Master of Science (MS), Bowling Green State University, 2018, Geology

The southernmost volcanoes on Earth, Mt. Early and Sheridan Bluff, are two basaltic monogenetic volcanoes located 87°S at the head of the Scott Glacier, in the southern Transantarctic Mountains. The Early Miocene volcanoes lie ~1000 km from any other volcano and ~200 km from the shoulder of the West Antarctic Rift System (WARS), which is the foci of most Cenozoic alkaline volcanism in Antarctica. WARS is part of a larger diffuse alkaline magmatic province (DAMP) including volcanism in New Zealand and Australia. Dating by the 40Ar/39Ar method indicates that Mt. Early is older than previously determined and closer in age to Sheridan Bluff (~19 Ma). Basalts range in composition from alkaline (~6 wt. % Ne-normative) to subalkaline tholeiite (~6 wt. % Hy-normative). Tholeiite have higher ratios of Zr/Nb (9) than alkaline basalts (4) and have lower ratios of La/Yb (5), La/Lu (<50), and Gd/Yb (2) than alkaline basalts (20, 100-150, and ~3 respectively). Fractional crystallization, assimilation-fractional crystallization (AFC), and partial melting are tested as mechanisms to explain compositional variations. Crystal fractionation alone cannot explain the difference in composition. Modelling AFC on plots of Rb, Ba, and La/Nd versus TiO2 show that unrealistic bulk partition coefficients are required to explain the array of compositions using contaminates from the upper crust. I conclude that the coexistence of tholeiite and alkaline basalt is likely due to different degrees of partial melting. The basalts mirror partial melting trends for a common garnet lherzolite source on plots of La/Lu versus Nb/Yb. These models also suggest that tholeiite was produced by higher degrees of melting at shallower depths. Mt. Early and Sheridan Bluff basalt, especially tholeiite, are distinctive from DAMP basalt, having lower Ce/Pb (≤ 20), Gd/Yb (≤ 3) and lack K and Pb anomalies on normalized multi-element plots. Negative K anomalies are a prominent feature of DAMP basalt and are used to (open full item for complete abstract)

Committee: Kurt Panter Dr. (Advisor); Peter Gorsevski Dr. (Committee Member); Daniel Kelley Dr. (Committee Member) Subjects: Geochemistry; Geology; Petrology

Doctor of Philosophy, The Ohio State University, 2014, Atmospheric Sciences

The Antarctic Ice Sheet holds a volume of ice and snow equivalent to 55 meters of sea level. The melting of only a relatively small fraction of this volume could have dramatic consequences for populations around the world. With this in mind, the research presented here focuses on two atmospheric variables that are key controls of the state of the ice sheet: its surface mass balance (or net snowfall) and its near-surface air temperature. The analysis aims to understand how these two parameters have changed (if at all) since the 1957-1958 International Geophysical Year (IGY), the start of the instrumental era in Antarctica. Particular attention is given to the part of the continent known as West Antarctica, the most vulnerable to atmospheric and oceanic warming, and the one where rapid glacial change is currently taking place. The research is divided into three parts. The first part uses a set of seven global reanalyses to investigate the changes in Antarctic surface mass balance and Southern Ocean precipitation since 1979 (start of the reanalyses). This investigation is also intended to shed light on the reliability of these reanalyses, which often contained artifacts caused by changes in the observing system, particularly in high southern latitudes. Spurious changes in precipitation are found to various degrees in all data sets but with varying characteristics and origins. According to the two reanalyses deemed most reliable, neither Antarctic surface mass balance nor Southern Ocean precipitation have changed significantly over the past three decades. The second part consists of a multifaceted investigation of the near-surface temperature record from Byrd Station, in central West Antarctica. As the only meteorological record in this region to extend back to the IGY, it is a critical data set, but also one with a complicated history and substantial data gaps. A comprehensive revision of the record is undertaken and a novel approach is used to estimate the missi (open full item for complete abstract)

Committee: David Bromwich PhD (Advisor); Jay Hobgood PhD (Committee Member); Jeffrey Rogers PhD (Committee Member); Jialin Lin PhD (Committee Member) Subjects: Atmospheric Sciences; Climate Change

Doctor of Philosophy, The Ohio State University, 2023, Earth Sciences

Ice shelves regulate ice sheet contribution to sea level rise by buttressing ice flow. Many ice shelves around Antarctica are thinning and retreating, with the most significant changes occurring in West Antarctica. Many factors influence ice shelf stability, including changes at the grounding line, basal melt, stress transfer, and the incidence and advection of surface and basal features. The work presented in this dissertation elucidates connections between narrow ice shelf melt features (basal channels) and structural changes on ice shelves and challenges the assumptions used to examine ice shelf change. Chapter 2 presents work published in the Journal of Geophysical Research: Earth Surface (Chartrand & Howat, 2020). Here, we use high spatiotemporal-resolution digital surface models (DSMs) from the Reference Elevation Model of Antarctica (REMA), satellite laser altimetry, and airborne laser and radar altimetry to track the position of a basal channel on the Getz Ice Shelf and to quantify thickness changes and basal melt rates. We show that the basal channel incised at rates up to 22 m a-1 and migrated independently of ice flow at rates of 70-80 m a-1. Lastly, we show that parts of the basal channel are not freely floating, which reduces confidence in the assumption of hydrostatic equilibrium. These results provide new insights into basal channel evolution, demonstrate the value of REMA DSMs in examining ice shelf change, and inspired the work in subsequent chapters. In Chapter 3, we explore the implications of assuming hydrostatic equilibrium to estimate ice shelf thickness from surface height measurements. We compare hydrostatic ice thickness estimates from airborne surface height measurements with contemporaneous ice thickness measurements. We find that the hydrostatic thickness overestimates ice thickness by an average of 17 m, with significant variability at multiple spatial scales. We show that the hydrostatic thickness is highly sensitive to which corr (open full item for complete abstract)

Committee: Ian Howat (Advisor); W. Ashley Griffith (Committee Member); Joachim Moortgat (Committee Member); Michael Durand (Committee Member) Subjects: Earth; Geophysics

Master of Science (MS), Ohio University, 2023, Geography (Arts and Sciences)

As climate change continues unabated, understanding Earth's complex climate system remains critical. The Antarctic climate system is a crucial part of this system, and the sea ice surrounding the continent is an incredibly important element. With the largest change in albedo on Earth, Antarctic sea ice is responsible for reflecting solar radiation from the region. As seen in the Arctic as a result of climate change, without sea ice this solar radiation is absorbed by the low albedo ocean causing warming and further melt of sea ice in a positive feedback loop. Antarctic sea has not responded in the same way as the Arctic. Observations of Antarctic sea ice date back to October 1978 and have shown an overall increase in sea ice. A sudden decline in sea ice extent in 2016 was an unexpected turn of events, and a new record low extent in February 2023 has further complicated this. Due to the short records of Antarctic sea ice extent and the complex nature of the regional climate system, it is difficult to isolate the impacts of climate change in the region. To expand these short records, reconstructions have been utilized. Monthly reconstructions, based on observational temperature and pressure data, were created in order to extend this record to 1957. These reconstructions were analyzed in this study in order to determine their skill and understand how Antarctic sea ice extent has changed through the 1957-2020 period. This was done for the total sea ice extent around the Antarctic continent as well as the Bellingshausen-Amundsen, East Antarctic, King Hakon, Ross, and Weddell regions. The reconstructions were analyzed using correlation, regression, and comparison of means statistical methods in order to evaluate relationships between Antarctic climate data and sea ice extent, relationships between modes of climate variability and sea ice extent, changes in the seasonal cycle of sea ice extent, and trends in sea ice extent. It was of interest to det (open full item for complete abstract)

Committee: Ryan Fogt (Advisor); James Dyer (Committee Member); Timothy Anderson (Committee Member) Subjects: Atmospheric Sciences; Geography

Master of Science (MS), Ohio University, 2023, Geography (Arts and Sciences)

Changes in Earth's cryosphere, including sea ice in both polar regions, often result in amplified climate-related impacts through positive feedback loops, making it crucial to understand how and why the cryosphere is evolving now and into the future. Observations of Antarctic sea ice are comparably short as the records have only been reliably observed since the satellite era began in 1979. Prior to the satellite era, limited data sources on Antarctic sea ice are available, including various reconstructions and discrete information in ship logbooks from expeditions and commercial vessels written in the remarks sections. This research aims to further understand how independent early sources of information can be used to evaluate the skill of seasonal Antarctic sea ice extent reconstructions (Fogt et al. 2022). Ship logbook observations of sea ice are extremely valuable because they are able to give insight into where the ice edge was prior to satellite measurement in 1979. As this is a new area of research, little is yet known on what potential data have been recovered. Not only is it important to know what data are available, but also if the ship logbooks are reliable enough to be used to evaluate Antarctic sea ice extent reconstructions. This research compiled a list of available ship logbooks at Ohio University, only a handful of which were able to be digitized in time for this project. The latitudes from the ship logbooks of the ice edge show to be within an acceptable range of the latitudes of the sea ice from reconstructions (on average within 3°), indicating the skill of the sea ice extent reconstructions, spatially and temporally, is good prior to 1979. The Antarctic sea ice extent reconstructions were also compared with estimates of early twentieth century sea ice extent from coupled climate models in terms of the ranges of variability and linear trends. Overall, the variability in the sea ice, both temporally and spatially, are sim (open full item for complete abstract)

Committee: Ryan Fogt (Advisor); Geoffrey Buckley (Committee Member); Timothy Anderson (Committee Member) Subjects: Atmospheric Sciences; Climate Change

Master of Science (MS), Ohio University, 2022, Geography (Arts and Sciences)

Ongoing changes in the Earth's cryosphere create positive feedback loops through changing albedo, creating a spark of interest in researchers on what is happening in regions of sea ice. Despite this conviction for research, Antarctic sea ice observations have been sparsely recorded throughout human history and have only been reliably observed since the introduction of satellite measurements in approximately 1979. Recent research has shown the ability to reconstruct Antarctic pressure and sea ice extent values throughout two different studies using principal component regression techniques based primarily on temperature and pressure observations along with large-scale climate variability indices that influences Antarctic sea ice. This short historical span of sea ice concentration (SIC), a pixel-scale observation that outlines how much of the ocean area is covered in sea ice, have shown increases around much of Antarctica since 1979. This short historical record, comparatively, does not capture the full range of climate variability in one of the most isolated places on Earth. To improve the understanding of historical variations in Antarctic SIC, reconstructions of the five leading empirical orthogonal functions (EOF) have been conducted in this study to extend SIC data back to 1905. This new seasonally resolved dataset allows researchers to place current trends in a longer historical context. This study examines the skill of these seasonal Antarctic SIC reconstructions, the first of their kind, along with discussing regional changes in Antarctic sea ice since the beginning of the 20th century, and the implications these historical variations may have for further Antarctic sea ice and future research. The resultant reconstructions of SIC presented through this study outline the ability to gather skillful and meaningful results on seasonal scales through 1905 that provide overall much better skill than the climatological mean. These reconstructions allowed for a (open full item for complete abstract)

Committee: Ryan Fogt (Advisor); James Dyer (Committee Member); Jana Houser (Committee Member) Subjects: Atmospheric Sciences; Geography

Master of Science, Miami University, 2022, Microbiology

Ecosystems contain a variety of components that each need to be understood to get a complete picture of environmental change. Recently, fungi have become a rising point of interest in aquatic communities, as they have been shown to play roles akin to their soil bound counterparts. Here we explore which fungi may survive in Antarctic lakes in the McMurdo Dry Valleys and what roles these organisms may be performing in this unique ecosystem. We found that early-diverging lineage fungi, such as Cryptomycota, were common in the waters, and performing parasitic roles. Other fungal phyla, such as Ascomycota and Basidiomycota, were also found in higher abundance than previously predicted. In network analysis these unexpected fungi were shown to correlate with several chlorophyll producing organisms. Cryptomycota was found to correlate more with heterotrophic protists. Seasonal analysis showed that the fungal community was dynamic throughout the year, with the winter being heavily dominated by Cryptomycota. Our data suggests that fungi are dynamic players in the McMurdo Dry Valley ecosystem and are participating in several different roles.

Committee: Rachael Morgan-Kiss (Advisor); Annette Bollmann (Committee Member) Subjects: Biology; Ecology; Microbiology

Master of Science, The Ohio State University, 2021, Earth Sciences

The shape, size, chemistry, mineralogy, and number of atmospheric nano- and micro-particles all affect the amount of solar radiation reaching Earth's surface, and thus affect Earth's climate. While there have been measurements of individual particles larger than 200 nm in polar ice cores, to date, there have been very few measurements of individual particles less than 200 nm in polar ice cores, due to limitations of the analytical techniques used. This study serves as an initial investigation to document the physical and chemical characteristics of ancient particles entrapped in Antarctic ice, where the focus is heavily on method development. Fifty-seven individual particles, contained within two Antarctic ice core sections, have been measured using Transmission Electron Microscopy. The samples, dating to the Last Glacial Period at ~32 ky BP and Holocene at 9.5 ky BP, mark two distinct periods of Earth's climate and ice coverage. These two distinct periods in Earth's history affect both the source regions and transportation of particles in the atmosphere, which in turn affects the shape, size, chemistry, mineralogy, and number of particles measured. Previous measurements of the bulk trace element composition and Coulter Counter measurements of particle size distributions in melted ice core samples show that the chemistry and number of particles in the Last Glacial Period and the Holocene are quite different. We see no notable difference between shape, size, chemistry, and minerology between these two samples, although the number of measured particles (n = 57) may be too small to see any subtle differences. Eighty-five percent of the particles measured were smaller than 600 nm and would not have been detected by Coulter Counter which has been the most widely used technique to measure size distributions of particles in ice cores in the past. Sixty-seven percent of the particles measured were smaller than 200 nm, where this study serves as one of the first to sho (open full item for complete abstract)

Committee: John Olesik (Advisor); Paolo Gabrielli (Committee Member); Berry Lyons (Committee Member); Tomas Darrah (Committee Member) Subjects: Geochemistry

Master of Science (MS), Wright State University, 2021, Earth and Environmental Sciences

The cumulative number versus floe area distribution of seasonal ice floes from four satellite images covering the Summer season (November - February) in the Weddell Sea Antarctica during the summer breakup and melting is fit by two scale-invariant power scaling regimes for the floe areas ranging from 7 to 20 x 108 m2. Scaling exponents, β, for larger floe areas range from -1.5 to -1.7 with an average of -1.6 for floe areas ranging from 6 x 106 to 55 x 107 m2. Scaling exponents, β, for smaller floe areas range from -0.8 to -0.9 with an average of -0.85 for floe areas ranging from 3 x 106 to 1.55 x 106 m2. The inflection point between the two scaling regimes ranges from 62 x 106 to 151 x 106 m2 and generally moves from larger to smaller floe areas through the summer season. We propose that the two power scaling regimes and the inflection between them are defined during the initial breakup of sea ice solely by the process of fracturing. The distributions of floe size regimes retain their scaling exponents as the floe pack evolves from larger to smaller floe areas from the initial breakup through the summer season, due to scale-independent processes including grinding, crushing, fracture, and melting. The scaling exponents for floe area distribution are in the same range as those reported in previous studies of Antarctic and Arctic floes. A probabilistic model of fragmentation is presented that generates a single power scaling distribution of fragment size.

Committee: Christopher Barton Ph.D. (Advisor); Sarah Tebbens Ph.D. (Committee Member); Doyle Watts Ph.D. (Committee Member) Subjects: Earth; Remote Sensing

Master of Science (MS), Ohio University, 2021, Geography (Arts and Sciences)

Due to the global impacts of Antarctic sea ice and the changing climate, it is important to understand what is influencing Antarctic sea ice variability in a historical context. This is especially true since observations of Antarctic sea ice only begin around 1979. To investigate what is influencing Antarctic sea ice in a longer context, this study generated, evaluated, and analyzed new reconstructions of Antarctic sea ice extent (SIE) through statistical relationships with other long-term datasets available throughout the 20th century. A principal component regression technique that has been proven successful in other Antarctic climate reconstructions was employed in this study, using pressure and temperature observations across the Southern Hemisphere in conjunction with indices of large-scale climate variability known to influence Antarctic SIE. Ultimately, this study was conducted to determine if Antarctic SIE reconstructions are a skillful measure for understanding historical Antarctic sea ice trends and variability throughout the 20th century. The newly generated reconstructions demonstrate that skillful seasonal (extending back to 1905) and monthly (extending back to 1957) sea ice reconstructions can be produced. In comparison, the monthly reconstructions outperformed the seasonal reconstructions based on various assessments (including an independent validation approach), although both sets of reconstructions improved historical sea ice extent knowledge well beyond the use climatological mean. Although shorter in duration due to the inclusion of nearby Antarctic temperature and pressure (which begin near 1957), the monthly reconstructions also allowed for a broader analysis on sea ice extent for month-to-month variations and were useful for monitoring changes in the reconstruction skill performance that could not be seen on a seasonal level. While these new reconstructions unlock new information previously unknown about early 20th century Antarctic sea ice e (open full item for complete abstract)

Committee: Ryan Fogt (Advisor); Jana Houser (Committee Member); Gaurav Sinha (Committee Member) Subjects: Atmospheric Sciences; Climate Change; Earth; Environmental Science; Geography; Meteorology; Physical Geography

Doctor of Philosophy, The Ohio State University, 2020, Geodetic Science

Quantitative assessment of the mass balance of polar ice sheets plays an important role in better understanding the response of ice sheets to anthropogenic climate change, the present-day and future global sea level change, and interactions between the ice sheets and the atmosphere, ocean and the solid Earth. In this study, I investigate the mass balance of Greenland and Antarctica ice sheets using Gravity Recovery And Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) twin-satellite missions gravity data from April 2002 to August 2020. Auxiliary gravity data from the Swarm mission 3-satellite constellation are also used to support the analysis bridging the GRACE/GRACE-FO data gap (July 2017 to May 2018). Ensemble models are composed combining the official GRACE temporal gravity solutions from CSR, GFZ, JPL and the in-house developed GRACE models using the improved energy balance approach (EBA). The improved atmospheric de-aliasing data produced using the ECMWF (European Centre for Medium-Range Weather Forecasts) Reanalysis 5th Generation (ERA5) data product, and 3-dimensional atmosphere mass computational algorithms are collectively used. The Swarm gravity models are also ensemble of four solutions produced from the kinematic orbit data using four different gravity recovery methods. Post-processing of the gravity models includes replacing low degree spherical harmonic terms (geocenter motions, J2 and J3), destriping filtering, Gaussian smoothing, glacial isostatic adjustment (GIA), forward modeling based signal leakage reduction and ellipsoidal correction. The satellite gravimetric data show that during the period of 2002/04-2020/08, Greenland and Antarctica ice sheets experience rapid mass losses at mean rates of -235.6±3.8 Gt/yr and -122.6±4.6 Gt/yr respectively, equivalent to 0.65 mm/yr and 0.34 mm/yr global sea level changes. In spatial domain, the southern part (including southeast and southwest regions) of Greenland contributes 52.3% of the total Green (open full item for complete abstract)

Committee: C.K. Shum (Advisor); Michael Bevis (Committee Member); Howat Ian (Committee Member); Wei Feng (Committee Member) Subjects: Climate Change; Earth; Geophysics

Doctor of Philosophy, The Ohio State University, 2020, Geodetic Science

The temporal gravity solutions estimated from NASA/DLR's Gravity Recovery And Climate Experiment (GRACE) mission, and its successor, NASA/GFZ's GRACE Follow-On (GRACE-FO), manifested as mass transports within the Earth system, have been used for a wide variety of Earth Science and climate change studies since 2002. However, there is an around one-year gap between the two satellite gravity missions (2017-2018). ESA's fifth Earth Explorer Mission, the Swarm 3-satellite constellation, equipped with geodetic quality GNSS tracking system, was proposed to fill the gravimetry observation climate record data gap, at a moderate spatial resolution. Here, I applied a modified decorrelated acceleration approach to recover temporal gravity field using the 3-satellite Swarm constellation GPS tracking data. This approach is based on the simple linear relation between the second time derivative of the orbit and the gravitational acceleration. However, the time derivative could highly amplify the noise and make the noise correlated. In addtion, GPS positioning also involves correlation noise. Therefore, two linear transformations were introduced to decorrelate the observation noise. Next, two adjustment methods were studied to optimally combine the three gravity components, namely along-track, cross-track, and radial direction, along with introducing relative weights among orbital arcs for the final optimal gravity field estimation. The Swarm-only temporal gravity solutions have a good to excellent agreement with the overlapping GRACE/GRACE-FO solutions at least up to spherical harmonics degree around 13 (~1500 km, half-wavelength). Swarm-only temporal gravity solutions were then used to fill the mass change data gap over Greenland and West Antarctica ice-sheets during 2017-2018. Over Greenland, Swarm observed mass anomalies agreed well within the time epochs that overlaped with GRACE (correlation coefficient (CC) = 0.62), and GRACE-FO (CC=0.78). Within the data gap year, Swarm ob (open full item for complete abstract)

Committee: C. K. Shum Dr. (Advisor); Michael Bevis Dr. (Committee Member); Ralph von Frese Dr. (Committee Member); Lei Wang Dr. (Committee Member); Dah-Ning Yuan Dr. (Committee Member) Subjects: Geophysical; Geophysics

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

Though the majority of the Antarctic continent is covered by ice, portions of Antarctica, mainly in the McMurdo Dry Valleys and the Transantarctic Mountains (TAM), are currently ice-free. The soils which have developed on these surfaces have been re-worked by the advance and retreat of glaciers since at least the Miocene. They are generally characterized by high salt concentrations, low amounts of organic carbon, and low soil moisture in a polar desert regime. Ecosystems that have developed in these soils have few taxa and simplistic dynamics, and can therefore help us understand how ecosystems structure and function following large-scale changes in climate, such as glacial advance and retreat. During the 2017-2018 austral summer, 220 surface soil samples and 25 depth profile samples were collected from eleven ice-free areas along the Shackleton Glacier, a major outlet glacier of the East Antarctic Ice Sheet. A subset of 27 samples were leached at a 1:5 soil to deionized (DI) water ratio and analyzed for stable isotopes of water-soluble NO3- (δ15N and Δ17O) and SO42- (δ34S and δ18O), and seven soils were analyzed for δ13C and δ18O of HCO3 + CO3 to understand the sources and cycling of salts in TAM soils. The depth profiles and a subset of surface soil (21) samples were analyzed for concentrations of meteoric 10Be and/or water-soluble NO¬3- to estimate relative surface exposure ages along the length of the Shackleton Glacier. Finally, water-soluble ion data from all 220 samples were correlated with geography and geomorphology to elucidate geochemical trends and gradients. The relationship between geochemistry and geography was further used to predict/estimate geochemical gradients in the TAM using interpolation and machine learning techniques. Collectively, these measurements and data show that atmospheric deposition is an important source of water-soluble anions, which have possibly been accumulating in some soils since at least the Pleistocene. Soils near the termi (open full item for complete abstract)

Committee: W. Berry Lyons PhD (Advisor); Thomas Darrah PhD (Committee Member); Elizabeth Griffith PhD (Committee Member); Bryan Mark PhD (Committee Member) Subjects: Earth; Geochemistry; Geography; Geological

Master of Science (MS), Bowling Green State University, 2020, Geology

Mt. Early and Sheridan Bluff are two Miocene volcanoes located near 87°S in the southern Transantarctic Mountains on the East Antarctic craton, ~1000 km away from any other exposed Cenozoic volcano associated with the West Antarctic Rift System (WARS). The basalts are unique in comparison with WARS, in that subalkaline (tholeiite) to alkaline (hawaiite and mugearite) magmas were nearly simultaneously generated during the Early Miocene (20 to 19 Ma). Close examination of isotopic measurements provide insight into mantle sources and cause of melting beneath the East Antarctic craton. Enriched isotopic signatures such as mildly elevated δ18O in olivine (average =5.55 ± 0.19 ‰) and whole rock 87Sr/86Sr ratios (0.7038-0.7049) indicate contamination by crustal material. However, the correlations between isotopes and major and trace elements (e.g. SiO2, MgO, Sr, and Zr) are either not seen or opposite of what would be expected for models for combined assimilation and fractional crystallization. Alternatively, the higher Sr and O and lower Nd and Pb isotopic values of Mt. Early and Sheridan Bluff samples compared to WARS basalts likely reflect crustal material within their mantle source (e.g., an EMII-like component). The isotopic variations shown by alkaline and tholeiitic basalts could be explained by different degrees of partial melting of a heterogeneous mantle containing crustal materials. Possible mechanisms to add crust is lithospheric delamination which occurred beneath this portion of the Transantarctic Mountains or recycled by past subduction zone processes.

Committee: Kurt Panter Ph.D. (Advisor); John Farver Ph.D. (Committee Member); Peter Gorsevski Ph.D. (Committee Member) Subjects: Earth; Geochemistry; Geological; Geology

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

In recent decades, West Antarctica (WA) has undergone extensive surface warming mainly due to the large-scale atmospheric variability. The increasing summer surface air temperature can promote glacier acceleration and ultimately increase ice loss and sea-level rise. For areas like the Antarctic Peninsula (AP), surface melting triggered by temperature increase since the 1950s significantly contributes to the ice loss, such as the Larsen B ice shelf collapse in 2002. Over ice shelves outside the AP, basal melting still dominates surface ice shelf thinning at present. However, with the current warming trend and substantial surface melting in WA projected by climate models, it is unclear if this projected surface melting will also lead to continental ice loss as it has and continues to do in the AP. With limited surface observations due to the extreme weather over Antarctica, our understanding of regional climate conditions in WA is not comprehensive. Previous studies assess the long-term temperature trend using model simulations (e.g. Bromwich et al., 2013b), but research on individual melt events and regional factors is limited. Thus, this study: 1) investigates the 2016 melt case based on Antarctic Mesoscale Prediction System (AMPS) outputs; 2) improves the Polar WRF (PWRF) simulation results by using high-resolution reanalysis data as input fields, surface albedo from satellite observations, and better selection of physical schemes; 3) analyzes and quantifies the contributors of surface melting in four previous major melt cases based on improved model simulations. This research is intended to understand the physical mechanisms of surface melting and to distinguish the contribution of each factor, which can benefit future projections of the stability of the Ross Ice Shelf (RIS) as a result of a changing climate. This study first investigates the foehn effect at the beginning of the 2016 event via the AMPS output. The foehn effect increases surface temperature by up (open full item for complete abstract)

Committee: David Bromwich Dr. (Advisor); Alvaro Montenegro Dr. (Advisor); Ellen Mosley-Thompson Dr. (Committee Member); Jay Hobgood Dr. (Committee Member) Subjects: Atmospheric Sciences

Master of Science (MS), Ohio University, 2020, Geography (Arts and Sciences)

Atmospheric circulation patterns and additional external forcings create strong connections across the entire Southern Hemisphere, specifically between the mid- and high-latitudes. These relationships have made it possible to reconstruct surface pressure over Antarctica, extending records back to the beginning of the 20th century. This is accomplished by using station data from southern midlatitude locations and performing Principal Component Regression (PCR) in order to predict pressure records over Antarctica prior to readily available observations in 1957. This study evaluates PCR reconstructions created from observations compared to reconstructions created in the Community Atmospheric version 5 (CAM5) model. These pressure datasets will now span from 1905 – 2013, and by using CAM5, supplementary tests can be made on the notion of the stationarity constraint. Reconstruction performance remained high across all datasets, with CAM5 model skill exceeding the observational reconstructions in every season except for the austral summer. This held true even when switching the calibration period in the model from 1957 – 2013 to 1905 – 1956, which is the time period used to establish relationships across the full reconstruction period. A number of tests on the stationarity constraint found that stability in the model remained fairly persistent across the full time period, with West Antarctica sharing stronger connections to the southern midlatitudes. When evaluating century-length reanalyses to the CAM5 model, it was found that these reanalysis products have varying relationships with the southern midlatitudes through time that disrupts stability and compromises global mass conservation laws. Nonetheless, the new reconstructed pressure datasets are deemed to be reliable estimates of Antarctica pressure variability since the beginning of the 20th century. These data provide meaningful results, and are an additional tool that can be used to understand long-term climate vari (open full item for complete abstract)

Committee: Ryan Fogt (Advisor); Jana Houser (Committee Member); James Dyer (Committee Member) Subjects: Climate Change; Meteorology

Doctor of Philosophy, University of Akron, 2019, Chemical Engineering

Breast Cancer is the most common cancer among women and nearly 1 in every 8 American women suffer from it. Triple negative breast cancer, a type of breast cancer that can be only treated using chemotherapy, affects nearly 20% of the breast cancer diagnosed women. Early detection of breast cancer increases survival rates among patients. This dissertation discusses the development of a new two-functional folate-targeted poly(ethylene glycol)-based fluorescein-labeled conjugate (FA-FL-PEG-FL-FA) for potential applications in selective diagnosis of triple negative breast cancer. Since folate, or vitamin B9, receptors (FRs) are overexpressed in breast cancer cells, the diagnosis of these cells is targeted by using a γ-thiolated folic acid (FA-γ-SH) as the targeting precursor. α-carboxyl group present on folate is necessary for binding with the FRs, therefore, exclusive γ-thiolation was achieved by using n-butyllithium that selectively forms the lithium salt (FA-γ-Li) at the γ-carboxyl position due to its higher pKa. The subsequent thiolation was achieved by reducing FA-γ-S-S-γ-FA, which was prepared by reacting a dibrominated disulphide compound (Br-S-S-Br, synthesized via enzyme-catalyzed transesterification) with FA-γ-Li. To increase the retention time in the body and improve the solubility of the agent in water, functionalized PEGs were used as the hydrophilic linkers. Diamine, dithiol, and dibromide functionalization of PEGs were achieved using novel enzyme (Candida antartica Lipase B)-catalyzed esterifications and transesterifications. Specifically, three strategies to synthesize FA-FL-PEG-FL-FA were investigated for their synthetic convenience and feasibility. Strategy 1 used diamine-functionalized PEG (H2N-PEG-NH2), Strategy 2 used dithiol-functionalized PEG (HS-PEG-SH), and Strategy 3 used dibromide-functionalized PEG (Br-PEG-Br) as the precursors. The first strategy and the third strategy were not successful owing to not quantitatively yielding the interm (open full item for complete abstract)

Committee: Lingyun Liu (Advisor); Jie Zheng (Committee Member); Rebecca Kuntz Willits (Committee Member); Chrys Wesdemiotis (Committee Member); Mark Soucek (Committee Member) Subjects: Chemical Engineering; Chemistry; Molecules; Organic Chemistry; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2019, Chemical Engineering

The aim of this research was to synthesize polymer-diagnostic agent conjugates with two folate functionalities for potential diagnostic applications. Conjugates with fluorescein (FL) as an imaging agent, poly(ethylene glycol) (PEG) as a hydrophilic linker and two folic acid (FA) as targeting agents were synthesized by chemo-enzymatic method using Candida antarctica lipase B (CALB) catalyst for the multivalent targeting of folate receptors (FRs) overexpressed on cancer cells. In this dissertation work, imaging agent FL was first acrylated using acryloyl chloride (AcrCl) in the presence of triethylamine (TEA) to precisely synthesize fluorescein o-acrylate (FL-A, yield: 52.49%) and fluorescein o,o'-diacrylate (FL-DA, yield: 63.9%). A kinetic study of FL-DA synthesis was conducted using a Nuclear Magnetic Resonance (NMR)-750 MHz spectrophotometer instrument which demonstrated the formation FL-DA in 13 seconds reaction time. Hence, our FL-DA synthesis was extremely fast and easy to purify using silica gel. Acrylate moieties of FL-DA and FL-A allow the CALB-catalyzed Michael addition of thiol and amine to develop the conjugates. First, FL-A with single acrylate moiety was reacted with PEG-diamine (H2N-PEG-NH2) by the CALB-catalyzed Michael addition. However, the nucleophilic secondary amine of FL-NH-PEG-NH-FL interfered with the acrylation of 'OH' of FL-A. Hence, a new synthetic strategy was developed where H2N-PEG-NH2 was replaced by dithiol-functionalized PEG (HS-PEG-SH, Mn =899 g/mol, Ð=1.00, Mn =1160 g/mol, Ð=1.14 and Mn =2200 g/mol, Ð=1.09) and tetraethylene glycol (HS-TEG-SH, FW= 370.48 g/mol) which were synthesized in Dr. Puskas' lab to avoid the interference of the amine group in the acrylation reaction. Michael addition between FL-A and HS-TEG-SH, by CALB-catalysis was extremely fast and completed in 1 minute at 52°C. Reaction between FL-A and HS-PEG-SH without CALB catalysis did not go to completion even after 18 hours at 52°C but completed in 2 minutes when C (open full item for complete abstract)

Committee: Jie Zheng PhD (Advisor); Ge Zhang PhD (Committee Member); Chrys Wesdemiotis PhD (Committee Member); Bi-min Zhang Newby PhD (Committee Member); Mark Soucek PhD (Committee Member) Subjects: Biomedical Engineering; Chemical Engineering; Chemistry; Materials Science; Polymer Chemistry; Polymers

Master of Sciences, Case Western Reserve University, 2020, Geological Sciences

Glassy spherules from three Transantarctic Mountain sediments were geochemically analyzed and at two of these sites (Mt. Raymond (RY) in the Grosvenor Mountains and Meteorite Moraine (MM) in Walcott Neve, in the Beardmore Glacier region of Antarctica) Australasian microtektites were discovered. The microtektites were identified based on their pale yellow appearance and confirmed geochemically; they have high concentrations of silica (SiO2 = 60.0 +/- 6.9 wt%) and alumina (Al2O3 = 23.0 +/- 4.0 wt%) and all have K2O/Na2O > 1, characteristic of microtektites and distinct from spherules of meteoritic origin. Additionally, the trace element pattern matches the upper continental crust with enrichments in refractory elements and depletions in volatile elements, most likely as a result of melting and vaporization of the source material. The presence of Australasian microtektites in RY sediment confirms the recent Australasian strewnfield extension to Antarctica (Folco et al., 2008) and the presence of highly-depleted microtektites (Van Ginneken et al., 2018). In addition to microtektites, thousands of chondritic spherules and a few unique cosmic spherules were identified in RY, MM, and Jacobs Nunatak (JA) sediments. These sites are evidently successful cosmic dust and impact debris collectors, and thus their usefulness in recording influx events is explored.

Committee: Ralph Harvey Dr. (Committee Chair); James Van Orman Dr. (Committee Member); Steven Hauck II Dr. (Committee Member) Subjects: Geochemistry; Geology

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

Chapter 1: Lake Vostok is named for the nearby Vostok Station located at 78°28'S, 106°48'E and at an elevation of 3,488 m. The lake is covered by a glacier that is approximately 4 km thick and comprised of 4 different types of ice: meteoric, basal, type 1 accretion ice, and type 2 accretion ice. Six samples were derived from the glacial, basal, and accretion ice of the 5G ice core (depths of 2,149 m; 3,501 m; 3,520 m; 3,540 m; 3,569 m; and 3,585 m) and prepared through several processes. The RNA and DNA were extracted from ultracentrifugally concentrated meltwater samples. From the extracted RNA, cDNA was synthesized so the samples could be further manipulated. Both the cDNA and the DNA were amplified through polymerase chain reaction. Ion Torrent primers were attached to the DNA and cDNA and then prepared to be sequenced. Following sequencing the sequences were analyzed using BLAST. Python and Biopython were then used to collect more data and organize the data for manual curation and analysis. Chapter 2: As a result of the glacier and its geographic location, Lake Vostok is an extreme and unique environment that is often compared to Jupiter's ice-covered moon, Europa. Lake Vostok was originally thought to be sterile, but multiple studies have suggested that not only is there a variety of bacterial and eukaryotic organisms living in the lake, but it may contain a complex ecosystem. The results of this analysis yielded metagenomic and metatranscriptomic data that aligned with a wide variety of organisms from 30 different phyla. The associated organisms were capable of many metabolic pathways, such as the nitrogen cycle and carbon fixation, as well as oxidation and/or reduction pathways for sulfur, iron, arsenic, hydrogen, hydrocarbon, phosphorous, uranium, and chromium compounds. The number of organisms unique to each sample was quite high for all samples except the layered meteoric ice sample, which only contained sequences similar to one organism. These results, (open full item for complete abstract)

Committee: Scott Rogers Ph.D (Advisor); Helen Michaels Ph.D (Committee Member); Paul Morris Ph.D (Committee Member) Subjects: Bioinformatics; Biology; Microbiology; Molecular Biology; Paleoecology