresh water (1)	+ -
Geography (1)	+ -
Interstitial animals (1)	+ -
Mathematics (1)	+ -
Soil moisture (1)	+ -

text (298)	+ -
doctoral thesis (5)	+ -
master thesis (2)	+ -

Florida State University (266)	+ -
Department of Earth, Ocean and Atmospheric Sciences (252)	+ -
Hart, Robert (39)	+ -
Liu, Guosheng (39)	+ -
Huettel, Markus (28)	+ -

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