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Nicolas, Julien PierreAtmospheric Change in Antarctica since the 1957-1958 International Geophysical Year
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 missing observations. The complete Byrd record reveals a marked increase in the annual mean temperature since the late 1950s. This warming is not only stronger than previously estimated by other studies, but also establishes central West Antarctica as one of the fastest-warming regions on Earth. A review of the atmospheric and oceanic drivers of the temperature trends highlights their strong seasonal dependence and the complex interplay between low-latitude sea surface temperature forcing and high-latitude atmospheric variability. The third and final part of the research builds upon the new Byrd record and the records from 14 other stations to generate an Antarctic-wide temperature reconstruction spanning the IGY to the present time. The spatial interpolation method is adapted from, and improves upon, a kriging technique previously employed for the same purpose. The reconstruction is then used to re-examine the relationship between the Southern Annular Mode (the dominant mode of high southern latitude atmospheric variability) and Antarctic temperatures. The analysis shows how the strengthening of the SAM in austral summer and fall seen in recent decades has mitigated an otherwise stronger background warming of Antarctica.

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

Keywords:

Antarctica; West Antarctica; reanalysis; surface mass balance; reconstruction; Byrd; ice sheet; climate change

Deuerling, Kelly M.Aeolian Sediments of the McMurdo Dry Valleys, Antarctica
Master of Science, The Ohio State University, 2010, Geological Sciences

The role of dust has become a topic of increasing interest in the interface between climate and geological/ecological sciences. Dust emitted from major sources, the majority of which are desert regions in the Northern Hemisphere, is transported via suspension in global wind systems and incorporated into the biogeochemical cycles of the ecosystems where it is ultimately deposited. While emissions within the McMurdo Dry Valleys (MDV) region of Antarctica are small compared to other source regions, the redistribution of new, reactive material by wind may be important to sustaining life in the ecosystem.

The interaction of the dry, warm foehn winds and the cool, moist coastal breezes “recycles” soil particles throughout the landscape. The bulk of sediment movement occurs during foehn events in the winter that redistribute material throughout the MDV. To understand the source and transfer of this material samples were collected early in the austral summer (November 2008) prior to the initiation of extensive ice melt from glacial and lake surfaces, aeolian landforms, and elevated sediment traps. These were preserved and processed for grain size distribution and major element composition at the sand and silt particle sizes. Major elemental oxide analysis indicated that the silt and sand size particles are of different composition: SiO2 values for silt range from 50 to 59% by weight and for sand range from 59 to 74%. When compared to the elemental oxide composition four rock types present in the MDV, the composition of the silt indicates a mixing influenced mostly by the igneous rock types (Ferrar Dolerite and McMurdo Volcanic basanite) and sand a mixing influenced largely by the sedimentary rocks (Beacon Sandstone and the metasedimentary Basement Complex). This could imply a local source of the aeolian material that is corroborated by low CIA values at both particle sizes (44-57%) indicating low degrees of chemical weathering. In addition, comparison of 87Sr/86Sr and 143Nd/144Nd to values published for the major MDV rock types and ice core dust to values analyzed in 3 silt size glacier sample and one bulk glacier sample also indicates a local source of sediments and that it is not likely to be transferred inland.

During the melt season, the aeolian material is actively solubilized where it interacts with water, releasing solutes and vital bioavailable nutrients throughout the aquatic system. Differences in the chemistry of supra- and proglacial streams as well as lake surface waters may be derived from the deposition and dissolution of these aeolian sediments. To simulate these conditions, a two-step leaching method using deionized water to represent glacial melt in field conditions was employed and leachates analyzed for major ion and nutrient constituents. Leachates represent a small degree (<0.7%) of dissolution of major elements, and are solubilized to a greater extent from samples closer to the coast or with increased silt content. The composition of the leachates reflects the dissolution of the major salts found in the MDV. Leach 1 (cold water) indicates that Na- and Cl-bearing salt phases are dissolved to a greater extent than seen in Leach 2 (freeze-thaw). Conversely, Leach 2 compositions indicate that carbonate mineral dissolution and Mg-bearing silicate weathering are proceeding to a greater extent than in Leach 1.

Inorganic N:P ratios follow the same patterns of nutrient limitations based on the Redfield Ratio found by Priscu (1995) in the terminal lakes of the Taylor Valley: N-limited in the Fryxell and Hoare basins (east) and P-limited in the Bonney basin (west). This is also consistent with the age of the tills in the area, as found by Gudding (2003). The concentration of soluble Fe in the leachates is about the same as soluble inorganic P, and thus is not a limiting nutrient in the leachates. Comparison of total dissolved N and P to their inorganic counterparts reveals increased organic nutrients in the glacier and lake leachates that may indicate the influence of biota. Nutrient fluxes based on known sediment fluxes from elevated sediment traps deployed throughout the MDV and the composition of these leachates range from 0.34-330 g a-1 for N, 0.02-8.3 g a-1 for P, and 0.03-8.6 g a-1 for Fe. These are at least two orders of magnitude less than calculated loads from streams to the lakes in the Taylor Valley and, thus, should be considered underestimations or minima.

This work provides the first investigation into the composition and source of aeolian transported materials in the MDV, as well of what is potentially solubilized from it during the austral summer melt season. In addition, it will contribute to the understanding of the interplay between aeolian and aquatic processes in the MDV and further the understanding of this unique ecosystem.

Committee:

W. Berry Lyons, PhD (Advisor); Michael Barton, PhD (Committee Member); Garry D. McKenzie, PhD (Committee Member)

Subjects:

Environmental Geology; Environmental Science; Geological; Geology; Geomorphology

Keywords:

dust; aeolian transport; experimental leaching; geochemistry; Antarctica; McMurdo Dry Valleys; sediment provenance;weathering

Antibus, Doug E.Molecular and Cultivation-based Characterization of Ancient Algal Mats from the McMurdo Dry Valleys, Antarctica
MS, Kent State University, 2009, College of Arts and Sciences / Department of Biological Sciences
The McMurdo Dry Valleys in Antarctica present an opportunity for viable bacteria and bacterial DNA to be preserved over millennial-scale periods of dormancy because 1) the cold and dry climate of the Dry Valleys favors preservation of biological materials and 2) many Antarctic microbes are adapted to withstand stresses resulting from long periods of dormancy. Because of this potential for microbial preservation, the Dry Valleys may be the recipients of a legacy of genetic diversity dating from the Holocene, when the valleys were occupied by glacial lakes, although this possibility has not been previously investigated.This study examined samples of algal mat from the McMurdo Dry Valleys representing a chronological sequence in 14C age from 8 to 26,539 years before present. Research focused on the recovery of bacterial DNA and the examination of bacterial diversity by bacterial 16S rRNA gene clone libraries, as well as the recovery of cultivable bacteria from the samples. Bulk DNA abundance, bacterial DNA integrity, and the abundance and diversity of cultivable bacteria all declined with increasing sample age, matching expected patterns for ancient materials. Clone sequences belonging to the Cyanobacteria were abundant in a modern sample but absent from ancient samples. In contrast, Firmicutes 16S rRNA gene sequences and cultivable Firmicutes were abundant in ancient samples. The abundance of Firmicutes supports the inference that bacterial gene sequences and cultivable bacteria from samples were authentically ancient, as Firmicutes are not common in Antarctic soils. Additionally, anaerobe sequences were abundant in clone libraries, which would be expected for Antarctic algal mats rather than mineral soils. BOX-PCR genotyping was applied to 105 isolates belonging to the Firmicutes genus Sporosarcina from ancient and modern samples. Previous research in the McMurdo Dry Valleys has found that highly similar 16S rRNA gene sequences are distributed throughout the landscape, suggesting that alpha and gamma richness of bacterial species are similar. In this study, little overlap of Sporosarcina genotypes between samples was observed, suggesting that gamma richness of genotypes is greater than alpha richness. Isolates displayed differential responses to growth temperature, which was associated with BOX-PCR genotype. Genotypes were also unevenly distributed over temperature and medium treatments used in initial cultivation attempts, suggesting that genotypes are adapted to different substrate and temperature conditions.

Committee:

Christopher Blackwood (Advisor); Laura Leff (Committee Member); Christopher Woolverton (Committee Member)

Subjects:

Biology

Keywords:

McMurdo Dry Valleys; Antarctica; microbial dormancy; ancient microbes

Juma, Sammy OgutiMetagenomic/Metatranscriptomic Study of Organisms Entrapped in Ice at Four Locations in Antarctica
Master of Science (MS), Bowling Green State University, 2013, Biological Sciences
Antarctica has one of the most extreme environments on Earth. The biodiversity and the species richness on the continent are low and decrease with increases in elevation and distance from the coastal regions. Previous scientific research in Antarctica has been used to understand the past climatic conditions, survival mechanisms used by the microbial communities and various environmental factors that contribute the dispersal of microorganisms. The research presented here is a comparison of microbial inclusions in ice at four locations in Antarctica (Byrd, Taylor Dome, Vostok and J-9) to identify the factors that influence the microbial distribution patterns and to investigate survival of the micobes under harsh conditions. Culture-dependent and culture independent techniques (e.g., metagenomics and metatranscriptomics) were used to analyze sequences present in ice cores from Antarctica. The sequences analyzed matched those from Spirochaetes, Verrucomicrobia, Bacteroideters, Cyanobacteria, Deinococcus-Thermus, Proteobacteria, Firmicutes, Actinobacteria, Euryarchaeota and Ascomycota. Analysis of the metagenomic/metatranscriptomic sequences was also carried out to characterize the various pathways represented in the diverse communities. Analysis of the data revealed that the numbers of unique sequences obtained from the samples were few (Taylor Dome (51), Byrd (43), Vostok (33) and J-9 (40). The number of unique sequences was lowest from the sample obtained at the most elevated location in the interior of Antarctica (Vostok (33)) and highest from the sample that was closest to the Antarctic coast (Taylor Dome (51)). The samples from all the four locations appeared to harbor very few species of microorganisms (Taylor Dome (12), Byrd (13), Vostok (6), and J-9 (7)). Analysis of the microbial pathways revealed that the microorganisms are able to utilize various sources of carbon, recycle nitrogen and had unique enzymes and cell structures that have previously been reported to be important for microbial survival at very low temperatures.

Committee:

Scott Rogers (Advisor); Paul Morris (Committee Member); Vipaporn Phuntumart (Committee Member)

Subjects:

Biology; Molecular Biology

Keywords:

Metagenomic; Metatranscriptomic; Antarctica; 454 Pyrosequencing

Krans, Susan RNew Mineral Chemistry and Oxygen Isotopes from Alkaline Basalts in the Northwest Ross Sea, Antarctica: Insights on Magma Genesis across Rifted Continental and Oceanic Lithosphere
Master of Science (MS), Bowling Green State University, 2013, Geology
The West Antarctic Rift system hosts one of the world's most extensive alkaline igneous provinces. Rifting that lead to the breakup of the proto-Pacific margin of Gondwana in the Late Cretaceous was initially amagmatic and not related to mantle plume activity. Mantle heterogeneities and magmatic processes along a continent-ocean transect in the Antarctic Northwest Ross Sea region are deduced from geochemical and isotopic study of alkaline basalts. Specifically, new mineral chemistry and oxygen isotopes from the least differentiated basalts expand upon previous studies that have focused primarily on whole-rock data. Alkali olivine basalt and basanite represent two mafic end-members in the Northwest Ross Sea and are characterized by high whole rock Mg# (59 ± 9), Ni + Cr (> 200 ppm), highly variable CIPW normative (> 20% hypersthene to > 20% nepheline) and trace element contents (e.g., Sr = 400 to 1100 ppm, La/Yb = 11 to 28, Nb/Y = 1.2 to 3.6). Phenocryst phases are primarily olivine (Fo66 to Fo91) and clinopyroxene (diopside) with rare amphibole (kaersutite) and exhibit varying degrees of compositional zoning. Temperature and pressure estimates based on mineral-liquid equilibrium range from 1206-1331°C (olivine), 1220-1284°C and 0.9-1.3 GPa (clinopyoxene), indicating that early crystallization occurred at or below the Moho. Olivine oxygen isotopes measured by SIMS range from 4.71 to 5.44‰ and average 5.15 ± 0.52‰ and encompass values for clinopyroxene (4.97 ± 0.36‰) and (5.17 ± 0.10‰) measured by laser fluorination. Correlation between oxygen isotopes and degree of partial melting (i.e. Nb/Y) suggests that lower degree melts preferentially consume a lower δ18O source interpreted as metasomatic veins in the lithospheric mantle. Temperature and pressure estimates across the continent-ocean transect indicate a region of lithospheric necking previously identified for Northern Victoria Land. Evidence for disequilibrium observed texturally and compositionally in minerals suggests complex crustal processes, mainly in the ocean-continent transition zone. The results of this study support previous suggestions that late Cenozoic alkaline magmatism in the West Antarctic Rift System is controlled by variations in partial melting of a heterogeneous mantle source and highlights future potential to investigate physical controls on volcanism at magma-poor rift margins.

Committee:

Kurt Panter, Dr. (Advisor); John Farver, Dr. (Committee Member); Deering Chad, Dr. (Committee Member)

Subjects:

Geology; Petrology

Keywords:

alkaline basalt; Northwest Ross Sea; Antarctica; mineral chemistry; oxygen isotopes; metasomatism

Antibus, Joanne VinopalA Petrographic, Geochemical and Isotopic(Sr, O, H and C) Investigation of Alteration Minerals in Volcaniclastic Rocks at Minna Bluff, Antarctica: Petrogenesis and Implications for Paleoenvironmental Conditions
Master of Science (MS), Bowling Green State University, 2012, Geology
The petrography and geochemistry of alteration minerals in volcaniclastic deposits at Minna Bluff; a 45 km-long volcanic peninsula in the southern Ross Sea that was active between 12 and 4 Ma, are used to reconstruct environmental conditions during their formation. The volcaniclastic deposits are intercalated with lavas and domes and include hyaloclastite, breccia, tuff and sediments. The restricted size and extent of the deposits attest to the ephemeral nature of magma water interaction at Minna Bluff. The paragenesis of alteration minerals reveal phillipsite to form first followed by chabazite and/or carbonates. Carbonates include calcite, low to high Mg calcite (MgCO3 >4%), dolomite, magnesite, siderite and rhodochrosite. Alkali ratios (Na+K/Ca) are high for zeolites (phillipsite <1 to 154 and chabazite 8 to 97) relative to host lavas (<1 to 14). Chemical zoning in zeolites is poorly developed but in carbonates transects show significant variations in Fe, Mn and Sr and Mg/Ca ratios. Carbonate δ18O and δ13C values range from -0.50 to 21.53‰ and -1.04 to 8.98‰, respectively. Chalcedony δ18O and δD values range from 0.68 to 10.37‰ and -187.8 to -220.6‰, respectively. The deuterium values are in the range of Antarctic meteoric water. Carbonate 87Sr/86Sr ratios average 0.70327 ± 0.0009 (1σ) and are within the range of volcanic rocks from the Erebus Volcanic Province. The isotopic evidence indicates that meteoric water (ice/snow) was most likely responsible for the alteration of volcaniclastic rocks at Minna Bluff. Based on zeolite stability and the 13C-18O paleothermometer, the alteration occurred at elevated temperatures (5° to ~100°C), probably during or relatively soon after deposition. High δ18O for Mg-rich carbonates and some quartz suggest 18O enrichment by evaporative distillation from steam vents. The calculated δ18O of water (-25 to -16‰) reveal a broad shift from lighter to heavier values between ~11 Ma and ~8.5 Ma. A warming climate during this period has also been predicted based on sedimentary sequences within core recovered from the nearby ANDRILL AND-1B drillcore.

Committee:

Kurt Panter, PhD (Advisor); Thom Wilch, PhD (Committee Member); John Farver, PhD (Committee Member); Jeff Snyder, PhD (Committee Member)

Subjects:

Geology; Paleoclimate Science

Keywords:

hyaloclastites; Minna Bluff, Antarctica; Sr, O, H isotopes; paleoenvironments; volcaniclastic alteration minerals

Redner, Ellen RMagma Mixing and Evolution at Minna Bluff, Antarctica Revealed by Amphibole and Clinopyroxene Analyses
Master of Science (MS), Bowling Green State University, 2016, Geology
Lava flows from Minna Bluff, Antarctica, are studied in order to provide insight into magma system dynamics, specifically magma mixing. More than 500 lava/dome and volcaniclastic samples that range in age from ~12 to 4 Ma were collected along the 45 km volcanic peninsula. Lava compositions range from basanite to phonolite. A significant proportion of lavas of all whole rock compositions contain amphibole. This study is focused on the textural and compositional characteristics of amphibole and clinopyroxene as a means to understand open system processes causing fluctuations of temperature, pressure during crystallization. Lavas with amphibole (± clinopyroxenes) phenocrysts are texturally diverse and range from porphyritic to glomeroporphyritic. Other phenocrysts consist of olivine, plagioclase, alkali feldspars, magnetite and apatite in a groundmass that varies from holocrystalline to hypohyaline. The amphibole is mostly kaersutite and clinopyroxene is diopside. Compositional zoning in amphibole includes normal, reverse and oscillatory types. The coexisting clinopyroxene is weakly zoned. Amphiboles also exhibit weakly to strongly developed reaction rims, which are produced by decompression and/or increase in temperature. Amphibole phenocrysts have higher Fe/Mg ratios than predicted for equilibrium conditions in basanitic magma and lower ratios than predicted for phonolitic magma. The rims of amphibole phenocrysts in intermediate compositions are mostly in equilibrium but cores of the same grain are not. Clinopyroxene phenocrysts show similar relationships. The amphibole and clinopyroxene phenocrysts that are out of equilibrium suggest magma mixing or accidental incorporation of pre-existing crystal `debris’. Geothermobarometric results suggest that amphiboles and clinopyroxenes formed at pressures 4 to 9 kbars (˜ 15-32 km) and 3 to 14 kbars (˜ 11-47 km), respectively. The majority of barometric calculations indicate depths = 22 km, which is at or below the crust-mantle boundary. It is likely that rising melt reached neutral buoyancy at this boundary and pooled, cooled and crystallized to produce more evolved compositions that were, in turn, periodically replenishment by less evolved melts from below. A five stage history is conceived that illustrates the complex nature of magma evolution at Minna Bluff.

Committee:

Kurt Panter, Ph.D. (Advisor); John Farver, Ph.D. (Committee Member); Thomas Wilch, Ph.D. (Committee Member)

Subjects:

Geology

Keywords:

Volcanology; Magma Mixing; Alkaline Magma; Amphibole; Magma Evolution; Minna Hook; Minna Bluff; Antarctica

Konfal, Stephanie AnnAnalysis of Antarctic Crustal Motion Using Remote Sensing and GPS Data: Applications to Ice Mass Change Studies
Doctor of Philosophy, The Ohio State University, 2012, Geological Sciences
Tilted paleoshorelines and GPS data from the Dry Valleys and surrounding region of Victoria Land, Antarctica are analyzed. Paleoshorelines of proglacial lakes were mapped utilizing a multisensor approach, and tilts were derived from elevations along strandlines digitized from high-resolution airborne Light Detection and Ranging (LiDAR) digital elevation models (DEMs). Resulting tilts were combined with shoreline age data to determine long-term patterns of crustal deformation. Modern rates of horizontal crustal motion and crustal tilting were derived from GPS stations within the Transantarctic Mountain Deformation (TAMDEF) network and the Antarctic Network (ANET) component of the Polar Earth Observing Network (POLENET). Patterns of crustal motion observed from both GPS and paleoshoreline records are interpreted to document GIA-induced crustal deformation since the Last Glacial Maximum (LGM). A change in earth deformation pattern with time suggests that the weak earth profile beneath the study region permitted successive responses to multiple phases of ice mass change since the LGM. Shoreline tilt directions suggest ice unloading associated with Talos Dome in the northern Victoria Land and Wilkes Land sectors of East Antarctica. Unloading in this region is not represented in models of GIA for Antarctica, suggesting current GIA models underpredict ice mass loss and resultant rates of rebound for northern Victoria Land and Wilkes Land sectors of East Antarctica. Significantly, such an underprediction of GIA rebound rates indicates that estimates of East Antarctic ice mass balance derived from the Gravity Recovery and Climate Experiment (GRACE) satellite-based studies, which are strongly dependent on GIA model corrections, have underestimated ice mass loss from the East Antarctic ice sheet.

Committee:

Terry Wilson (Advisor); Michael Bevis (Committee Member); Ian Howat (Committee Member); Wendy Panero (Committee Member)

Subjects:

Geological

Keywords:

GPS; paleoshorelines; GIA; Antarctica; crustal deformation

Patel, Angira NIDENTIFICATION AND COMPARISION OF FUNGI FROM DIFFERENT DEPTHS OF ANCIENT GLACIAL ICE
Master of Science (MS), Bowling Green State University, 2006, Biological Sciences
Glacial ice serves as a unique preservation matrix for contemporary and ancient microorganisms. The main objective of this study was to evaluate and test the existence of the fungi encased in ancient glacial ice of Antarctica and Greenland. PCR (polymerase chain reaction) amplification was used to isolate the DNA followed by DNA sequencing to obtain the DNA sequences of the ancient microorganisms. Most of the sequences obtained from ancient microbes were similar to the contemporary fungi. Few fungi cultured were approximately 10,000 years old. Microorganisms isolated from ancient glacial ice have undergone repeated phases of evolutionary changes, such as irradiation, freezing and thawing, and in the process they have been archiving various biogenic materials over the period of time. These microorganisms entrapped in glacial ice provide valuable information about the evolutionary processes, as well as the rich biodiversity during ancient times. Hence, various species of microorganisms may appear to be extinct, but factually they might be dormant, entrapped in ice for millions of years and are capable to reappear amidst suitable conditions. The results of this study can be used in future to relate the biological, biogeochemical and genetic composition to a unique and well characterized geologic history of the fungi entrapped in ancient glacial ice.

Committee:

Scott Rogers (Advisor)

Subjects:

Biology, Molecular

Keywords:

Fungi; Glacial ice; Microorganisms; Greenland; Antarctica

Wovrosh, Alex J.The Role of Regional Sea Surface Temperatures on the Amundsen-Bellingshausen Seas Low as Depicted by Atmospheric Model Intercomparison Project Simulations
Master of Science (MS), Ohio University, 2014, Geography (Arts and Sciences)
Multiple Community Atmospheric Model version 4 (CAM4) simulations, in conjunction with European Centre Hamburg Model version 5 (ECHAM5) and European Centre for Medium-Range Weather Forecasts Interim reanalysis data, are utilized in order to study the Amundsen-Bellingshausen Seas Low (ABSL) from a diagnostic perspective. The underlying goal is to ascertain which forcing mechanisms (e.g., regional sea ice cover, global vs. tropical sea surface temperatures, or radiative forcing), are statistically influential upon the ABSL variations and by extension, regional Antarctic climate. This was accomplished through multiple statistical techniques, such as composite and regression analysis. Results of this work indicate that both CAM4 and ECHAM5 simulations perform relatively well in depicting the seasonal variability of the ABSL (and thus are acceptable for use within this study). It is then shown that different forcing mechanisms affect the ABSL in a non-uniform fashion throughout the year (i.e., dependent upon season). While radiative forcing is necessary to identify many circulation changes with time, this is not true of mean conditions of ABSL or the El Niño-Southern Oscillation teleconnection, where global sea surface temperatures and/ or regional sea ice variations are more influential. Further, while tropical sea surface temperatures are sufficient in producing circulation patterns resembling the Pacific South American Pattern, this tropical forcing alone cannot produce extratropical temperature anomalies. Rather, radiative forcing (and in some cases global sea surface temperatures/ regional sea ice), must also be considered within the model framework to generate more realistic magnitude and spatial extent for these temperature anomalies near the surface.

Committee:

Ryan Fogt, Dr. (Advisor); Dorothy Sack, Dr. (Committee Member); Gaurav Sinha, Dr. (Committee Member)

Subjects:

Atmosphere; Atmospheric Sciences; Climate Change; Meteorology

Keywords:

ABSL; AMIP; West Antarctica; Climate

Elnitsky, Michael A.Tolerance and Physiological Response to Environmental Stress in Antarctic Arthropods
Doctor of Philosophy, Miami University, 2008, Zoology

The Antarctic Peninsula is characterized by harsh and dynamic environmental conditions. Organisms inhabiting this environment may be challenged by extremes of low temperature, limited water availability, dramatic seasonal fluctuations of light availability and ultraviolet radiation, and high salinity. This dissertation describes three projects examining the tolerance and physiological responses to such environmental stress of two Antarctic arthropods, the midge Belgica antarctica and the collembolan Cryptopygus antarcticus.

The first investigation examined the ability of B. antarctica larvae to resist inoculative freezing at subzero temperatures and instead dehydrate as a strategy for winter survival (i.e., cryoprotective dehydration). When cooled to subzero temperatures in the presence of ice, the body fluid melting point was depressed to near equilibrium with the ambient temperature, due to reductions of body water content and the accumulation of several osmolytes, suggesting larvae can undergo cryoprotective dehydration at subzero temperatures. Under more natural conditions, the use of cryoprotective dehydration versus freeze tolerance for winter survival appears to depend upon the moisture content of the surrounding soil.

The purpose of the second study was to assess the tolerance and physiological response to desiccation of C. antarcticus under ecologically-relevant conditions. Slow dehydration at high relative humidities characteristic of the austral summer induced the accumulation of several organic osmolytes and increased the tolerance of water loss. A mild drought acclimation further increased the subsequent desiccation tolerance of C. antarcticus. The springtails were also susceptible to water loss at subzero temperatures and likely rely upon such dehydration as a key component for winter survival.

As B. antarctica microhabitats may be periodically inundated with seawater, the final investigation examined the osmotic response and tolerance of larvae to hyperosmotic seawater exposure. The larvae displayed an impressive tolerance of the osmotic stress, as ~50% survived a 6-d submergence in pure seawater. Hyperosmotic stress induced the accumulation of organic osmolytes and resulted in a significant positive correlation between the rate of oxygen consumption and larval body water content. Finally, a brief seawater acclimation enhanced the subsequent tolerance of freezing and dehydration, but reduced the tolerance of heat shock.

Committee:

Richard Lee (Advisor); Alan Cady (Committee Member); Jon Costanzo (Committee Member); Kathleen Killian (Committee Member); Robert Schaefer (Committee Member)

Subjects:

Biology; Entomology; Zoology

Keywords:

cold-hardiness; Antarctica; insect; Chironomidae; osmoregulation

Poojari, YadagiriEnzyme Immobilization and Biocatalysis of Polysiloxanes
PhD, University of Cincinnati, 2010, Engineering : Materials Science

Lipases have been proven to be versatile and efficient biocatalysts which can be used in a broad variety of esterification, transesterification, and ester hydrolysis reactions. Due to the high chemo-, regio-, and stereo-selectivity and the mild conditions of lipase-catalyzed reactions, the vast potential of these biocatalysts for use in industrial applications has been increasingly recognized. Polysiloxanes (silicones) are well known for their unique physico-chemical properties and can be prepared in the form of fluids, elastomers, gels and resins for a wide variety of applications. However, the enzymatic synthesis of silicone polyesters and copolymers is largely unexplored.

In the present investigations, an immobilized Candida antarctica lipase B (CALB) on macroporous acrylic resin beads (Novozym-435®) has been successfully employed as a catalyst to synthesize silicone polyesters and copolymers under mild reaction conditions. The silicone aliphatic polyesters and the poly(dimethylsiloxane)–poly(ethylene glycol) (PDMS-PEG) copolymers were synthesized in the bulk (without using a solvent), while the silicone aromatic polyesters, the silicone aromatic polyamides and the poly(ε-caprolactone)–poly(dimethylsiloxane)–poly(ε-caprolactone) (PCL-PDMS-PCL) triblock copolymers were synthesized in toluene. The synthesized silicone polyesters and copolymers were characterized by Gel Permeation Chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Wide Angle X-ray Diffraction (WAXD).

This dissertation also describes a methodology for physical immobilization of the enzyme pepsin from Porcine stomach mucosa in silicone elastomers utilizing condensation-cure room temperature vulcanization (RTV) of silanol-terminated poly(dimethylsiloxane) (PDMS). The activity and the stability of free pepsin and pepsin immobilized in silicone elastomers were studied with respect to pH, temperature, cross-link density, organic solvents and storage time using a hemoglobin assay. A notable finding was that free pepsin had zero activity in neutral buffer solution (pH 7) after incubation for 5 hours, while pepsin immobilized in the silicone elastomers was found to retain more than 70% of its maximum normalized activity. These results demonstrate that cross-linked poly(dimethylsiloxane) (PDMS) is a promising support material for the physical entrapment of hydrolytic enzymes such as pepsin.

The Novozym-435 has been widely employed as a biocatalyst for esterification and transesterification of a variety of organic compounds including synthesis of polyesters and polylactones due to its high catalytic-efficiency and high thermal stability in organic media. However, the Novozym-435 was found to have poor mechanical stability and the enzyme was found to leach out from the resin into the organic media. In the present research work, efforts were made to solve the above two problems by chemical immobilization of CALB on surface modified porous silica gel particles. The surface of the porous silica gel particles was silanized using (γ-Aminopropyl)triethoxysilane and then the CALB was chemically crosslinked onto the surface of the silica gel particles using glutaraldehyde. Although the thermal stability of the CALB immobilized silica gel particles was found to be lower compared to that of Novozym-435. The CALB immobilized silica gel particles showed higher enzymatic activity and higher mechanical stability compared to that of Novozym-435.

Committee:

Stephen Clarson, PhD (Committee Chair); Jude Iroh, PhD (Committee Member); Gregory Beaucage, PhD (Committee Member); James Mark, PhD (Committee Member)

Subjects:

Materials Science

Keywords:

Silicone Polyesters;Poly(dimethylsiloxane);Enzyme immobilization;Enzymatic polymer synthesis;Silicone copolymers;Candida antarctica lipase B

Vazquez Becerra, Guadalupe EstebanGEODESY IN ANTARCTICA: A PILOT STUDY BASED ON THE TAMDEF GPS NETWORK, VICTORIA LAND, ANTARCTICA
Doctor of Philosophy, The Ohio State University, 2009, Geodetic Science and Surveying
The objective of the research presented in this dissertation is a combination of practical and theoretical problems to investigate unique aspects of GPS (Global Positioning System) geodesy in Antarctica. This is derived from a complete analysis of a GPS network called TAMDEF (Trans Antarctic Mountains Deformation), located in Victoria Land, Antarctica. In order to permit access to the International Terrestrial Reference Frame (ITRF), the McMurdo (MCM4) IGS (The International GNSS Service for Geodynamics, formerly the International GPS Service) site was adopted as part of the TAMDEF network. The following scientific achievements obtained from the cited analysis will be discussed as follows: (1) The GPS data processing for the TAMDEF network relied on the PAGES (Program for Adjustment of GPS Ephemerides) software that uses the double-differenced iono-free linear combination, which helps removing a big partial of bias (mm level) in the final positioning. (2) To validate the use of different antenna types in TAMDEF, an antenna testing experiment was conducted using the National Geodetic Survey (NGS) antenna calibration data, appropriate for each antenna type. Sub-daily and daily results from the antenna testing are at the sub-millimeter level, based on the fact that 24-hour solutions were used to average any possible bias. (3) A potential contributor that might have an impact on the TAMDEF stations positioning is the pseudorange multipath effect; thus, the root mean squared variations were estimated and analyzed in order to identify the most and least affected sites. MCM4 was found to be the site with highest multipath, and this is not good at all, since MCM4 is the primary ITRF access point for this part of Antarctica. Additionally, results from the pseudorange multipath can be used for further data cleaning to improve positioning results. (4) The Ocean Tide Modeling relied on the use of two models: CATS02.01 (Circum Antarctic Tidal Simulation) and TPXO6.2 (TOPEX/Poseidon) to investigate which model suits the Antarctic conditions best and its effect on the vertical coordinate component at the TAMDEF sites. (5) The scatter for the time-series results of the coordinate components for the TAMDEF sites are smaller when processed with respect to the Antarctic tectonic plate (Case I), in comparison with the other tectonic plates outside Antarctica (Case II-IV). Also, the seasonal effect due to the time-series seen in the TAMDEF sites with longer data span are site dependent; thus, data processing is not the reason for these effects. (6) Furthermore, the results coming from a homogeneous global network with coordinates referred and transformed to the ITRF2000 at epoch 2005.5 reflect the quality of the solution, obtained when processing TAMDEF network data with respect to the Antarctic tectonic plate. (7) An optimal data reduction strategy was developed, based on three different troposphere models and mapping functions, tested and used to estimate the total wet zenith delay (TWZD) which later was transformed to precipitable water vapor (PWV). PWV was estimated from GPS measurements and validated with a numerical weather model, AMPS (Antarctic Mesoscale Prediction System) and radiosonde PWV. Additionally, to validate the TWZD estimates at the MCM4 site before their conversion into the GPS PWV, these estimates were directly compared to TWZD computed by the CDDIS (Crustal Dynamics Data Information System) analysis center. (8) The results from the Least-Squares adjustment with Stochastic Constraints (SCLESS) as performed with PAGES are very comparable (mm-level) to those obtained from the alternative adjustment approaches: MINOLESS (Minimum-Norm Least-Squares adjustment); Partial-MINOLESS (Partial Minimum-Norm Least-Squares adjustment), and BLIMPBE (Best Linear Minimum Partial-Bias Estimation). Based on the applied network adjustment models within the Antarctic tectonic plate (Case I), it can be demonstrated that the GPS data used are clean of bias after proper care has been taken of ionosphere, troposphere, multipath, and some other sources that affect GPS positioning. Overall, it can be concluded that no suspected of bias was present in the obtained results, thus, GPS is indeed capable of capturing the signal which can be used for further geophysical interpretation within Antarctica.

Committee:

DOROTA A. GREJNER-BRZEZINSKA, PhD (Advisor); BURKHARD SCHAFFRIN, PhD (Committee Member); TERRY WILSON, PhD (Committee Member)

Subjects:

Geology; Geophysics

Keywords:

GPS; GEODESY; ANTARCTICA; TAMDEF

Willis, Michael J.Crustal motion in the Antarctic interior from a decade of global positioning system measurements
Doctor of Philosophy, The Ohio State University, 2008, Geological Sciences

A decade of Global Positioning System (GPS) data have been collected at bedrock sites in southern Victoria Land, Antarctica. Measured motions of the crust have been examined to determine if ongoing tectonic deformation occurs within the study area, across the structural boundary between East and West Antarctica. Crustal motions are used to test for activity over the offshore Terror Rift, where young faulting is documented, and to asses locally whether the active Erebus volcano deforms the crust. Bedrock motions caused by large scale ice-mass changes that have occurred in the area since the Last Glacial Maximum are also a major focus of the study.

The horizontal GPS motions record Antarctic plate motion of ~15 mm/yr to the southeast. No deformation is observed over the Transantarctic Mountains Front Zone. Very small amounts of deformation are observed along the Terror Rift, however the recorded direction of motions may be the result of Glacial Isostatic Adjustment (GIA), rather than active tectonics. Recorded motions observed to the south of Ross Island suggest that the Terror Rift continues beneath the Ross Ice Shelf. No volcanic loading signal is observed.

Vertical crustal motions exhibit a down-to-the-east tilt over the study area. A suite of earth models, including more than three hundred different mantle viscosity profiles, three different lithospheric thicknesses and three different ice histories, were used to model uplift due to Glacial Isostatic Adjustment driven by ice mass change. None replicate the observed tilt. Two Relative Sea Level curves for the region also could not be replicated by GIA models examined. Comparison of GPS vertical velocities and our GIA models produce well-constrained earth models for the study area, but suggest that current ice history models for the region must be revised to replicate measured crustal motions.

We compare the output of our GPS-constrained models with published crustal uplift rates used in modern ice mass balance estimates from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. Application of our model, with a factor of two weaker West Antarctic mantle, increases the apparent ice mass loss from West Antarctica by about 50%.

Committee:

Terry Wilson (Advisor)

Keywords:

Antarctica; post glacial rebound; glacial isostatic adjustment; GIA; PGR; GPS; tectonics; geodesy; southern Victoria Land

Baek, Sang-HoDEM generation and ocean tide modeling over Sulzberger Ice Shelf, West Antarctica, using synthetic aperture radar interferometry
Doctor of Philosophy, The Ohio State University, 2006, Geodetic Science and Surveying
Accurate knowledge of the Antarctic ice sheet mass balance plays an important role on the global sea level change. Ocean tides (barotropic and baroclinic) and tidal currents cause basal melting and migration of grounding lines, which are all critical to the accurate determination of ice sheet or ice stream mass balance. Ocean tides in the Antarctic Ocean, especially underneath ice shelves or sea ice, are poorly known primarily due to lack of observations with adequate resolution and knowledge of the bathymetry and ice shelf bottom roughness. InSAR has been used to measure the ice sheet mass balance, ice topography, ice stream velocity, and the location of the grounding lines. To properly use InSAR measurements for ice mass balance and because of their high spatial resolution (tens of meters), knowledge of ocean tides underneath the ice shelves needs to be accurately known and with commensurate resolution. Here two-pass differential InSAR (DInSAR) technique is applied for tidal signal modeling underneath the Sulzberger ice shelf, West Antarctica. The fine resolution (60-m) Digital Elevation Model (DEM) over grounded ice and ice shelf, obtained by combining ERS-1/2 tandem InSAR and ICESat laser altimetry, has been used to correct the topography phase from interferograms, resulting in a more accurate time series of vertical deformation measurements. In this study, it is demonstrated for the first time, that observable tidal constituents can be estimated underneath an ice shelf using an InSAR time series. In particular, it is shown that the time series of observed tidal differences from InSAR agrees well with a number of global/regional ocean tide models such as NAO.99b, TPXO.6.2, GOT00.2, CATS02.01, and FES2004, with the regional model, CATS02.01, having the best agreement. The technique developed here can be applied to other ice shelf regions where tide modeling is poor in accuracy and resolution.

Committee:

C. K. Shum (Advisor)

Keywords:

SAR; Synthetic Aperture Radar; InSAR; Digital Elevation Model; Tide modelling; ICESat; Altimetery; Space geodesy; Antarctica; Ice shelf

Olund, Sydney AFe and Nutrients in Coastal Antarctic Streams: Implications for Marine Primary Production in the Ross Sea
Master of Science, The Ohio State University, 2017, Earth Sciences
The Southern Ocean (SO) has been an area of much biogeochemical interest due to the role of Fe limitation for primary production. Primary production is associated with increased carbon sequestration, making it important to characterize and quantify the fluxes of Fe and other nutrients to the ocean. Water samples were collected in the McMurdo Dry Valleys, Antarctica (MDV) from four subaerial streams flowing into the Ross Sea. They were analyzed for macronutrients (N, P, Si) and Fe to determine the potential impact of terrestrial water input on the biogeochemistry of coastal oceanic waters. Our stream data yield an average filterable composition of N3P1 Si100Fe0.8, which is substantially different from the planktonic composition as demonstrated by empirical measurements, and suggests that these streams are a potential source of Fe and P, relative to N and Si, to coastal phytoplankton communities. The behavior and potential colloidal/nanoparticulate speciation of the Fe in these streams was investigated through analysis of three physiochemical forms of Fe - environmentally active Fe (acid-soluble/no filtration), filterable Fe (filtered through 0.4 µm), and dissolved Fe (filtered through 0.2 µm). It has been suggested that the dissolved fraction is mainly nanoparticulate and represents a more bioavailable form of Fe, as compared with colloids and particles. Overall, the combined average annual flux from two MDV streams is approximately 240 moles fFe yr-1, which is consistent with previously predicted values. The dissolved fraction of Fe (<0.2 µm) was between 18% and 27% percent of the fFe, meaning the fFe pool is mostly colloidal. While the Fe flux from these streams is several orders of magnitude less than aeolian and iceberg sources, terrestrial streams are expected to become a more significant source of Fe to the Ross Sea. As the Antarctic climate warms, ice-free regions similar to the MDV should increase in extent and glacier melt. This study questions how, and in what quantities, Fe is solubilized and transported from the landscape into the SO to better inform predictions of Fe fluxes following continued warming.

Committee:

Berry Lyons (Advisor); Yu-Ping Chin (Committee Member); Michael Durand (Committee Member)

Subjects:

Geochemistry

Keywords:

Iron biogeochemistry; nutrients; Antarctica; primary productivity

Dusselier, Hallie E.Understanding 20th Century Antarctic Pressure Variability and Change in Multiple Climate Model Simulations
Master of Science (MS), Ohio University, 2016, Geography (Arts and Sciences)
The CAM5 non-coupled Community Atmospheric model version 5 (CAM5) is used to study the role that natural and anthropogenic forcings (ozone forcing, radiative forcing, tropical forcing) play in the Antarctic pressure pattern in the last century. Seasonal pressure reconstructions at key Antarctic stations through the 20th century are employed as the best estimates of Antarctic pressure variability since 1905, especially as it is shown here that pressure reanalyses are unreliable in the early 20th century. Three experiments are conducted with the CAM5 model; the first of these experiments allows radiative forcings to vary in time with prescribed, time-varying tropical sea surface temperatures, with the goal being to isolate the role of radiative forcings on the pressure pattern over the continent (when compared with another simulation), and to act as the control, as this is most like the real world. The second experiment that is performed with the model has time varying ozone forcing and climatological sea surface temperatures. The goal of this experiment is to isolate the role of ozone forcing on the Antarctic pressure pattern. The final experiment has fixed radiative forcing at 1990 values, but time-varying prescribed tropical sea surface temperatures. The goal of this experiment is to isolate the role of tropical sea surface temperature variability, or aid in isolating the role of radiative forcing when compared with the first experiment. While each of the simulations of the model results contained interanual variability as expected, the results of the model in each experiment were well within the range of the pressure reconstructions, demonstrating reliability. Additionally, when smoothed, similarities between experiment trends and reconstructions trends were clearly identifiable. Model trends showed that tropical sea surface temperatures have a marked influence on the negative pressure trends in Antarctica, particularly near the Peninsula and West Antarctica and near the Amundsen and Bellingshausen Seas. It is also seen that tropical forcing has the most significant impact during MAM, JJA, and SON during the 20th century. During DJF, a stronger influence from ozone is seen, particularly after 1957. In this season, ozone influenced the negative trends across the continent more uniformly, with more positive trends seen in the southern midlatitudes in DJF after 1957.

Committee:

Ryan Fogt (Advisor); Jana Houser (Committee Member); Dorothy Sack (Committee Member)

Subjects:

Atmosphere; Atmospheric Sciences; Climate Change; Geography; Meteorology

Keywords:

20th century; Antarctica; Climate; Antarctic pressure variability; MSLP; Ozone; Sea surface temperature; CAM5; SAM; ASL

Shtarkman, Yury MMetagenomic And Metatranscriptomic Analyses Of Lake Vostok Accretion Ice
Doctor of Philosophy (Ph.D.), Bowling Green State University, 2015, Biological Sciences
Abstract: Lake Vostok (Antarctica) is the 4th deepest lake on Earth, the 6th largest by volume, and 16th largest by area, being similar in area to Ladoga Lake (Russia) and Lake Ontario (North America). However, it is a subglacial lake, constantly covered by more than 3,800 m of glacial ice, and has been covered for at least 15 million years. As the glacier slowly traverses the lake, water from the lake freezes (i.e., accretes) to the bottom of the glacier, such that on the far side of the lake a 230 m thick layer of accretion ice collects. This essentially samples various parts of the lake surface water as the glacier moves across the lake. As the glacier enters the lake, it passes over a shallow embayment. The embayment accretion ice is characterized by its silty inclusions and relatively high concentrations of several ions. It then passes over a peninsula (or island) and into the main basin. The main basin accretion ice is clear with almost no inclusions and low ion content. Metagenomic/metatranscriptomic analysis has been performed on two accretion ice samples; one from the shallow embayment and the other from part of the main lake basin. Ice from the shallow embayment contains a variety of Bacteria as well as a few Archaea and several types of Eukarya. Most are related to species that are psychrophilic, marine, aquatic, or live in lake/ocean sediments, or a combination of these. However, sequences identified as originating from many different thermophiles were found, suggesting the presence of hydrothermal activity in the lake. In contrast to the embayment ice, the ice from the main basin yielded only about 5-6% of the number of sequences. Here again, molecular signatures of psychrophiles, marine, aquatic, a few sediment-dwelling organisms, and a few thermophiles were found. Because of the extreme conditions, it has been hypothesized that Lake Vostok is sterile, or that very few types of organisms inhabit the lake. Our results indicate that it contains a diverse set of organisms, and the number and taxonomic composition varies with position in the lake.

Committee:

Scott O. Rogers, Dr. (Advisor); Paul F. Morris, Dr. (Committee Member); Vipaporn Phuntumart, Dr. (Committee Member); Robert Michael McKay, Dr. (Committee Member); Rober W. Midden, Dr. (Other)

Subjects:

Bioinformatics; Biology; Ecology; Limnology; Molecular Biology

Keywords:

Lake Vostok; subglacial lake; Antarctica; accretion ice; metagenomic; metatranscriptomic; 454 pyrosequencing; Bacteria; Eukarya; Archaea

Pon, KarenThe Representation of Low Cloud in the Antarctic Mesoscale Prediction System
Master of Science, The Ohio State University, 2015, Atmospheric Sciences
The accuracy of cloud prediction in Antarctica can have a significant impact on aviation operations. Unforecast low cloud can endanger an aircraft attempting to land, and affect a pilot’s ability to distinguish the horizon and surface features while in flight. Over-forecasting of low cloud results in fewer missions completed. A number of cloud forecast products have been developed over the years however forecasters often prefer to use the low level relative humidity (RH) fields to forecast low cloud. This study investigated the use of the Stoelinga-Warner algorithm to generate the current Antarctic Mesoscale Prediction System (AMPS) cloud base height forecast and whether a RH threshold could be used as a proxy for cloud base height. The Stoelinga-Warner algorithm was tested using a case study of a mesoscale low in Prydz Bay near Davis station. The algorithm was insensitive to changes in the phase scheme and light extinction threshold used to predict cloud base. Further investigation revealed inadequate quantities of cloud hydrometeors, indicating a problem with the model’s microphysics scheme. Therefore, AMPS combined with the Stoelinga-Warner algorithm does not accurately predict cloud base height. Cloud base heights derived from radiosonde RH thresholds were compared with synoptic observations for Davis, McMurdo and Halley. Lidar observations were also tested against both synoptic observations and radiosonde-derived cloud base heights at Halley. The optimal RH threshold for predicting cloud base height was ~70% at Davis and McMurdo, and ~90% at Halley. AMPS RH data was used to generate cloud base heights at different thresholds, and these were verified against synoptic observations. Results were mixed due to the comparatively large scatter in the model RH field, with the optimal RH threshold changing according to the verification metric used. However there was broad agreement that Davis and McMurdo required a lower RH threshold than Halley. The thresholds found for Davis and McMurdo are consistent with a study by Inoue et al. (2015) which found optimal RH thresholds between 58% and 66% for Davis, Casey and Mawson stations. The reason for the much higher threshold at Halley is unclear, and further studies are required to determine whether a general RH threshold can be applied across the continent to predict cloud base height.

Committee:

David Bromwich (Advisor); Jay Hobgood (Committee Member); Jialin Lin (Committee Member)

Subjects:

Atmospheric Sciences

Keywords:

cloud; antarctica; numerical weather prediction

Leslie, Deborah LThe Application of Stable Isotopes, δ11B, δ18O, and δD, in Geochemical and Hydrological Investigations
Doctor of Philosophy, The Ohio State University, 2013, Geological Sciences
My dissertation research utilizes stable isotopes as tracers of water and solute sources to study specific geochemical (solute origin) and hydrological (glacier meltwater source across a season comparing water contributions from hyporheic zone and/or glacier melt and residence time of precipitation within a managed water supply) problems within McMurdo Dry Valleys (MCM), Antarctica, and Central Ohio, USA. In Chapter II, δ11B isotopic and dissolved B measurements are used to infer the origin of B within MCM aquatic system. Boron stable isotopic values span the range of +12.3‰ to +51.4‰, varying from glacier meltwater streams to the hypolimnion of a highly evaporated hypersaline lake. These data demonstrate that the major sources of B are chemical weathering of alumniosilicates within the stream channels, and a marine source, either currently introduced by marine-derived aerosols or from ancient seawater. In-lake processes create a more positive δ11B through adsorption or mineral precipitation. The glacier meltwater streams, Lakes Fryxell, Hoare, and upper waters of Lake Joyce display a mixture of these two sources, with Lake Joyce bottom waters primarily of marine origin. Lakes Bonney and Vanda and Blood Falls brine are interpreted as having a marine-like source changed by in-lake processes to result in a more positive δ11B, while Don Juan Pond displays a more terrestrial influence. In Chapter III, δ18O and δD are used to trace water source variation via hyporheic zone or glacier melt within two MCM streams over an entire melt season. The isotopic variation of these streams was more negative at the beginning of the season and more positive later. D-excess measurements were used to infer mixing between hyporheic storage and glacier meltwater. It was supported that Von Guerard Stream has a large, widespread hyporheic zone that changes with time and discharge amounts. The chemistry of Andersen Creek also displayed hyporheic zone influence at certain times of the year. This work adds important new information on the role of hyperheic zone-stream interactions, and supports the short term, more physically based, descriptions of hyporheic dynamics explained in the past decade. Chapter IV describes water flow and travel time within a human managed watershed-reservoir system by measuring the δ18O and δD of the precipitation source to the reservoirs and finally to the distribution system, the tap. Generally, the tap waters experienced little lag time in the managed system, having a residence time of about two months. Tap and reservoir waters preserved the precipitation signal with the reservoir morphology acting as an important control. These water supply reservoirs functioned more like a river system with a faster throughput of water and larger variations in chemical parameters. Other water supply reservoirs have a greater capacity with a larger amount of water supply usage through a more lacustrine environment, which displays more constant solute concentrations and longer flow-through times. This work provides a basic understanding of a regional water supply system in central Ohio, reservoir isotopic dynamics, and Ohio precipitation sources.

Committee:

William Berry Lyons (Advisor); Anne E. Carey (Committee Member); Bryan G. Mark (Committee Member); John Olesik (Committee Member)

Subjects:

Environmental Geology; Environmental Science; Geochemistry; Geology; Hydrologic Sciences

Keywords:

Antarctica; McMurdo Dry Valleys; boron isotopes; saline lakes; hyporheic zone; oxygen-18 and deuterium isotopes; Ohio precipitation source

Nyland, Roseanne E.Evidence for early-phase explosive basaltic volcanism at Mt. Morning from glass-rich sediments in the ANDRILL AND-2A core and possible response to glacial cyclicity
Master of Science (MS), Bowling Green State University, 2011, Geology
Sediments recovered between ~354 and 765 mbsf (~15.9-18.4 Ma) in the ANDRILL AND-2A core contain dispersed accumulations of volcanic glass up to 50% by volume and are used to investigate the petrological evolution and influence of glaciations on volcanism in the McMurdo Sound region of Antarctica. Glass-rich sediments include muddy-to-fine sandstone and stratified diamictite. The glass varies in color, size, vesicularity, crystal content, angularity, and from fresh to moderately altered. Fresh glass with delicate cuspate forms suggests they were introduced into the basin as ash fall with minimal reworking. Altered glass has low total oxides (< 97 wt.%), low Ca/K ratios (< 2), high Alteration Index (> 40), and are typically more evolved than fresh glass. Pristine basaltic glasses (MgO 3-7 wt.%) are ne-normative (5-30 wt.%) and have restricted average SiO2 content (45.2 ± 0.8 wt.%). Overall the glass composition shows an increase in SiO2 content up-section. Fractional crystallization models indicate differentiation controlled by plagioclase, olivine, clinopyroxene and magnetite ± amphibole and apatite. Trace element concentrations are typical for Erebus Volcanic Province (EVP) volcanism. The data extends known composition of Mount Morning (18.7-11.4 Ma), the only known EVP Early-Middle Miocene source, to a mafic end, revealing a previously unknown phase of explosive, strongly alkaline, basaltic activity. The glass-rich sediments are part of larger sequences that record numerous glacial advances and retreats in the region. Sediments with high glass contents correspond to ice minimums and, geochemically, Ba/LREE ratios correlate to intervals of ice expansion (decreasing values) and contraction (increasing values) at multiple depths. Higher Ba/LREE may indicate tapping of more volatile-rich magmas. Within a single glacimarine cycle, glass angularity, vesicularity and composition also vary systematically. A model is supported where ice loading and unloading affects the stress state of the crust around a shallow (< 5 km) magma system. During peak glacial periods, the propagation of magma filled fractures is suppressed and volatiles accumulate in response to the fractionation of anhydrous minerals and/or recharge by volatile-rich magmas. Changing stress states during deglaciation allows the volatile enriched magmas to then rise and vesiculate at shallower depths promoting explosive eruptions.

Committee:

Kurt Panter, PhD (Advisor); John Farver, PhD (Committee Member); Jeffrey Snyder, PhD (Committee Member)

Subjects:

Geology

Keywords:

ANDRILL; Antarctica; Mt. Morning; basaltic volcanism; volcanic glass; geochemistry; glacial-volcanism feedback

Goergens, Chad A.20th Century Antarctic Pressure Variability and Trends Using a Seasonal Spatial Pressure Reconstruction
Master of Science (MS), Ohio University, 2017, Geography (Arts and Sciences)
Across Antarctica, most meteorological observations did not begin until the International Geophysical Year of 1957-58, making it difficult to understand Antarctic climate variability during the early 20th century. To overcome this hurdle, this thesis creates, evaluates, and analyzes several seasonal spatial pressure reconstructions that extend back to 1905 across the Antarctic continent. A kriging interpolation method is used to generate the seasonal spatial pressure reconstruction using 19 Antarctic stations as predictors. Multiple evaluation techniques were used to assess the reliability of the spatial pressure reconstructions when compared to ERA-Interim, which is deemed the most reliable gridded pressure dataset after 1979. From all these evaluation metrics, it is concluded that the most reliable spatial pressure reconstructions are for the summer and winter seasons, but all seasons have enough skill to be useful in interpreting pressure variability throughout the 20th century. Using the newly generated spatial reconstructions, it is clearly seen that the negative pressure trend in the late 20th century across the entire continent in DJF is unique when compared to the 100+ year record. Given this uniqueness and contemporary modeling studies, it is likely that stratospheric ozone depletion plays a leading role in the recent negative Antarctic pressure trends in summer. In contrast, the early 20th century in DJF and the entire 20th century for the other seasons are characterized by interannual variability, with strong decadal-scale variability especially prevalent in winter. This highlights the importance of natural variability in causing the majority of ongoing Antarctic circulation pattern changes.

Committee:

Ryan Fogt (Advisor); Gaurav Sinha (Committee Member); Jana Houser (Committee Member)

Subjects:

Atmosphere; Atmospheric Sciences; Climate Change; Geography; Meteorology

Keywords:

Antarctica; kriging; 20th century; Antarctic pressure variability; Interpolation; Climate

Steinhoff, Daniel FrederickDynamics and Variability of Foehn Winds in the McMurdo Dry Valleys Antarctica
Doctor of Philosophy, The Ohio State University, 2011, Atmospheric Sciences
The McMurdo Dry Valleys (“MDVs”) are the largest ice-free region in Antarctica, featuring perennially ice-covered lakes that are fed by ephemeral melt streams in the summer. The MDVs have been an NSF-funded Long-Term Ecological Research (LTER) site since 1993, and LTER research has shown that the hydrology and biology of the MDVs are extremely sensitive to small climatic fluctuations, especially during summer when temperatures episodically rise above freezing. However, the atmospheric processes that control MDVs summer climate, namely the westerly foehn and easterly sea-breeze regimes, are not well understood. The goals of this study are to (i) produce a coherent physical mechanism for the development and spatial extent of foehn winds in the MDVs, and (ii) determine aspects of large-scale climate variability responsible for intraseasonal and interannual differences in MDVs temperature. Polar WRF simulations are run for a prominent foehn case study at 500 m horizontal grid spacing to study the mesoscale components of foehn events, and 15 summers at 2 km horizontal grid spacing to analyze event and temporal variability. The Polar WRF simulations have been tailored for use in the MDVs through modifications to the input soil conditions, snow cover, land use, and sea ice. An objective foehn identification method is used to identify and categorize events, as well as validate the model against LTER AWS observations. The MDVs foehn mechanism consists of a gap wind through a topographic constriction south of the MDVs, forced by pressure differences on each side of the gap and typically set up by cyclonic flow over the Ross and Amundsen Seas. Significant mountain wave activity over the gap modulates the flow response over the MDVs themselves, and pressure-driven channeling drives foehn flow down-valley. During strongly forced events, mass accumulation east of the MDVs from flow around Ross Island is responsible for easterly intrusions, and not a thermally forced sea breeze as previously thought. A variety of ambient flow directions and associated synoptic-scale patterns can result in MDVs foehn, but adequate forcing is necessary to activate the foehn mechanism. The warmest foehn events are associated with amplified circulation patterns that are not associated with particular interannual modes of variability, but instead related to intraseasonal variability forced by the extratropical response to a stagnant MJO. Implications of the findings upon current MDVs paleoclimate theories on the existence of huge melt lakes at the LGM are also presented.

Committee:

David Bromwich, PhD (Advisor); Jay Hobgood, PhD (Committee Member); Jialin Lin, PhD (Committee Member); Jeffrey Rogers, PhD (Committee Member)

Subjects:

Atmospheric Sciences; Meteorology

Keywords:

McMurdo Dry Valleys; Foehn; Antarctica; Mountain Waves; Gap Flow; Polar WRF

Hulett, Sam RwDetrital Zircon Analysis of Permian Victoria Group Sandstones, Transantarctic Mountains, Antarctica
Master of Science, The Ohio State University, 2012, Geological Sciences
The Beacon Supergroup in the central Transantarctic Mountains, the Gondwana sequence of Antarctica, comprises Devonian (inferred) and Permian-Triassic strata. The latter were deposited in an intracratonic basin which evolved into a foreland basin in mid Permian time. Sedimentary petrology and paleocurrent data indicate that this basin had two major detrital sources, a cratonic source and a volcaniclastic source that characterizes the upper Buckley Formation and younger Triassic beds. In order to investigate the sedimentary provenance further, detrital zircons have been examined from both flanks of the basin. At Clarkson Peak, samples were collected from the lower (quartzose) and upper (volcaniclastic) Buckley Formation. At Mt. Bowers the complete Permian section, from pre-glacial to upper Buckley strata, was collected. Results show varied zircon age provenance, reflecting multiple source regions. In all pre-upper Buckley samples the major zircon provenance is in the 650-480 Ma age range, corresponding to overlapping Ross and Pan African orogenic events, with a subsidiary province of “Grenville age”, ~1000 Ma. These age range variations reflect the influence of multiple sub-provinces. There are also minor contributions from older Proterozoic sources, including a ~1500 Ma source that waned in Fairchild time and is nearly absent in the Buckley Formation. These older Proterozoic zircons were likely sourced from the coast of East Antarctica. A major shift in paleoflow directions between the lower and upper Buckley at both localities is accompanied by a significant input of Permian-age igneous zircons, documenting contemporaneous magmatism and flooding of the basin with detritus from an active magmatic arc. There is also a minor input of ~370 Ma grains which were most likely sourced from Devonian granitoids in West Antarctica.

Committee:

David Elliot (Advisor); Matt Saltzman (Committee Member); Larry Krissek (Committee Member)

Subjects:

Geology

Keywords:

Antarctica; Beacon; Permian; Sandstone Petrology; Detrital zircon

Stafford, Samuel JA Search for Ultra-high Energy Cosmic Neutrinos: Data Analysis of the Antarctic Impulsive Transient Antenna, Third Flight
Doctor of Philosophy, The Ohio State University, 2017, Physics
Ultra-high Energy (UHE) neutrinos represent an increasingly important messenger in astronomy and astrophysics. The Antarctic Impulsive Transient Antenna (ANITA) experiment campaign utilizes a balloon-borne phased antenna array to detect coherent Cherenkov radio-frequency pulses induced by UHE neutrinos interacting with the Antarctic ice. We analyzed the data from the third ANITA flight (ANITA-III) for evidence of Ultra-high energy neutrinos by augmenting interferometric methods used in analyses of previous ANITA flights. Continuous wave (CW) radio content from ground-based Antarctic habitations and orbiting geostationary communications satellites interferes with the detection and analysis of neutrino-induced radio signals; we developed circular polarization analysis methods to facilitate improved rejection of false positives induced by satellite CW. We also developed new methods of calculating signal-to-noise ratio (SNR) of event waveforms, and enhanced event localization by applying a probability distribution function (PDF) based on the measured resolution of our interferometry. We developed a final linear discriminant cut for rejecting thermal and anthropogenic signals by dividing the continent into equal-area bins and optimizing the cut to each individual bin, so as to obtain the strongest possible the upper limit on cosmic neutrino flux.

Committee:

James Beatty, PhD (Advisor); John Beacom, PhD (Committee Member); Amy Connolly, PhD (Committee Member); Richard Kass, PhD (Committee Member)

Subjects:

Astrophysics; Physics

Keywords:

neutrinos; interferometry; radio; antarctica; ANITA; antarctic impulsive transient antenna; ultra high energy neutrinos; astroparticle physics; askaryan;

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