The Tongue of the Ocean (TOTO) region located within the Bahamas archipelago is a relatively under-studied region in terms of both its biological and physical oceanographic characteristics. This region is comprised of a deep trough along with steep boundaries that are commonly associated with elevated turbulent dissipation rates, and #949;, when impacted by currents and internal waves. A prey-field mapping cruise took place in the fall between 9/15/2008 and 10/01/2008, consisting of a series of transects and 'clovers' to study the spatial and temporal variability. The region is characterized by a deep scattering layer (DSL), which is preyed on by nekton that serves as the food for beaked whale and other whale species. This study marks the first of its kind where concurrent measurements of acoustic backscatter and turbulence have been conducted for a nekton scattering layer well below the euphotic zone. In this novel study, turbulence data collected from a deep microstructure profiler are compared to biological and shear data collected by a 38 kHz Simrad EK 60 echosounder and a hydrographic Doppler sonar system, respectively. From these measurements, the primary processes responsible for the turbulent production in the TOTO region are assessed. The DSL around 500 m and a surface scattering layer (SSL) are investigated for raised and #949; values. Strong correlation between turbulence levels and scattering intensity of prey is generally found in the SSL with dissipation levels as large as ~10-7 W kg-1, three orders of magnitude above background levels. In the deep scattering layer, however, the correlations are relatively weak, but exhibit dissipation levels ~10-8 W kg-1. The absence of turbulence bursts of O(10-5 W kg-1) proposed to occur within dense biomass aggregations suggests biologically generated turbulence is not efficient by the marine biosphere. Areas of elevated turbulence have many implications from sustaining the abyssal stratification to transporting of nutrients and gases to and from the surface. We present an examination of the TOTO mixing levels with those from a typical open ocean site. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2011. / March 31, 2011. / Includes bibliographical references. / William Dewar, Professor Directing Thesis; Louis St. Laurent, Committee Member; Carol Anne Clayson, Committee Member; Joel Kostka, Committee Member.

This study aims to unravel the driving factors of rainfall variability on interannual time-scales and for extreme events over western equatorial Africa (WEA). We first defined homogeneous and contiguous regions with respect to interannual rainfall variability, using different clustering techniques. The spatial patterns are seasonally dependent and demonstrate the remarkable heterogeneity of the region. They also are dissimilar to those based on the annual cycle, confirming the difference in their driving factors. Once regionalization was accomplished, we examined how global SST and SLP and well-established modes of variability are related to interannual rainfall variability. The relationships are seasonally and regionally dependent, and we found ocean sectors that detect such links better than the variability modes. That is more crucial when the correlations are evident three months in advance, and provide forecast potential. We then analyzed the driving factors of extreme rainfall events for four select cases. Three of those are the coastal regions. JFM, AMJ and OND are variously considered. The fourth case is the eastern WEA region during OND. The SST-rainfall links are in agreement with the interannual analysis. Moreover, while the extreme rainfall events are associated with the local ocean regions through the induced convective activity and static stability, they are modulated dynamically by remote forcing from the distant oceans via an atmospheric bridge. In addition, we suggest that the moisture availability does not determine the amount of rainfall, and the role of SST as a moisture provider is less important than as a modulator of vertical motion. However, the moisture flux divergence shows apparent contrast between wet and dry composites. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester, 2011. / June 2, 2011. / Includes bibliographical references. / Sharon E. Nicholson, Professor Directing Dissertation; Allan J. Clarke, University Representative; Jon E. Ahlquist, Committee Member; Guosheng Liu, Committee Member; Philip Sura, Committee Member.

The Gulf of Mexico is among the most populated of coastlines threatened by tropical cyclones and has experienced some of the most destructive hurricanes in history. The importance of the warm ocean waters of the Gulf in providing optimal conditions for tropical cyclone intensification is becoming more clear with recent research; thus, understanding factors that affect the upper ocean heat content in the Gulf is essential to anticipating hurricane intensity. In this study, two reanalysis data sets, NASA's Modern Era Retrospective-analysis for Research Applications (MERRA) and the NCEP Climate Forecast System Reanalysis (CFSR), are used to calculate the surface heat flux budget and the upper ocean heat budget of the Gulf for 29 winter seasons (November – March), since the greatest spatial and temporal variability in the surface fluxes occurs during this season. The results of the heat budget analysis indicate that the turbulent fluxes largely drive the magnitude and the interannual variability of the rate of oceanic heat storage. Marine cold-air outbreaks (CAOs) bring cold, dry polar air over the Gulf throughout the winter season, forcing the release of extreme latent and sensible heat fluxes from the ocean to the atmosphere. To understand the impact of these events on the interannual variability in the rate of oceanic heat storage, we create a climatology of CAO event characteristics for 29 winter seasons. We find that on average, over half of the total winter season flux loss occurs due to surface fluxes during CAO events, the duration of which only accounts for about 15% of the winter season. Therefore, capturing the heat flux loss due to these events is essential to accurately determining the rate of change in upper ocean heat content throughout the winter season, as well as during the ensuing months. The possible impact of this extreme winter season heat flux loss on the following hurricane season is explored on a preliminary basis through comparison of the interannual variability in the July average upper ocean heat content to that of the CAO heat flux loss. My results suggest that the heat flux loss due to CAOs does affect the variability of the summer season ocean heat content. However, this variability is very small in comparison to the total ocean heat content. More in depth analysis must be done to better determine how long-lasting the effects of the winter season heat flux loss are, and to assess their influence on the thermal structure of the upper ocean during the hurricane season. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2011. / June 1, 2011. / Upper Ocean Heat Content, Heat Budget, Climatology, Tropical Cyclone / Includes bibliographical references. / Carol Anne Clayson, Professor Directing Thesis; Robert Hart, Committee Member; Doron Nof, Committee Member.

Satellite observations have revealed a small-scale (< 1000 km) air-sea coupling in regions of strong sea surface temperature (SST) gradients (e.g., fronts, currents, eddies, and tropical instability waves), where the surface wind and wind stress are modified. Surface winds and wind stresses are persistently higher over the warm side of the SST front compared to the cool side, causing perturbations in the dynamically and thermodynamically curl and divergence fields. Capturing this small-scale SST-wind variability is important because it can significantly impact both local and remote (i.e., large scale) oceanic and atmospheric processes. The SST-wind relationship is not well represented in numerical weather prediction (NWP) and climate models, and the relative importance of the physical processes that are proposed to be responsible for this relationship is actively and vehemently debated. This study focuses on the physical mechanisms that are primarily responsible for the SST-induced changes in surface wind and wind stress, and on the physical implication on ocean forcing through Ekman pumping. The roles that SST-induced atmospheric baroclinicity and boundary-layer stability play in modifying the surface vector wind in regions of strong SST gradients are examined with an idealized model. Modeled changes in surface wind speed due to changes in atmospheric boundary-layer stability and baroclinicity are largely between -2.0 and 2.0 m s-1, which is consistent with past observational findings. The baroclinic-related changes in the surface vector wind are found to have a largely linear dependence on the SST gradient, whereas the stability-related changes are highly non-linear. The linearity of the baroclinic impacts matches that of the observed (satellite and in situ) SST-wind relationship. This result suggests that the baroclinic-related mechanism is the leading factor in driving the observed surface wind response to strong open ocean SST fronts on scales greater than 25 km. This study shows that the baroclinic-related changes in Ekman pumping are significant (first-order) over a seasonal (2003 winter season) time scale and that the small-scale impacts are quite important over larger spatial scales. These findings highlight the need to consider the small-scale SST-wind relationship even in coarser resolution model simulation, for which it may be feasible to parameterize because of the linear nature of the baroclinic-related effects. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester, 2014. / June 27, 2014. / Air-Sea Interaction, Sea Surface Temperature Gradients, SST-wind relationship, Surface Vector Winds / Includes bibliographical references. / Mark A. Bourassa, Professor Directing Dissertation; Eric Chassignet, University Representative; William Dewar, Committee Member; Guosheng Liu, Committee Member; Xiaolei Zou, Committee Member.

Initializing Coupled General Circulation Models (CGCMs) for routine seasonal ENSO prediction is currently an onerous task. This is one of the main reasons on why the CGCMs participating in the Coupled Model Intercomparison Project 5 (CMIP5), which represents the state-of-the-art in climate modeling, is infrequently used for routine seasonal prediction of El Niño and the Southern Oscillation (ENSO), the largest known natural variability that affects the global climate. In this work we propose a simple ocean initialization technique that can be adopted for any CGCM for seasonal predictability studies of ENSO. The technique entails finding the best analogues from a long historical simulation of the CGCM to the targeted air-ocean initial state. Since this study is on seasonal ENSO predictability, the metrics chosen to pick the analogues were confined to a set of 4 variables in the tropical Pacific that were found sensitive to the Niño3.4 SST variations. They were Tropical Pacific SSTs, thermocline depth, time tendency of thermocline depth, and the zonal wind stress. The multiobjective optimization technique was used to optimize the overall analogue match across the four variables giving equal weighting to each. This in effect uses the minimum root mean square difference between the targeted initial state and the model states to pick the analogue from the historical simulation of the CGCM that matched the targeted initial state. The chosen analogues were then perturbed using empirical singular vectors to provide additional initial conditions to generate in total 12 ensemble members per seasonal hindcast. The methodology for ocean initialization was first tested with the Cane-Zebiak model, a two layer reduced gravity ocean model coupled to a statistical atmosphere. We found that the methodology is sensitive to the length of the library generated from the historical simulation of the model and also on the fidelity of the model in simulating the ENSO. These toy model experiments also revealed the benefit of using a multi-variate metric to choose the analogues. Before proceeding to conduct the proposed work with a CGCM, the CMIP5 historical simulations for the 20th century were analyzed for their ENSO simulation. The mean-state and ENSO variations were analyzed in both the atmosphere and ocean. It was found that most of the CMIP5 models exhibit cold (warm) biases in the equatorial (subtropical eastern) Pacific Ocean sea surface temperature that are reminiscent of the split inter-tropical convergence zone phenomenon. There is, however, a major improvement in the representation of the power spectrum of the Niño3.4 sea surface temperature variations which shows that, as in the observations, a majority of the models display a spectral peak in the 2-7 year range, have a near linear relationship with the displacement of the equatorial thermocline and exhibit a robust atmospheric response to ENSO variations. Several issues remain in the CMIP5 simulations such as erroneous amplitudes in the Niño3.4 sea surface temperature spectrum's peak and a width of the spectral peak that is either too broad or too narrow. It is also seen that most CMIP5 models unlike the observations extend the ENSO variations in the equatorial Pacific too far westward beyond the dateline and there is very little asymmetry in event duration between the warm and cold phases. ENSO variability forces a dominant mode of rainfall variability in the southeastern United States, especially in the boreal winter season. The CMIP5 exhibited a wide range of response in this metric with several displaying weak to non-existent, some showing relatively strong, and one indicating excessively zonally-symmetric teleconnection over the southeastern United States. Based on this study we choose to use the CCSM4, which displayed a reasonable ENSO simulation for our experimental seasonal hindcasts with the proposed ocean initialization strategy. The seasonal hindcasts were initiated in beginning of March of each year from 1980-2012 follows from seeking a model state that minimizes the RMS difference in SST, zonal wind stress, thermocline depth and thermocline depth tendency from a 600 year continuous integration of the CCSM4 with the corresponding metric in the Global Ocean Data Assimilation (GODAS) of the National Centers for Environmental Prediction (NCEP). The four variables are jointly optimized by multi-objective optimization of the resulting root mean squared (RMS) difference curves, essentially minimizing the normalized RMS in all four parameters. Some of the main highlights of our results from the seasonal hindcasts are: i) The deterministic skill as measured by the anomaly correlation of the monthlyensemble mean and observed SST anomalies in the Niño3.4 region at 9-month lead is 0.71. ii) The probabilistic prediction of the Niño3.4 SST anomalies at 9-month lead for warm and cold ENSO events as measured by the area under the Relative Operating Characteristic Curve is 0.7 and 0.8 respectively. Likewise the brier skill score for warm and cold ENSO events at 9-month lead for Niño3.4 SST anomalies is 0.11 and 0.21 respectively. iii) The global teleconnection patterns in SST, precipitation and 500hPa geopotential heights with Niño3.4 SST variations in the seasonal hindcast in Oct-November-December season (7 month lead) is reasonable. From these results we demonstrate that the proposed initialization strategy is viable to deploy many other existing CMIP5 models for either operational seasonal ENSO prediction or ENSO predictability studies. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester, 2014. / April 1, 2014. / ENSO, Seasonal Forecasting / Includes bibliographical references. / Vasu Misra, Professor Directing Dissertation; Mike Burmester, University Representative; Eric P. Chassignet, Committee Member; Zhaohua Wu, Committee Member; Philip Sura, Committee Member.

<p>Increasing CO₂ concentrations in the Earth's atmosphere have led to global warming with climate change effects. Future RCP scenarios per the IPCC suggest that local solutions to limit emissions are necessary but may not suffice to combat the anthropogenic CO₂ problem. Climate intervention has been given increasing consideration. A climate intervention approach of removing CO₂ from the atmosphere through dry ice deposition and storage in Antarctica is considered. While the technology needs continued development, understanding the meteorological response to significant carbon dioxide removal (CDR) in Antarctica takes precedence. Various Antarctica CDR scenarios are simulated through the fully-coupled general circulation model CESM 2.1.1. Modern simulations (15 years) with prognostic CO₂ include 1) anthropogenic emissions (control), 2) no emissions, 3) emissions with ~4.5 ppmv sequestration annually (half sequestration), and 4) emissions with ~9 ppmv sequestration annually (full sequestration). Full sequestration attempts to remove enough CO₂ to achieve pre-industrial concentration by the end of the simulation. Experiments 1) and 3) were continued until mid-21st century (50 years total) with SSP1-2.6 conditions and emissions to examine the CDR impact on the atmosphere under the Paris Treaty Agreement scenario (which limits Earth's warming to 1.5^oC-2^oC above pre-industrial values). </p> <p> Modern simulations show sequestration scenarios have more of an impact on 2m-air temperature and little effect on precipitation patterns in 15 years. SSP1-2.6 simulations show that an additional 1^oC of warming can be inhibited by continuing sequestration and limiting emissions. Further, sequestration shows counteraction to warming in many of the locations that are predicted to warm per the RCP 2.6 scenario in the IPCC (2013), as well as counteraction to the predicted IPCC precipitation changes. These results are obtained from one simulation of each experiment, and it is recognized that ensemble runs in line with IPCC predictions are necessary to examine all possible predictions to CDR. Future considerations include sea level rise, carbon cycle response, convective parameters, and relocation of sequestration.<a></a></p>

ABSTRACT This work presents turbulence data collected in the Gulf of Mexico in an attempt to quantify the source or sources of turbulent dissipation along the continental shelf and any possible causes for its seasonal change. In addition, this work is an effort to assist those concerned with mixing and transport problems working in similar environments. Multiple offshore research cruises were held in both the Gulf of Mexico and the Atlantic Ocean for data collection. The basis of the work is a tethered profiler that measures dissipation-scale turbulence as well as temperature and conductivity at high-resolution. This data is compared against that collected by an in situ acoustic Doppler current profiler and wind meter along with salinity and conductivity measurements taken during the casts. The primary location for this study is a flat, featureless location in the northeastern portion of the Gulf known as Apalachee Bay in water of 20 meters depth. Because of the extremely gradual slope of the shelf in this region, this location is approximately 20 nautical miles off shore. Due to the tidal and wind variations in the area, along with the extreme seasonal temperature swings and surface freshwater flux, it has been found that a significant amount of turbulent energy is absorbed in this region. Density calculations indicate an abrupt seasonal overturning of the water column; cooling during the winter months creates a thermally homogeneous water column. What little stratification does exist, however, is subsequently overturned by a combination of the reversal of the along-isobath currents and increasing winds. Late summer profiles showed a well-mixed water column with very little remaining stratification. / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2012. / December 19, 2011. / boundary layer, dissipation, Gulf of Mexico, microstructure, turbulence / Includes bibliographical references. / Carol Anne Clayson, Professor Directing Thesis; Markus Huettel, Committee Member; Louis St. Laurent, Committee Member; Georges Weatherly, Committee Member.

This study examines the impact of anomalous differential generation of available potential energy by absorbing aerosols on the transition and early active phases of the south Asian summer monsoon. Aerosol direct and indirect effects represent radiative forcings which can modify tropospheric temperature profiles and extend cloud lifetimes. Recent studies have suggested that over monthly and seasonal time scales, these effects can lead to modified flow and rainfall regimes in the south Asian monsoon region. Of special interest is the covariance of heating and temperature prior to active monsoon onset. It can be shown that anomalous generation of available potential energy due to aerosol radiative effects can impact the cascade of energy from the Hadley circulation to the monsoon non-divergent flow. In order to quantify the potential impact of aerosol radiative forcing and the resulting changes in monsoon onset timing and intensity, an ensemble of WRF/CHEM regional weather and chemistry model forecasts are created for the south Asian summer monsoon region during May June and July. The forecasts with aerosol direct and indirect effects are compared to control forecasts without aerosols. The evolution of irrotational and non-divergent kinetic energy, generation of available potential energy and rainfall are presented. It is found that the ensemble with aerosol direct and indirect forcing contains on average a more intense and rainy onset over south India which is statistically significant compared to the ensemble variability. The more intense monsoon onset is related to a more intense Arabian Sea low level jet which is displaced to the south compared to the jet in forecasts without aerosol. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester, 2012. / June 13, 2012. / Includes bibliographical references. / T. N. Krishnamurti, Professor Co-Directing Dissertation; Paul Ruscher, Professor Co-Directing Dissertation; James Tull, University Representative; Robert Hart, Committee Member; Guosheng Liu, Committee Member.

The primary goal of this dissertation was to explore the use of stable isotope analysis as a tool to understand how energy flows at several layers of biological organization from the individual to the ecosystem level. With the exception of phosphorus, the primary elements that are utilized by living organisms on earth (H, C, N, O, & S) have at least one stable isotope. The isotopes of carbon, nitrogen, and sulfur are particularly useful for following the flow of energy within and between organisms, because these elements are the primary components in proteins, carbohydrates, and fats. When used in combination and when significant contrast in isotope values exists, stable isotopes can be used to elucidate biological processes from the intercellular to global scale. Chapter one will provide an introduction to the fundamentals of stable isotope analysis and a review of the state of its use in biological systems. In chapter two, the usefulness of stable isotope to identify diet changes in wild gag grouper is determined with a repeated-measures diet-shift experiment on four adult gag held in the laboratory. Fish were initially fed a diet of Atlantic mackerel, Scomber scombrus, (mean 13C = -21.3 / ± 0.2, n= 20) for a period of 56 days and then shifted to a diet of pinfish, Lagodon rhomboids, (mean 13C = -16.6 / ± 0.6, n= 20) for the 256 day experiment. I developed a non-lethal surgical procedure to obtain biopsies of the muscle, liver, and gonad tissue monthly from the same four fish. I then determined the 13C value of each tissue by isotope-ratio mass spectrometry. For the gonad tissue, I used the relationship between C/N and lipid content to correct for the influence of lipids on  13C value. I observed a significant shift in the 13C values of all of the tissues sampled in the study. Carbon turnover rates varied among the three tissues, but the shift in diet from mackerel to pinfish was clearly traceable through analysis of  13C values. The turnover rates for muscle tissue were 0.005 / day-1, and for gonad tissue was 0.009 / day-1. Although it is generally thought that tissue turnover rates in ectotherms are driven primarily by growth, I found that metabolic rate can be a major factor driving tissue turnover in adult gag. Chapter three explores the application of stable isotope analysis to trace the transfer of secondary production from temperate, coastal seagrass habitat to offshore reefs. Seagrass meadows are among the most productive ecosystems in the marine environment. It has been speculated that much of this production is exported to adjacent ecosystems via the movements of organisms. My study utilized stable isotopes to track seagrass derived production into offshore food webs in the northeastern Gulf of Mexico. I found that gag grouper (Myctereoperca microlepis) on reefs as far as 90 km from the seagrass beds incorporate a significant portion of seagrass derived biomass. The muscle tissue of gag grouper, a major fisheries species, was composed on average of 19% ±10% seagrass-habitat-derived biomass. The timing of this annual seagrass subsidy appears to be important in fueling gag grouper egg production. The 34S values of gag grouper gonad tissues varied seasonally and were34S depleted during the spawning season, indicating that gag utilize the seagrass derived biomass to support reproduction. If such large-scale trophic subsidies are typical of temperate seagrass systems, then loss of seagrass production or habitat would result in a direct loss of offshore fisheries productivity. After showing that a significant quantity of secondary production is transferred across ecosystem boundaries in chapter four, this flux is placed in the context of the flux of organic nitrogen, the primary limiting nutrient in the Gulf of Mexico. The migration of a single species, pinfish (Lagodon rhomboids), exports the equivalent of 2.85 x 107 ± 9.32 x 106 kg of primary nitrogen to the northeastern Gulf of Mexico. This flux is greater than the amount of primary nitrogen fluxed by the Apalachicola River and slightly less than the amount of organic nitrogen fluxed via atmospheric deposition and fixation by Trichodesmium. Although fish flux is less than 3 % of the total quantity of material fluxed to the offshore environment by mass, gag grouper biomass contains 19 ± 10 % seagrass derived-material. Stable carbon isotope values of otoliths can provide long-term records of the environmental conditions experienced by fish. However, as shown in chapter five because otoliths contain carbon from metabolic sources, it is necessary to determine the proportion of metabolically derived carbon to properly interpret otolith 13C values. To evaluate the relative influence of dietary carbon and ambient seawater dissolved inorganic carbon (DIC) on the 13C isotopic composition of fish otoliths, juvenile red drum (Sciaenops ocellatus) were raised for 6 and 9 months in tanks with flow-through ambient seawater and fed diets differing by 2.1 / (p < 0.001) in carbon isotope composition (13C). At the end of the experiment, muscle tissue from the two treatments reflected the isotopic composition of the diets and differed by 2.1 / (p <0.001). Muscle tissue from both groups was enriched by 1.5 / in 13C relative to the respective diets. The carbon isotope values of otoliths were enriched ~16-17 / relative to the respective diets, indicating that DIC was the dominant source (85%-92%) for otolith carbon relative to carbon derived from diet. However, otoliths from the two treatments differed by 1.6 / and expressed 60% of the difference in the isotope values of the diets. This result indicates that the nutritional characteristics of food may be a factor influencing the incorporation of metabolic carbon in the otolith. This is one of the first studies to provide evidence that the nutritional value of food influences otolith 13C value. / A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester, 2011. / September 2, 2011. / ecology, ecosystem connectivity, fishereis, gag, stable isotopes, trophic transfer / Includes bibliographical references. / Jeffery Chanton, Professor Directing Dissertation; Thomas Miller, University Representative; William Landing, Committee Member; David Thistle, Committee Member; Felicia Coleman, Committee Member.

Ocean Drilling Program Site 752 on Broken Ridge in the Indian Ocean recovered an expanded section containing Paleocene and lower Eocene calcareous nannofossils. Qualitative counts show a diverse, high-latitude assemblage of primarily moderately preserved and abundant nannofossils. The assemblage was deposited in the high southern latitudes before Broken Ridge rifted off of the Kerguelen Plateau in the middle Eocene. Minor modifications allowed Okada and Bukry's 1980 low-latitude zonation to be utilized at this site for Zones CP1a through CP10. Various markers such as the first occurrence of Discoaster diastypus and Tribrachiatus bramlettei, or the last occurrence of Fasciculithus sp., were used in past studies to determine the Paleocene/Eocene boundary. At this high-latitude site, both D. diastypus and T. bramlettei are rare or absent, so the last occurrence of Fasciculithus sp. was used to approximate the boundary. Ocean Drilling Program Site 758 cored the northern Ninety-East Ridge in the Indian Ocean. Ninety-East Ridge is a hotspot trace formed from the northward movement of the Indo-Australian Plate. This site contains a more condensed section in which much of the lower Paleocene and all of the lower Eocene are absent. A more generically diverse, but still high-latitude assemblage of nannofossils is examined in this study. First seen in Zone CP6, a large variety of Discoaster okadai is present at Site 758. Figures are presented to show the variation in morphology of this species in the Indian Ocean. Much research has been done to associate Paleogene nannofossil genera with different paleoceonographic conditions. Both Sites 752 and 758 show a shift from primarily small, cool-water, eutrophic species near the K/T boundary (such as Prinsius martinii, Prinsius dimorphosus, or Cruciplacolithus primus) to warm-water, oligotrophic species (such as Sphenolithus, Discoaster, or Zygrhablithus bijugatus). This trend is seen in Principal Component Analysis and is more obvious at Site 752 due to the presence of a complete lower Paleocene section and lower Eocene nannofossils. / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2012. / March 16, 2012. / Broken Ridge, Nannofossils, Nannoplankton, Ninety-East Ridge, ODP, PETM / Includes bibliographical references. / Sherwood Wise, Professor Directing Thesis; Yang Wang, Committee Member; William Parker, Committee Member.