Doctor of Philosophy, The Ohio State University, 2022, Geodetic Science

Satellite altimetry has been the de facto technique for estimating barotropic tides over the global oceans, with solutions either assimilated or directly employed to develop of hydrodynamic and empirical barotropic ocean tide models. However, solutions remain poorly estimated over the marginal seas owing to their semi-enclosed geometric configuration featuring abrupt changes in bathymetry and proximity to land masses. These regions are also largely influenced by non-tidal variability changes due to ocean circulation processes with periods ranging from days to several years. High-frequency motions arising from these processes are difficult to observe due to the inherent sub-optimal sampling from satellite altimeters, resulting in spatio-temporal aliasing errors. Conversely, low-frequency motions, though observable from satellite altimeters, can add significant noise to their observations. This dissertation introduces a case study in the Gulf of Mexico (GoM). In this region, the non-tidal variability can attain satellite altimetry sea surface height anomaly (SSHA) root mean square (RMS) values exceeding 30 cm in highly energetic areas. Furthermore, a global barotropic ocean tide model intercomparison suggests that these effects have been neglected even in the best performing models, thus resulting in poorly estimated barotropic tides. Consequently, this dissertation aims to identify and remove quasi-periodic non-tidal signals contaminating altimetry observations to further improve the estimation of barotropic tides over the marginal seas. This study proposes an experimental non-tidal variability correction for altimetry data based on a combination of numerical solutions from an ocean circulation model and a model of oceanic sea-level anomalies. The empirical orthogonal function (EOF) analysis method is employed to identify and correct altimetry observations for quasiperiodic non-tidal variability signals. After correcting the altimetry observati (open full item for complete abstract)

Committee: C.K. Shum (Advisor); Michael Durand (Committee Member); Demián Gómez (Committee Member); Michael Bevis (Committee Member) Subjects: Earth; Environmental Science; Geophysics; Oceanography; Remote Sensing

Bachelor of Science, Wittenberg University, 2021, Biology

Coral reefs are vital ecosystems that are experiencing high stress and death rates from major bleaching events. Because of the major loss of corals around the world, restoration and methods of measuring the effectiveness of restoration techniques have become imperative. Photomosaics, also known as Structure-from-motion technology, is a new measuring method for the restoration of coral reefs. This technology combines thousands of overlapping photos of reefs and allow for definitive measurement and analysis of reefs. CoralNet is a self-learning website that more efficiently labels coral. In this research, CoralNet is used to analyze both restored and unrestored reefs in Puerto Rico. The unrestored reefs are found to have the most diversity in coral species, but a restored reef has the highest H value of 1.584. Restored reefs were also found to have more hard corals whereas the unrestored reefs were found to have more soft corals. Overall, SfM technology is recommended for use to measure coral biodiversity and outplant growth.

Committee: Jim Welch (Advisor); Raymond Dudek (Committee Member); Matthew Collier (Committee Member) Subjects: Aquatic Sciences; Biological Oceanography; Biology; Ecology; Environmental Science; Oceanography

Doctor of Philosophy, The Ohio State University, 2021, Atmospheric Sciences

The climate change during the last deglaciation is characterized by several abrupt fluctuations, notably the Heinrich Stadial 1 (HS1, ~18-14.5 ka), Bølling-Allerød (BA, 14.5-12.9 ka), and Younger Dryas (YD, 12.9-11.7 ka). These abrupt events as well as long-term climate variability are well preserved in stable water isotope (훿18푂) proxies over Asia and Greenland. Yet, some long-standing puzzles regarding the evolution of the water isotopes and their implications to the climate remains not well understood. In particular, the absence of the onset signal of the HS1 cold event around 18 ka in Greenland ice core oxygen isotope 훿18푂 records appears to be inconsistent with other climate proxies around the globe that do show a clear HS1 onset; the mechanism and hydroclimate implication of highly coherent speleothem 훿18푂c (훿18푂 in stalactite) across the Asian monsoon regions remain a subject of debates. To decipher the evolution of water isotope and climate in the last deglaciation, an isotope-enabled Transient Climate Experiment (iTRACE) of global climate and water isotopes in a state-of-the-art isotope-enabled Earth system model is conducted. The iTRACE successfully reproduces the oxygen-isotope evolutions across the pan-Asia and Greenland in the last deglaciation. It is found that the oxygen-isotope evolution is determined by a compensation between accumulation effect associated with summer-winter precipitation contrast, and water isotopic composition effect associated with oxygen-isotope in rainfall. Over Greenland, the isotopic composition effect plays a dominant role during the much of the deglacial time, while the opposite accumulation effect becomes comparable around the onset of HS1 that produces a muted onset in ice core 훿18푂. Further investigation suggests that the deglacial ice-core isotope variability is mainly modulated by the sea ice extent in the North Atlantic that controls moisture and energy supply to Greenland. Across the (open full item for complete abstract)

Committee: Zhengyu Liu (Advisor); Lonnie Thompson (Committee Member); David Bromwich (Committee Member); Bryan Mark (Committee Member) Subjects: Atmospheric Sciences; Oceanography; Paleoclimate Science

Doctor of Philosophy, The Ohio State University, 2021, Earth Sciences

The distribution and abundance of coral reef ecosystems is declining globally due to the detrimental impacts of climate change. As the surface ocean becomes warmer and more acidic, corals must adapt or acclimatize in order to survive and persist. The overarching goal of my dissertation was to evaluate the biological processes that lead corals to adapt and acclimatize to the levels of ocean warming and acidification expected later this century. Following a review of 255 coral heat-stress experiments conducted over the last thirty years (Chapter 2), I identified several gaps in our knowledge of coral bleaching. For instance, the majority of experimental coral bleaching research has been conducted on only three Scleractinian coral species, many reef regions worldwide are critically understudied, and the literature is heavily biased towards adult life stages (as opposed to gametes, larvae, recruits). Similarly, the majority of studies are short-term in duration (i.e., < 7 days) and focus on only one or two aspects of coral biology (e.g., calcification or photosynthetic efficiency). Thus, our understanding of the long-term impacts of global climate change on coral holobiont physiology is lacking. To better understand the link between holobiont physiology and the environment, I conducted a comprehensive survey of Oʻahu coral reefs (Chapter 3), including eight species collected from six reef locations. I found that environmental gradients of temperature, significant wave height, and seawater chlorophyll concentration were strongly correlated with the physiological profiles of Hawaiian corals, though the strength of this relationship was species specific. My results indicate that Montipora capitata and Pocillopora acuta have the most physiological variance along environmental gradients, suggesting a higher capacity for adaptation or acclimatization. Conversely, Porites evermanni and Pocillopora meandrina have the least physiological variance which does not correlate strongl (open full item for complete abstract)

Committee: Andréa Grottoli (Advisor); Agustí Muñoz-Garcia (Committee Member); Lawrence Krissek (Committee Member); Robert Toonen (Committee Member); Noah Weisleder (Committee Member) Subjects: Biogeochemistry; Biology; Climate Change; Earth; Ecology; Environmental Science; Oceanography

Doctor of Philosophy, The Ohio State University, 2020, Geological Sciences

The tropics (±23.5° latitude) are a rapidly developing and highly populated region, expected to contain 50% of the Earth's population by 2040. Rapid growth has led to deforestation and the removal of soil-binding vegetation, which exacerbates erosion issues. Erosion and deposition also dampen aquatic ecosystem function, degrade water quality, and disrupt food webs. Given the projected increased rainfall, anthropogenic development, and population, it is critical to understand connected watershed erosion and coastal deposition in tropical systems. However, many risk assessment methods are on the regional or watershed scale and none endeavor to connect watershed erosion and coastal deposition. Here, I present the first erosion and deposition vulnerability index to connect watersheds and coastal zones while covering all tropical regions and using open-source data focused on anthropogenic land use. Importantly, coastal deposition cannot be quantified on a tropical scale, but is calculated at the watershed scale. I find that tropical watersheds with high occurrences of earthquakes, steep slopes, and high annual precipitation are most vulnerable to erosion, and that these combined characteristics are most prevalent in the Caribbean and Southeast Asia. The overall vulnerability of a watershed and coastal zone system can change drastically when connecting watershed erosion to coastal deposition. The erosion and deposition vulnerability index is effective for larger scale analyses, but small tropical islands are often overlooked or misclassified due to the low-resolution of global datasets used. There are ~45,000 small tropical islands (<1,000 km2) scattered across the Pacific, Atlantic, and Indian Oceans with ~115M people living on them. On these islands erosion and deposition issues are of paramount importance because of the impact on their sediment-intolerant coastal ecosystems, which sustain their economies. I focus on one such system on St. John in the US Virgin Is (open full item for complete abstract)

Committee: Derek Sawyer PhD (Advisor); Anne Carey PhD (Committee Member); Michael Durand PhD (Committee Member); Lawrence Krissek PhD (Committee Member) Subjects: Geology; Geomorphology; Marine Geology; Oceanography

Master of Science (MS), Wright State University, 2019, Biological Sciences

The coral reefs within Indonesia's Wakatobi Marine National Park support a high diversity of reef-building hard corals and associated marine fish. Climate change threatens to dramatically affect coral reef ecosystems by altering the interactions between reef fish and the specific microhabitats they depend on for survival. To examine the spatially varied effects of habitat complexity on the community composition and trophic structure of marine fish assemblages, I analyzed fish community and habitat complexity data across reef zones. Habitat complexity metrics were: structural complexity, the percentage of hard coral (HC) cover, HC genera richness, HC genera diversity (Shannon index), and HC growth form diversity (Shannon index). The community composition of fish assemblages was significantly positively related to habitat complexity, reef zones, and reef systems. This study found that the overall direction and strength of relationships between the fish community and coral reef habitat complexity data varies spatially between reef zones. Marine conservation and restoration efforts need to include specific management plans that vary among reef zones based on how varied habitat complexity and fish communities are at local scales.

Committee: Volker Bahn Ph.D. (Advisor); Thomas Rooney Ph.D. (Committee Member); Lisa Kenyon Ph.D. (Committee Member); Leonard Kenyon M.S. (Other) Subjects: Biology; Ecology; Environmental Management; Environmental Science; Natural Resource Management; Oceanography

Doctor of Philosophy, The Ohio State University, 2019, Earth Sciences

The Arctic is warming at increasingly rapid rates as a consequence of current global climate change. Temperature increases are amplified at these high latitudes and have resulted in major environmental changes, especially pronounced in the continual decline of sea ice at the surface of the Arctic Ocean. Through atmospheric and oceanic connections, these effects have been linked to many of the climatic changes taking place around the world. In addition, sea ice loss has major societal impacts, as it allows for increased human activity in the Arctic Ocean region. Therefore, it is necessary to improve our understanding of the changing Arctic system, which requires a profound knowledge on its history on various time scales, from decades to millions of years. This dissertation investigates multiple sedimentological proxies from the western Arctic Ocean, with a focus on reconstructing paleoenvironmental conditions during the Pliocene and early Pleistocene (Plio-Pleistocene; ~5-0.8 Ma). This time period preceded the expansion of major Northern Hemisphere glaciations (~0.8 Ma) and potentially represents one of the most useful paleo-analogs for the changes currently taking place in the Arctic Ocean. Two sediment cores from the Northwind Ridge north of Alaska were analyzed in detail, as they recovered material dating back to the Pliocene and exhibit uniquely good preservation of calcareous microfossils, primarily benthic foraminifera. These microfossils aided in constructing a better resolved Plio-Pleistocene stratigraphy for the Arctic Ocean, and they provided a proxy for reconstructing paleo-sea ice conditions by relating the distribution of specific ecological groups to sea-ice extent. Other proxies, such as sediment texture (grain size) and elemental composition (X-ray Fluorescence) were used to interpret paleo-circulation and sediment transport processes. Together, these proxy records indicate that the Pliocene and early Pleistocene environments had little effect from (open full item for complete abstract)

Committee: Andrea Grottoli (Advisor); Leonid Polyak (Advisor); Lawrence Krissek (Committee Member); Cinnamon Carlarne (Committee Member) Subjects: Oceanography; Paleoclimate Science; Sedimentary Geology

Doctor of Philosophy, The Ohio State University, 2019, Microbiology

The Arctic system has been undergoing a rampant change during the Anthropocene. This anthropogenic change has allowed for additional physical and biological positive feedback processes that in turn accelerate warming in the arctic and subarctic systems. Microbial community/functional dynamics are both (i) dramatically impacted by these rapid changes and (ii) key players in the biological positive feedback process that accelerates the change. Recent technological, analytical, and computational advances have allowed us to ask systems-level questions that encompass microbial and viral community dynamics (along with their potential functional dynamics) and high-resolution environmental measurements. This research took a systems-level approach to look for the first time at (i) the characteristics of Arctic marine viruses in a global context, and (ii) microbial community gene expression in a rapidly changing permafrost thaw gradient. Additionally, novel viral sequences recovered from the marine and terrestrial ecosystems studied here were used to build new resources and tools that accelerate viral discovery in nature. First, studying marine viral macro- and microdiversity from the Arctic Ocean to the Southern Ocean, enabled by the Tara Oceans Expedition, revealed the Arctic Ocean as a hotspot of viral diversity, with ~42% of the recovered viral populations originating from the Arctic Ocean viromes. In total 195,728 viral populations >10 kb were recovered from the global ocean to constitute the Global Ocean Viromes 2.0 (GOV2.0) dataset. Viral communities assorted into five distinct global ecological zones and the arctic viral communities formed their own distinct ecological zone. Additionally, this work revealed unexpected patterns and ecological drivers of viral diversity (at the community, inter-, and intrapopulation levels), within the Arctic Ocean, across latitudes, and across the depth of the global ocean. Second, genome-resolved metaproteomic study of microbial gene (open full item for complete abstract)

Committee: Matthew Sullivan (Advisor); Virginia Rich (Advisor); Kelly Wrighton (Committee Member); Alvaro Montenegro (Committee Member) Subjects: Biogeochemistry; Bioinformatics; Biological Oceanography; Biology; Climate Change; Ecology; Environmental Science; Geobiology; Microbiology; Oceanography; Soil Sciences; Statistics; Virology

Master of Science, The Ohio State University, 2019, Atmospheric Sciences

Changes in the Antarctic Circumpolar Current (ACC) transport during the last deglaciation cycle are thought to have played an important role on global climate variability. A better understanding of ACC transport at the Last Glacial Maximum (LGM) would allow better assessment of ACC dynamics and past global-scale climatic variations. However, estimates of ACC transport vary widely among some LGM coupled ocean-atmosphere climate model simulations and proxy studies. As the ACC is in the thermal wind balance, oxygen isotopic ratios (d18O) in the foraminifera (d18Oc) are often used as a proxy to reconstruct past density variation and thus ACC transport. Here we test the ACC transport and its dynamics at the LGM (20 ka) in a transient simulation of the last deglaciation with the CESM (C-iTRACE) and examine the ability of the d18Oc gradient to reconstruct the density gradient to estimate LGM ACC transport. The model simulation suggests that the ACC transport was approximately 60% greater at the LGM (227 Sv) compared with that of today (145 Sv), which mainly results from the baroclinic transport. Furthermore, the d18Oc gradient at the LGM over the Southern Ocean tends to underestimate the LGM density gradient because the d18Oc gradient results primarily from temperature changes but the density gradient is highly affected by salinity changes due to sea ice formation. Therefore, although d18Oc gradient is a powerful tool to reconstruct past density, it likely underestimates the Southern Ocean density gradient at the LGM and it hence to underestimate the ACC transport.

Committee: Zhengyu Liu (Advisor); Alvaro Montenegro (Committee Member); Ellen Mosley-Thompson (Committee Member) Subjects: Oceanography; Paleoclimate Science

Doctor of Philosophy (PhD), Wright State University, 2018, Environmental Sciences PhD

Mercury (Hg) is a global pollutant toxic to humans and wildlife. Monomethylmercury (MMHg) is a bioavailable compound that bioaccumulates and biomagnifies in food webs. Humans are primarily exposed to MMHg from seafood consumption (Sunderland 2007), and high quantities of the neurotoxin lead to reduced neurocognitive functioning in adults and the children of exposed mothers (Cohen et al. 2005, Yokoo et al. 2003). Negative effects from MMHg accumulation on the health of humans and wildlife requires a more complete understanding of the chemistry and microbiology driving Hg methylation in both marine and freshwater systems. This work focuses on water column distribution, speciation, and methylation of Hg. The aims of this dissertation are three-fold: (1) characterize the speciation and distribution of Hg in the western Arctic Ocean; (2) examine seasonal variations in Hg speciation, methylation, and demethylation, and the microbial communities of Hg methylators in Crystal Lake, Ohio; and (3) quantify Hg methylation rates and characterize methylating microbial communities in waters on the continental shelf of the northwest Atlantic Ocean. While Hg methylation has been studied for decades, this work is built upon recent improvements in Hg detection limits, and newly discovered genes responsible for Hg methylation. In conjunction with U.S. Arctic GEOTRACES (GN01), the western Arctic Ocean was sampled in the summer of 2015. Although Hg concentrations in the Canada and Eurasian Basins were low relative to the Atlantic and Pacific Oceans, higher MMHg concentrations were observed in Arctic seawater that recently interacted with continental margins. We estimate that the Arctic Ocean receives 4–71 kmol Hg yr−1 from the Bering Strait, which is likely to interact with sediments of the shallow continental shelves before entering into the Arctic Ocean. This is potentially important, because while the estimated atmospheric input to the Arctic Ocean is ~400 kmol Hg yr−1, inflowing H (open full item for complete abstract)

Committee: Chad Hammerschmidt Ph.D. (Advisor); William Fitzgerald Ph.D. (Committee Member); Carl Lamborg Ph.D. (Committee Member); Mark McCarthy Ph.D. (Committee Member); Silvia Newell Ph.D. (Committee Member); Sarah Tebbens Ph.D. (Committee Member) Subjects: Biogeochemistry; Environmental Science; Limnology; Oceanography

Doctor of Philosophy, The Ohio State University, 2019, Earth Sciences

Tide gauges record relative sea level (RSL), i.e. the vertical position of the sea surface relative to the adjacent land mass or relative to the seafloor under the gauge. A tide gauge cannot distinguish between a rise in sea level or subsidence of the land or seawall or pier that supports the gauge. Absolute sea level (ASL) refers to the level or height of the sea surface stated in some standard geodetic reference frame, e.g. ITRF2008. Since satellite altimeters make a geometrical measurement of sea level, this constitutes a determination of ASL. Satellite altimeters suffer from instrumental drift and thus need to be calibrated using tide gauges. This requires us to estimate the rate of RSL change at each tide gauge and convert this into an estimate of the rate of ASL change. This is done using a GPS station located at or near the tide gauge, since it can measure the vertical velocity of the lithosphere – often referred to as vertical land motion, VLM – which allows us to exploit the relationship ASL = RSL + VLM. This goal has motivated geodesists to build dozens of continuous GPS (or CGPS) stations near tide gauges – an agenda sometimes referred to as the CGPS@TG agenda. Unfortunately, a significant fraction of all long-lived tide gauges – especially those in the Pacific - have also recorded non-steady land motion caused by earthquakes. Rather than simply delete such datasets from the agenda, this thesis explores a new analytical method, based on the concept of a geodetic station trajectory model, that allows us to compute RSL and ASL rates even at tide gauges affected by regional earthquakes. We illustrate this method using two tide gauges (PAGO and UPOL) and three GPS stations (ASPA, SAMO and FALE) located in the Samoan islands of the Southwest Pacific. In addition to managing the impact of large regional earthquakes, we also seek new approaches to reducing noise in RSL rate estimates by suppressing the higher frequency sea level changes associated with ocean (open full item for complete abstract)

Committee: Michael Bevis (Committee Chair); C.K. Shum (Committee Member); Loren Babcock (Committee Member); Michael Barton (Committee Member) Subjects: Earth; Geological; Geophysical; Geophysics; Geotechnology; Ocean Engineering; Oceanography

Doctor of Philosophy, The Ohio State University, 2017, Atmospheric Sciences

One of the largest ecosystem controls in the oceans is the presence of dissolved oxygen. As oxygen levels fall, both micro- and macroorganisms face shrinking habitats and potential mortality. There have been several periods in Earth history where oxygen levels have fallen to anoxic (dissolved O2 concentration < 10 µmol L-1) or hypoxic (< 60 µmol L-1) levels in certain ocean basins or within inland seas and some of these events could potentially be linked to mass extinction events. Several hypotheses exist regarding the depletion of oxygen, the spread of hypoxia-anoxia, and why the low oxygen events occur at certain points in the geologic record, including rapid climate warming, enhanced nutrient inputs, and modifications to the surface biological pump. Unfortunately, there is little agreement on which of these potential hypotheses caused individual events and what might impact the oxygenation of our oceans in the future. This dissertation will test hypotheses related to deep ocean oxygen using the University of Victoria Earth System Climate Model. The first set of experiments feature Late Ordovician winds and paleogeography and test the impacts of atmospheric CO2 and O2, ocean bottom topography, and nutrient loadings on deep ocean oxygen concentrations. The second set of experiments is also within the Late Ordovician, but tests the impacts of remineralization rates, detrital sinking velocities, and ocean surface albedo on ocean oxygenation. The final set of experiments tests the impacts of a warming climate on the oxygenation of near-future oceans, in addition to the impacts of detrital sinking velocities and ocean surface albedo. For the Late Ordovician, the factors most favorable for the spread of anoxia are reduced atmospheric O2, increased loadings of nitrate, and a reduction in ocean surface albedo. Climatic factors (namely, increased CO2) played little role in the spread of anoxia or the depletion of oxygen in these experiments. Similarly, phosphate, enhanc (open full item for complete abstract)

Committee: Alvaro Montenegro (Advisor); Bryan Mark (Committee Member); Michael Melchin (Committee Member); Ellen Mosley-Thompson (Committee Member) Subjects: Atmospheric Sciences; Biogeochemistry; Climate Change; Oceanography; Paleoclimate Science

Master of Science, University of Akron, 2016, Geology

This study focuses on understanding diagenesis within the sediments from the Grenada Basin, located within the southern Lesser Antilles Volcanic Arc. Sediment in this region include tephra-rich volcanic sands, hemipelagic mud sequences, and carbonate-rich sequences, and vary widely in their proportions over short depth (cm) intervals. A variety of dissolved constituents and sedimentary solid phases, including dithionite extractable iron and manganese are used here to constrain the diagenetic reactions occurring within the sediment package in the Grenada Basin. Core material was obtained during IODP Expedition 340, and for this study I focus primarily on five sites, U1394, U1395 and U1396 located in the northern region off the coast of Montserrat and U1399 and U1400 in the south, located off the island of Martinique. Pore fluid chemical compositions reflect heterogeneity in the dominance of reactions occurring within the sediment. Some sites clearly show evidence for alteration of volcanic material as an important diagenetic process while other sites appear to be dominated by carbonate precipitation or dissolution reactions. For example, at sites U1395, U1396, and U1400 increases in Ca mirror decreases in Mg, suggesting that alteration of volcanic matter is the dominant diagenetic reaction occurring. Dissolved minor element distributions (Si, Li, B, Rb) support this notion with Si and Li generally increasing and B and Rb generally decreasing. In contrast, at sites U1394 (upper 100 meters) and U1399, decreases in both Ca and Mg with depth suggest that carbonate precipitation is an important diagenetic process. Regardless of the main sediment type, organic carbon content is uniformly low with average values of 0.19 ± 0.11% for U1394, 0.13 ± 0.07% for U1395, 0.13 ± 0.06% for U1396, 0.28 ± 0.08% for U1399, and 0.23 ± 0.15% for U1400. Carbonate contents in the north are more variable, ranging between 1 and 80%, than cores in the south, 1 to 40%. These (open full item for complete abstract)

Committee: James McManus Dr. (Advisor); John Peck Dr. (Committee Member); Linda Barrett Dr. (Committee Member) Subjects: Geology; Oceanography

Master of Science (MS), Bowling Green State University, 2016, Geology

The spatial paleoceanography of the entire Western Interior Seaway (WIS) during the Cenomanian-Turonian Oceanic Anoxic Event has been reconstructed quantitatively for the first time using Geographic Information Systems. Models of foraminiferal occurrences—derived from Dempster-Shafer theory and driven by fuzzy sets of stratigraphic and spatial data—reflect water mass distributions during a brief period of rapid biotic turnover and oceanographic changes in a greenhouse world. Dempster-Shafer theory is a general framework for approximate reasoning based on combining information (evidence) to predict the probability (belief) that any phenomenon may occur. Because of the inherent imprecisions associated with paleontological data (e.g., preservational and sampling biases, missing time, reliance on expert knowledge), especially at fine-scale temporal resolutions, Dempster-Shafer theory is an appropriate technique because it factors uncertainty directly into its models. Locality data for four benthic and one planktic foraminiferal species and lithologic and geochemical data from sites distributed throughout the WIS were compiled from four ammonoid biozones of the Upper Cenomanian and Early Turonian stages. Of the 14 environmental parameters included in the dataset, percent silt, percent total carbonate, and depositional environment (essentially water depth) were associated with foraminiferal occurrences. The inductive Dempster-Shafer belief models for foraminiferal occurrences reveal the positions of northern and southern water masses consistent with the oceanographic gyre circulation pattern that dominated in the seaway during the Cenomanian- Turonian Boundary Event. The water-mixing interface in the southwestern part of the WIS was mostly restricted to the Four Corners region of the US, while the zone of overlap of northern and southern waters encompassed a much larger area along the eastern margin, where southern waters occasionally entered from the (open full item for complete abstract)

Committee: Margaret Yacobucci Dr. (Advisor); Peter Gorsevski Dr. (Committee Member); Andrew Gregory Dr. (Committee Member) Subjects: Earth; Geographic Information Science; Geography; Geology; Marine Geology; Oceanography; Paleoecology; Paleontology; Statistics

Master of Mathematical Sciences, The Ohio State University, 2016, Mathematics

Local discontinuous Galerkin (LDG) methods are in regular use in literature and industry to model conservation law type problems that contain spatial derivatives of higher order than one; such problems may often exhibit stiffness. Implicit-explicit (IMEX) time-stepping methods have also seen common use to efficiently solve problems which may have both stiff and non-stiff components. Only recently has work begun in the application of IMEX methods in conjunction with LDG methods to solve such problems. In this work we are particularly concerned with such an application with IMEX Runge-Kutta (RK) methods. We initially repeat recent error convergence and stability results by Wang, Shu and Zhang for a one-dimensional (1-D) convection-diffusion problem with LDG discretization in space and IMEX Runge-Kutta (RK) discretization in time. We also achieve new corresponding results for a likewise discretized two-dimensional (2-D) linearized shallow water problem, in which a constant eddy viscosity term introduces stiffness to the problem. Both our 1-D and 2-D problems are modeled inefficiently by purely explicit methods, with strict time-step restrictions imposed on each in this case, due to their stiffness. Using IMEX methods, one observes optimal error convergence rates as well as relaxed restrictions on time-step sizes in both problems. We present such results as well as additional experimental results such as comparisons of computational run-times and maximal time-steps for the purely explicit and IMEX cases on both types of problems with varying degrees of stiffness. We conclude that IMEX RK methods are more consistently efficient than the more commonly used standard explicit strong-stability preserving RK methods for the solution of stiff problems. We observe the relationship of efficiency and time-step improvements to the ratio of the degree of stiffness to non-stiffness of a problem in both one and two dimensions, similarly to results for maximal stable time-steps obtain (open full item for complete abstract)

Committee: Edward Overman Dr. (Advisor); Ethan Kubatko Dr. (Advisor) Subjects: Civil Engineering; Computer Science; Engineering; Fluid Dynamics; Hydrology; Mathematics; Oceanography

PHD, Kent State University, 2014, College of Arts and Sciences / Department of Earth Sciences

Reconstructing sedimentary processes associated with the deglacial events in the Chukchi Margin is necessary to evaluate the deglacial and Holocene flow regime in the Chukchi margin area, which was the purpose of this study. To provide context for the paleoceanographic reconstruction, the modern system was explored using multispectral band ratio analysis of the marine portions of Landsat images. Terrestrial processes were investigated using visual geomorphic description and unsupervised classification to define land cover classes and sediment sources. Thermal images and band ratios clearly demonstrate that flow regimes influence sediment transport, variations of the plant pigment, sea ice content and particle density. Using 1040 samples from five sediment cores and 27 surface samples from the Chukchi Margin, sediment composition was evaluated by comparison of visible and near infrared (VNIR) derivative spectroscopy, while sediment texture was explored using laser-particle grain size analysis. Varimax-rotated principal component analysis (VPCA) on several different multivariate data sets was employed to address the multi-colinearity inherent in this type of dataset. VNIR derivative spectroscopy was used to identify mineralogical compositions of dolomite + illite; goethite + chlorophyllide-a; smectite + chlorite and calcite in the Chukchi Margin area. Strong influence of Arctic Oscillation from the mid-Holocene to present enhanced the iron minerals with a provenance from Russian seas. Enhancement of the smectite + chlorite component during 6000 to 3500 yr BP exhibits an influx of Pacific waters related to mid Holocene Warming. The enhancement of the dolomite + illite component in recent years might indicate dominant sediment provenance from east in the Victoria Island/McKenzie River basin. IIlite was identified as an appropriate water mass tracer for a reverse flow from the Arctic into the North Pacific because of its prominence and abundance in the Mackenzie Rive (open full item for complete abstract)

Committee: Joseph Ortiz PHD (Advisor); Alison Smith PHD (Committee Member); Anne Jefferson PHD (Committee Member); Thomas Schmidlin PHD (Committee Member); John Dunlosky PHD (Committee Member) Subjects: Climate Change; Geology; Marine Geology; Oceanography; Paleoclimate Science

Master of Science (MS), Wright State University, 2013, Earth and Environmental Sciences

Trace metals in the ocean are derived from natural and anthropogenic sources. Despite increased human impact on the marine environment and biological productivity of continental margins, trace metal studies in marine sediments have focused primarily on near-shore regions. I investigated 22 metals in sediments on the continental margin of the northwest Atlantic Ocean to calculate enrichment factors (EF) relative to upper continental crust and identify spatial variations with distance from shore and depth below the sediment-seawater interface. Metals were well correlated with Al, Fe, organic matter, or CaCO3. No clear trends in metal EFs with distance from shore were evident on a station by station basis, but consistent differences among regions of the continental margin were evident. Significant near-shore enrichment was observed. Enrichment was also evident for As, Hg, Mn, and Ni in sediments farther off-shore, suggesting the influence of human activities or hydrothermal vent emissions have enriched deep ocean sediments.

Committee: Chad Hammerschmidt Ph.D. (Advisor); Chad Hammerschmidt Ph.D. (Committee Chair); Carl Lamborg Ph.D. (Committee Member); William Fitzgerald Ph.D. (Committee Member) Subjects: Chemical Oceanography; Environmental Science; Oceanography

Doctor of Philosophy (PhD), Wright State University, 2012, Environmental Sciences PhD

Multiple cores from the Arctic were analyzed by XRF methods to determine the western Arctic lithostratigraphy as expressed in its geochemistry. In general, glacial and interglacial events have distinctly different chemistry. During glacial events, the sediments have elevated Ti, Fe, Rb, and Zr concentrations and depressed Sr and Mn concentrations. The opposite is true of the brown layers, where Ti, Fe, Rb and Zr are lower with higher levels of Mn and Sr. These data indicate that there are 18 chemically unique lithologic units (LUs) that exist among MIS-1 to MIS-16 age sediments. Isopach maps indicate two general depositional patterns appear to have existed during the late Quaternary. The first pattern is defined as a glacial depositional pattern based on sediment thicknesses present in Clark et al. (1980) SLUs F, H, J, and L. This pattern has the thickest deposits located on parts of the Northwind-Alpha Ridges as well as within the Makarov Basin. The second pattern is associated with interglacial deposits and is based on sediment thicknesses present in SLUs G, I, and K. The interglacial pattern is characterized by much thinner deposits especially for the central Arctic region. Based on the isopach sediment patterns, the potential source areas of the sediments deposited during the glacial and interglacial periods are slightly different. During glacial stages, a strong Canadian source area is suggested. During interglacial stages a Canadian source area exists for deposits in the Canadian Basin, and a potential mixture of Canadian and Russian source areas for sediments located along the Trans-Polar Drift between the Mendeleev-Lomonosov Ridges. Stratigraphic correlations indicate that the western Arctic, central Lomonosov Ridge, and eastern Arctic are geochemically different suggesting different sources for each area. Analysis of the coarse ice-rafted fraction (>250 μm) from strata associated with MIS-16 (LU-17) indicates a Canadian source for the carbonate grains in th (open full item for complete abstract)

Committee: Steve Higgins PhD (Committee Chair); Dennis Darby PhD (Committee Co-Chair); Leonid Polyak PhD (Committee Member); Thaddeus Tarpey PhD (Committee Member) Subjects: Oceanography

Master of Science (MS), Wright State University, 2010, Earth and Environmental Sciences

Monomethylmercury (MMHg) is the toxic form of mercury (Hg) that biomagnifies in food webs, and human exposure to MMHg occurs predominantly via consumption of fish. The primary source of MMHg to the marine environment is thought to be in situ sedimentary production by benthic microorganisms, namely sulfate-reducing bacteria (SRB). I collected sediments from the continental shelf (stations 2 and 6) and slope (station 9) of the NW Atlantic Ocean, and amended them with various inhibitor and promoter solutions to target specific functional groups capable of Hg transformations. I also added stable enriched Hg isotopes to quantify gross Hg methylation and gross MMHg demethylation, which were detected with inductively couple plasma mass spectrometry (ICPMS). Hg isotope results suggest that biotic methylation accounted for at least 60% of gross Hg methylation and 0-40% of gross MMHg demethylation. Methanogens probably did not have a major role in MMHg production or demethylation at any of the stations. Iron-reducers (FeRB) were not primary Hg methylators, but iron-reduction (via a Fenton-like reaction) or Fe(III) limitation appear to have influenced MMHg demethylation. Nitrogen cyclers possibly were important in Hg methylation and MMHg demethylation may have been limited by nitrate. SRB were likely important producers of MMHg in nearly all of the sediments. Results of this study support previous research that SRB are important Hg methylators in sulfate-rich, marine environments. This study also highlights the potential importance of iron and nitrogen cycling in MMHg demethylation in marine sediments.

Committee: Chad Hammerschmidt Ph. D. (Committee Chair); Amy Burgin Ph. D. (Committee Member); William Fitzgerald Ph. D. (Committee Member) Subjects: Analytical Chemistry; Biogeochemistry; Chemistry; Environmental Science; Microbiology; Oceanography

Bachelor of Science (BS), Ohio University, 2010, Chemistry

The human health threat from marine algal toxins is increasing with expanding human population, increased seaside populations, and the concomitant increase in aquaculture operations and demand for seafood. As humans increase demand for seafood, they create waste and activity that may increase the likelihood of harmful algal blooms (HABs) and phycotoxin production by some of these blooms, notably the production of the causative toxins for ciguatera fish poisoning (CFP), paralytic shellfish poisoning (PSP), amnesic shellfish poisoning (ASP), neurotoxic shellfish poisoning (NSP) and diarrhretic shellfish poisoning (DSP). The mainstay for regulatory detection of these toxins has long been the mouse bioassay (MBA), with intraperitoneal (i.p.) injection of suspect extracts and subsequent monitoring for symptoms and time of death. The general sentiment in the research community is that there is a need to eliminate, or at least reduce, the use of the mouse bioassay in testing for algal toxins, due to technical limitations of the procedure and its ethical drawbacks. A number of functional and analytical methods have been developed to this end. This paper reviews the rise of harmful algal blooms, toxin syndromes, historical use of and the subsequent need to find an alternative to the mouse bioassay in detection of algal toxins and obstacles to the development of these alternative methods. The role of large importing countries in this process is then considered; particular attention is paid to the United States, as there is little discussion of their efforts in the literature.

Committee: Hao Chen (Advisor) Subjects: Biochemistry; Chemistry; Environmental Science; Oceanography; Toxicology