This study evaluates the impacts of two different precipitation types on stage heights from a fully integrated and distributed, physically based hydrologic model - MIKE SHE. Simulations using a network of South Florida Water Management District (SFWMD) rain gauge measurements in the form of Thiessen polygons are compared with those using a &126; 4 x 4 km gridded historical precipitation database prepared at Florida State University (FSU). The FSU procedure employs a version of the National Weather Service (NWS) Multi-sensor Precipitation Estimator (MPE) algorithm. Each precipitation input is at both hourly and daily intervals. Simulated stages from MIKE SHE are evaluated over the relatively flat Big Cypress Basin (BCB) which has a maximum elevation range of &126; 12.5 m over a 1661 km&178; area. Daily averaged stage heights are analyzed at four stream gauge sites along canals within the BCB using seasonally based three-month model runs between 2003 to 2005 plus two separate case studies containing significant rainfall accumulations. Results show a high correlation between precipitation values of the FSU MPE database and the SFWMD rain gauges because the rain gauge data are incorporated into the MPE algorithm. Therefore, stage hydrographs and statistical properties of the stages generally are very similar between the two precipitation datasets at both temporal resolutions. Slightly greater differences are found between observed stages and those from the four versions of modeled output. The high resolution FSU MPE precipitation estimates generally provide improved stages compared to the SFWMD rain gauges. The use of hourly temporal resolution input impacts the timing and magnitude of the resulting stages. The modeled stages based on hourly precipitation values generally provide a faster hydrologic response and better simulate the observed stages than do daily values during extreme rainfall events (e.g., Hurricane Wilma). We believe that improved multi-sensor products and quality control procedures can be beneficial to enhancing water management decisions and flood forecasting within the SFWMD. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester, 2008. / November 6, 2008. / Precipitation Comparison, Watershed Management / Includes bibliographical references. / Henry E. Fuelberg, Professor Directing Thesis; Phillip Cunningham, Committee Member; Guosheng Liu, Committee Member; Chandra S. Pathak, Committee Member.

The abrupt temperature rise in the beginning of the Holocene is the most dramatic climatic change of the last 80,000 years. It is suggested here that the change is due to the abrupt opening of the Bering Strait which we hypothesize was initially jammed with icebergs, common during the termination of the last glaciation. Once sea-level rose beyond a critical point, the dam broke allowing low salinity water (which dominated the Atlantic during the Younger Dryas) to be flushed out of the Atlantic. This then, allowed the global wind field to force more Southern Ocean water into the Atlantic. A new analytical coupled ocean-atmosphere model was developed and applied to the North Atlantic, in an attempt to quantify the temperature change due to the opening and closing of the Bering Strait. Heat, salt and mass are all conserved within a box in the North Atlantic. A convection condition allows water to enter the deep layer, and the ocean and atmosphere are connected through their Ekman layers. Restarting convection, through the opening of the Bering Strait, increases mean oceanic and atmospheric temperatures by 2-4 ºC and 14-17 ºC, respectively. These values are favorably compared to those found in both the CEREGE alkenone and GISP II Greenland ice core records. The temporary damming/jamming of the Bering Strait due to large icebergs was examined using a simple laboratory box model. Results show the stability of the dam to be dependent on the rate of sea level rise, which at 1 cm yr -1, should be sufficiently slow to allow a temporary dam to exist for several thousands of years. Sea ice probably fused icebergs together, and through ridging could have created a 30-40 m vertical ice wall. / A Dissertation Submitted to the Department of Oceanography in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy. / Fall Semester, 2006. / July 21, 2006. / Deep-Water Formation, Meridional Overturning Cell, Heinrich Events, Temporary Daming, Climate Stability, Convection / Includes bibliographical references. / Doron Nof, Professor Directing Dissertation; Christopher Hunter, Outside Committee Member; William Burnett, Committee Member; Allan J. Clarke, Committee Member; Georges L. Weatherly, Committee Member; James J. O’Brien, Committee Member.

A medium complexity, nitrogen-based ecosystem model is developed in order to simulate the ecosystem in the northeast tropical Pacific. Several physical processes have major impact on the ecosystem in this region, most importantly intense wind jets along the coast and upwelling at the Costa Rica Dome (CRD). The ecosystem model is run "offline", using a realistic physical ocean model hindcast as input. The physical model is a subdomain of the global Navy Coastal Ocean Model, which is a hybrid sigma-z level model. The model assimilates Modular Ocean Data Assimilation System temperature and salinity profiles derived from altimetry and sea surface temperature data. The model is forced by daily heat and momentum fluxes, and therefore captures short-term wind events such as the Tehuantepec jet. Because the model has high horizontal resolution (~1/8 degree) and assimilates sea surface height data, it has a realistic representation of eddies and mesoscale variability. The ecosystem model includes two nutrients (nitrate and ammonium), two size-classes of phytoplankton, two size-classes of zooplankton, and detritus. The model is run for 4 years from 1999 to 2002, with analyses focused on 2000-2002. The model is validated using SeaWiFS data and ship-based observations from the STAR-cruises (Stenella Abundance Research Project) of 1999 and 2000. The northernmost and most intense of the wind jets along Central America is the Tehuantepec jet. The Tehuantepec jet is responsible for upwelling large amounts of nutrient rich water south of the Gulf of Tehuantepec. The jet also occasionally produce large anti-cyclonic eddies that transport organic matter away from the coast. Because organic matter that is transported into the open ocean will eventually sink to the deep ocean, this has implications for the carbon export in this region. The model results are used to calculate cross-shelf fluxes in this region in order to estimate how much organic material is transported across the shelf break. Results show that at the Gulf of Tehuantepec there is high offshore export of organic material, particularly during eddy generation events, but also in fall. The highest export is on the order of 10 Mg C per meter of coastline per day and happens during eddy events. During these events there is a comparable onshore flux to the south of the gulf. Typically there is onshore flux to the south of the gulf during the summer. The model estimated transport away from the coast at the Gulf of Tehuantepec is 167 Tg C/year, and the onshore transport to the south of the gulf is 704 Tg C/year. The second subject of interest is the CRD. In this region, upwelling at the surface is caused by Ekman upwelling during the summer, although the dome is thought to be present at depth throughout the year. The doming of the isotherms below the thermocline is a result of vortex stretching and is decoupled from the wind-driven processes at the surface. A mass-balance budget is calculated at the CRD, and the horizontal and vertical fluxes are related to the abundance of plankton at the dome. There is upwelling (7.2X10-2 Sv ) at the dome throughout the year, but around the location of the dome (90° W), the upwelling is largest in the winter. Further west, input of nutrients from below is larger in the fall and summer. The results suggest that about 80% of the nitrate that is supplied to the dome during summer is actually brought up to the west of the dome and transported eastward by the North Equatorial Counter Current. / A Dissertation Submitted to the Department of Oceanographyin Partial Fulfillment of Therequirements for the Degree ofdoctor of Philosophy. / Spring Semester, 2005. / March 14, 2005. / Physical-Biological Interactions, Marine Ecosystem Modeling, Pacific Ocean, Gulf Of Tehuantepec, Costa Rica Dome, Cross-Shelf Transport, Eddies / Includes bibliographical references. / James J. O'Brien, Professor Directing Dissertation; Gordon Erlebacher, Outside Committee Member; William K. Dewar, Committee Member; Nancy H. Marcus, Committee Member; Richard L. Iverson, Committee Member; Eileen E. Hofmann, Committee Member.

Submarine groundwater discharge (SGD) assessments conducted both in the laboratory and at a field site in the northeastern Gulf of Mexico, using a continuous-heat type automated seepage meter (seepmeter) have shown that the device has the potential of providing long-term, high-resolution measurements of SGD. The improvements on the device using a simple inexpensive laboratory set up, have shown that: (1) connecting an extension cable to the seepmeter has a negligible effect on its measuring capability and, (2) influence of very low temperature (≤ 3 ºC) on seepmeter measurements can be accounted for by conducting calibrations at such temperatures prior to field deployments and, (3) salinity had no significant effect on the performance of the seepmeter. Calibration results from fresh water and sea water showed close agreement at a 95% confidence level significance between the data sets from the two media (R2 = 0.98). The observed artifacts on seepmeter measurements associated with Bernoulli-induced flow, the vertically directed flow arising due to water movement across topographic features can significantly be reduced by burying (or submerging) the seepmeter to nearly the same level as the sediment topography. While the study revealed that in general wind speeds > 6 m/s were associated with enhanced SGD measurements in seepmeters with buried and unburied benthic chambers, the influence was greater in the unburied meters, and more pronounced for SGD rates 6 m/s were associated with enhanced SGD measurements in seepmeters with buried and unburied benthic chambers, the influence was greater in the unburied meters, and more pronounced for SGD rates Study of the Sarasota Bay (SB) system revealed SGD advection rates ranging from 0.7 to 24.0 cm/day, except for rare isolated hot spot occurrences where higher rates were observed. In general, SGD estimates were relatively higher in the middle and south regions (5.9 – 24.0 cm/day) compared to the north region (0.7 – 5.9 cm/day). Although no obvious seawater nutrient concentration trend was revealed, the average N/P ratio was higher in the north compared to the middle and south regions of the SB system. The importance of SGD was evident in that about 40% of the regional nutrient fluxes were observed in the north while ~ 60% occurred in the middle and south regions combined. The latter two regions also had the highest overall nutrient flux per water volume ratio, compared to the north region, thus making them potentially more vulnerable to eutrophic conditions. On average, we estimate about 27% of total dissolved N in the SB system was derived via SGD. / 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, 2010. / August 26, 2010. / hydrology, Submarine groundwater discharge, groundwater, seepage meter, seepage meter artifacts, Florida, nutrients, nutrient fluxes, marine environment, nearshore, processes, measurements, coastal zone, Turkey Point, Sarasota, groundwater discharge quantification, Gulf of Mexico, biogeochemistry / Includes bibliographical references. / William C. Burnett, Professor Directing Dissertation; Xiaolong Bill Hu, University Representative; Jeffrey P. Chanton, Committee Member; William M. Landing, Committee Member; Joel E. Kostka, Committee Member.

This study has evaluated an existing hybrid three-dimensional variational ensemble transform Kalman filter (3DVAR-ETKF) ensemble data assimilation system using the Weather Research and Forecasting (WRF) model in realistic numerical weather prediction experiments. The study was divided into three parts: Part one assessed the skill of the ETKF ensemble generation scheme with and without implicit mode error included in the ensemble. Part two assessed the benefit of including flow-dependent information into the hybrid cost function. Part three proposed an alternative to ETKF and tested its performance in cycling experiments. The ETKF perturbations as an ensemble-generation scheme performed well in single and multi-physics ensemble approaches. The multi-physics ETKF ensemble performed best maintaining the appropriate variance and dependence on covariance inflation. The multi-physics ETKF ensemble was characterized by larger (smaller) error growth (reduction) during the model integration than the single-physics ensemble. Using the ensemble mean as the first guess in the 3DVAR cost function significantly improved the skill of the analyses. Tuning the static 3DVAR background error covariances using the ETKF ensemble perturbations instead of time-lagged perturbations improved the skill of the deterministic and ensemble 3DVAR analyses as measured by 12- through 48-h deterministic forecast skill. Incorporating ensemble-based flow-dependent error covariances from limited 20-member ensembles into the hybrid cost function added skill to the analyses. This added skill was in addition to that achieved by using the ensemble mean as the first guess and using the tuned background error covariances. The greatest improvements in analysis skill were observed when a multi-physics ensemble was used to supply the error covariances to the hybrid cost function. Vertical localization added some skill to the analyzed wind speeds, mostly at longer lead times and when the localization length scale is less restrictive. The proposed hybrid Lanczos ensemble filter (HLEF) ensemble generation scheme was shown to be equivalent to the ETKF scheme when no inflation was applied and the HELF perturbations did not include the effect of covariance localizations or hybridization. Both vertical and horizontal covariance localization in the HLEF perturbations ameliorated the under estimation of analysis uncertainty. 10-day cycling experiments with inflated and localized HLEF perturbations required less than 30% of the magnitude of the inflation required by ETKF. Experiments that addressed the possibility of producing analysis perturbations that are consistent with the hybrid variational cost function produced encouraging results. / A Dissertation Submitted to the Department of Earth, Ocean and Atmospheric Sciences in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy. / Spring Semester, 2011. / March 28, 2011. / Physics Uncertainty, 3DVAR, Hybrid, Lanczos, ETKF, Ensemble Data Assimilation, Data Assimilation / Includes bibliographical references. / Henry E. Fuelberg, Professor Directing Dissertation; I. Michael Navon, University Representative; Robert Hart, Committee Member; Jon E. Ahlquist, Committee Member; Xiang-Yu Huang, Committee Member; Guosheng Liu, Committee Member; P. Anil Rao, Committee Member.

Submarine groundwater discharge (SGD) is an important pathway for trace element and nutrient cycling in the coastal ocean. I use a combination of hydrological and geochemical tracer observations to gain insights into the natural and anthropogenic mechanisms driving SGD into coastal water bodies. Nutrient measurements in a subterranean estuary (STE) were used to discuss the biogeochemical controls of SGD endmember concentrations and to derive inputs associated with fresh and saline SGD. 222Rn, CH4, and associated variables in seawater were monitored nearly continuously at a coastal site in the Gulf of Mexico for almost two years. Surprisingly, the variability of 222Rn and CH4 over short (e.g., hourly) time scales was generally comparable to or even more pronounced than fluctuations over much longer (e.g., monthly) time scales. While high tracer concentrations usually occurred during low tide and low tracer concentrations during high tide, this pattern was occasionally inverted or absent indicating that no single model can be used to describe the entire dataset. This implies that seasonal investigations of SGD tracers in the coastal ocean may be masked by short-term variability. Modeled SGD patterns were strongly associated with the neap-spring tidal cycle, at least during a period of extreme drought when minimum external disturbances were present. Multiple independent approaches used to separate the relative contribution of fresh and saline SGD indicated that transient marine forces, likely tidal pumping, dominate benthic advective exchange at this coastal plain site. I also tested whether biogeochemical processes in a STE alter nutrient concentrations that are discharged into the ocean via SGD. Nutrient distributions were consistent with a sequence of reactions in a narrow (~2 m) surface layer where nitrate is initially exhausted (likely due to denitrification), organic nitrogen is remineralized releasing ammonium, and some DOC remains. Nutrient cycling in this STE was primarily fueled by oxygen and labile organic matter supplied by tidal pumping of seawater into the coastal aquifer. Even though fresh SGD accounted for only ~5% of total volumetric additions, the interaction between fresh SGD with components in the STE provided 22-34% of DOC and ~50% of nitrogen inputs, with the remainder associated with recirculated seawater. While SGD volumetric inputs are similar seasonally, changes in the biogeochemical conditions of this coastal plain STE led to higher summertime nutrient fluxes, suggesting a link between coastal primary productivity and nutrient production. Finally, I applied naturally-occurring geochemical tracers (222Rn, 223Ra, 224Ra, 226Ra, CH4, 18O, and 2H) to assess anthropogenic-driven groundwater discharge in Mangueira Lagoon, Brazil. Modeling of radon inventories indicated that groundwater advection rates in the numerous irrigation canals are 2 orders of magnitude higher than along the lagoon shoreline. In spite of the relatively small area of the canals, they contributed nearly 70% of the total (~57,000 m3/d) groundwater input into the entire Mangueira Lagoon. Dredging of these canals cut through aquitards which previously restricted upward advection from the underlying permeable strata. In spite of the small volume contribution (~2% of precipitation), groundwater accounted for 50-70% of major ion inputs into the lagoon. The irrigation channels may therefore represent an important but previously overlooked source of nutrients and other dissolved chemicals derived from agricultural practices into this and other lagoons. / A Dissertation Submitted to the Department of Oceanography in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy. / Fall Semester, 2008. / October 16, 2008. / Radon, Nutrients, Geochemical Tracers, Permeable Sediments / Includes bibliographical references. / William C. Burnett, Professor Directing Dissertation; Jeffrey Chanton, Professor Co-Directing Dissertation; Bill Hu, Outside Committee Member; Thorsten Dittmar, Committee Member; Philip Froelich, Committee Member; Markus Huettel, Committee Member.

Mid-ocean ridge interactions with hotspots strongly affect mantle flow processes. This study analyses the anomalies produced as a result of the interaction between a hotspot and an oceanic ridge-ridge-ridge triple junction, in close proximity to one another. The complex three dimensional (3D) nature of the Azores Triple Junction (ATJ), in which two near-collinear faster-spreading ridges are joined orthogonally with a slower-spreading ridge, provides an excellent opportunity to quantify the effect of triple junction geometry on along-axis magmatic accretion and mantle dynamic processes as a result of the interaction with a hotspot. For the ATJ, the faster-spreading ridges are two branches of the Mid-Atlantic Ridge (MAR), and the slower-spreading ridge is the Terceira Rift (TR). Using shipboard bathymetry and satellite free-air gravity, we obtain mantle Bouguer anomaly (MBA) by eliminating from free-air gravity the attractions of seafloor topography and a reference crust. Along the TR, the Azores hotspot has a maximum MBA axial gravity low of -100 mGal, suggesting localized crustal thickening, elevated mantle temperatures and/or low density mantle. The entire Azores plateau along the TR is associated with a large (~80 mGal) broad low. Dispersion of plume material along the TR, a distance in the range of 550 km, is likely minimized by the rift system's obliqueness, immature nature and hyper-slow spreading rate, as well as the presence of the Gloria Fracture Zone. Further, along-axis profiles along the TR suggest that MBA shows a strong dependence on the tectonic segmentation of the ridge axis. / A Thesis Submitted to the Department of Geological Sciences in Partial Fulfillment of the Requirements for the Degree of Master of Science. / Spring Semester, 2009. / March 6, 2009. / Lithosphere, Geochemical, Crust, Compositional, Oceanic, Continental, Volcanism, Tomographic / Includes bibliographical references. / Jennifer Georgen, Professor Co-Directing Thesis; Jim Tull, Professor Co-Directing Thesis; Vincent Salters, Committee Member; William Parker, Committee Member.

The Citronelle Formation is the most widely occurring, surficial geologic unit along the northeast Gulf of Mexico. It is a siliciclastic unit consisting primarily of sands and gravels with varying amounts of clay and minor amounts of mica and heavy minerals. Historically, the unit has been thought to be a fluvial deposit of Pliocene age. Evidence presented here suggests, at least in part, a marine origin. In some pits and exposures in southern Walton and Okaloosa Counties in western Florida, sediments that are referred to the Citronelle Formation contain well preserved Ophiomorpha, bivalve mollusk casts, shark teeth, terrestrial vertebrate fossils and other trace fossil remains. Various types of bedding, including cross bedding, occur. These apparent nearshore marine depositional facies are the focus of this investigation which will attempt to determine the paleo- environmental depositional regimes, age, and how this facies relates to the Cirtonelle Formation. Field work was conducted and data were gathered from exposures and outcrops within the study area. Stratigraphic sections were measured and described. Where feasible, sediment samples were collected for sieve analysis. Further sampling of trace fossils (Ophiomorpha) and body fossils was conducted for analysis. Cross-bedding orientation was recorded from one locality to determine predominant paleo-current direction. These data, when combined, support the hypothesis that these sediments that have been mapped as Citronelle Formation represent nearshore, marine facies. However, their placement in the Citronelle Formation still remains questionable due to the lithologic similarity of overlying and underlying units. / A Thesis submitted to the Department of Geological Sciences in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2009. / April 7, 2009. / Granulometry, Siliciclastic, Ophiomorpha, Citronelle / Includes bibliographical references. / Sherwood W. Wise, Professor Directing Thesis; Anthony J. Arnold, Committee Member; Joseph F. Donoghue, Committee Member; Stephen J. Kish, Committee Member.

Ice and snow particles have a great, yet poorly understood impact on the Earth's climate system. One of the difficulties of studying snow particles is their irregular shape. While spheres and even oblate spheroids backscatter radiation in a consistent manner, irregularly shaped objects do not. Due to the complexities of snowflakes, they are often assumed to be spherical for both satellite retrieval and modeling purposes. This can introduce error in many studies. While there are several aggregate snowflake models in existence, many use spheres as a building block for the snowflake. This is inaccurate as most snowflakes are comprised of a combination of bullet rosettes, plates, columns, and dendritic snow crystals. Furthermore, most studies do not have constraints in place to make sure that snowflakes are of the correct size and density as observed from field studies. None of the theoretical models examined in this study analyze the single-scattering properties of the flakes. In order to improve upon previous models, this study creates an aggregate snowflake using 200 ìm and 400 ìm 6-bullet rosette crystals. These crystals and resultant flakes are required to follow established size-density relationships obtained from numerous field studies. In addition, the flakes must also be of similar fractal dimension determined from other case studies. The single-scattering properties of these flakes are then determined from the discrete dipole approximation. / A Thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2010. / April 13, 2010. / dda, Extinction Coefficient, Scattering Coefficient, Absorption Coefficient / Includes bibliographical references. / Guosheng Liu, Professor Directing Thesis; Robert G. Ellingson, Committee Member; Paul Ruscher, Committee Member.

The tectonic separation of Australia from Antarctica is a key constraint on the development of the Antarctic Circumpolar Current (ACC) during the Cenozoic. The ACC plays a critical role in global climate thermally isolating Antarctica and its initiation is hypothesized to have crossed a critical global climate boundary resulting in initial Antarctic ice sheet growth (Kennett, Houtz et al., 1975; Exon, Kennett, Malone et al., 2001). The relatively shallow Tasmanian Gateway is one of the few places in the Southern mid to high latitudes where fairly complete, carbonate-rich sequences can be drilled detailing development of the ACC. The upper Oligocene and Miocene sediments recovered by Ocean Drilling Program (ODP) Leg 189 are rare when compared to other Southern Ocean drilling sites in terms of biotic richness and continuous sedimentation through the Miocene (Exon, Kennett, Malone et al., 2001). The Miocene has been characterized as a warm interval with significant cooling taking place in the middle Miocene with the permanent emplacement of the East Antarctic Ice Sheet (EAIS) (Shackleton and Kennett, 1975). Evidence for periods of ice sheet growth and decay prior to the mid-Miocene permanent emplacement of the EAIS include deep-sea oxygen isotope records (Miller et al., 1987) correlated with major sequence boundaries (Haq et al., 1987) and glacimarine sediments deposited on the Antarctic margin (Cape Roberts Science Team, 1999; Roberts et al., 2003). Climatic conditions fluctuated in the early Miocene peaking in warmth at the mid-Miocene Climatic Optimum (~16Ma). A major shift in the stable isotope records at ~14 Ma marks a significant phase of ice growth on Antarctica (Kennett and Shackleton, 1975). This cooling trend continued and by the middle/late Miocene the development of oceanic fronts was well established in the Tasmanian and New Zealand sectors of the Southern Ocean (Exon, Kennett, Malone et al., 2001; Nelson and Cooke, 2001). This dissertation interprets the calcareous nannofossil assemblage data, coupled with robust age models, geochemical and sedimentological data, in order to reconstruct the paleoceanographic conditions in the Tasmanian Gateway during the Miocene. Comparisons between study sites in the Tasmanian Gateway, as well as with other Miocene sections, provides a detailed view of changing paleoceanographic conditions in the Tasmanian region as Australia and Antarctica continued to separate, the ACC and oceanic fronts in the Southern Ocean fully developed and ice volume on Antarctica waxed and waned. A robust calcareous nannofossil biostratigraphy was constructed at ODP Sites 1168, 1170-1172, despite the lack of key marker species from the Discoaster, Sphenolith and Triquetrorhabdulus genera. Diversity was typical of a temperate-water setting, though Site 1168 had higher diversity than the other three sites. Several alternative markers not employed by the Okada and Bukry (1980) zonal scheme were tested and allowed for further subdivision of the stratigraphic column, though not all Miocene calcareous nannofossil zones could be identified. Core disturbance and bioturbation did complicate the interpretation of the sedimentary history, particularly in the upper Miocene and across the Miocene/Pliocene boundary. The robustness of the calcareous nannofossil biostratigraphy was further tested by comparison to biomagnetostraphic data from foraminifers, diatoms, dinocysts, and radiolaria. Second-order bioevents, used to increase the zonal resolution, were compared and found to represent reliable bioevents in the Tasmanian region. Fluctuations in the relative abundances of Coccolithus pelagicus and Reticulofenestra perplexa indicate similar surface water conditions across the study area from ~ 8-12 Ma. Site 1172 is apparently warmer than the other sites beginning at ~ 8 Ma possibly caused by the inception of the proto-East Australia Current. Detailed analysis of calcareous nannofossil assemblage fluctuations across the Oligocene/Miocene boundary (O/M) at Site 1168 support the supposition that the Mi-1 event was a brief glacial associated with only a couple degrees of cooling (Zachos et al, 2001; Roberts et al., 2003) and accompanied by increased productivity (Pollard and DeConto, 2003). Biostratigraphy across the O/M boundary at other Leg 189 Sites indicates increased current activity by the ACC. Analysis of the sediments across the O/M boundary did not reveal any fluctuations at orbital frequencies. The bioturbated and disturbed nature of the cores across the O/M boundary at Site 1168 prevent further analysis at orbital time scales. Sediments recovered by ODP Leg 189 do provide sufficient resolution to create a detailed Southwest Pacific/Southern Ocean temperate-water Miocene calcareous nannofossil biostratigraphy and paleoecological reconstruction. / A Dissertation submitted to the Department of Geological Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester, 2007. / March 26, 2007. / Biostratigraphy, ODP Leg 189, Quantitative Biostratigraphy, Oligocene/Miocene Boundary, Antarctic Circumpolar Current / Includes bibliographical references. / Sherwood W. Wise, Jr., Professor Directing Dissertation; Richard Iverson, Outside Committee Member; Neil Lundberg, Committee Member; Yang Wang, Committee Member; Joseph Donoghue, Committee Member.