The Impact Of Glacial Proximity On The Elemental Composition Of Leachate Derived From Sediment Weathering, Karoline Ford

Theses/Capstones/Creative Projects

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This study assesses chemical weathering trends as they relate to glacial retreat. The chemical environment of surfaces exposed to the atmosphere differs significantly from beneath a glacier. As a glacier melts, changes to the biogeochemical processes generate environmental gradients. This study analyzed chemical weathering signals at different distances from a glacial front by comparing the elemental composition of leachate derived from sediments in southeastern Greenland. Samples from proglacial, nonglacial, and moraine locations were weathered in a laboratory setting, and ion chromatography was used to determine the elemental composition of the products. Divergent trends in leachate composition were observed as distance …

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Geomorphic And Paleoclimatic Implications Of Glacial Extent Records In The Sierra Nevada Del Cocuy, Colombia During Termination 1, Jordan Nickerson Herbert

Dartmouth College Master’s Theses

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Reconstructions of past glacial extents using geomorphic mapping and cosmogenic dating provide an opportunity to infer past climates. A record of the past extents of tropical mountain glaciers is particularly useful because there are few other means to reconstruct past temperatures in high-altitude, low-latitude locations. The tropics play an outsized role in mediating global climate, yet there is a lack of understanding of how the tropics may have influenced past climate changes such as the most recent deglaciation (Termination 1, ~18–11.7 ka). Improving reconstructions of tropical mountain glaciers will aid in understanding the role of the tropics in the global …

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Glaciochemical Investigations In Three Southern Hemisphere Mountain Sites, Mariusz Potocki

Electronic Theses and Dissertations

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The research presented in this dissertation focuses on glaciochemical records of trace elements, major ions, and stable water isotopes from three mountain regions: the Antarctic Peninsula, the Central Chilean Andes, and South Georgia Island.

The first section reports a significant increase in U concentration over 27 years on Detroit Plateau, Antarctic Peninsula. U concentrations in the ice core increase by as much as 102 between the 1980s and 2000s, accompanied by increased variability in recent years. The U concentration increase coincides with expanded open pit mining in the Southern Hemisphere, most notably Australia. Since other land-source dust elements do not …

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Variations In The Southern Hemisphere Westerlies Over The Last 23,000 Years From Lake Records In The Falkland Islands, Meghan M. Spoth

Electronic Theses and Dissertations

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The Southern Hemisphere Westerlies (SHW) are an important driver of climate in the mid-latitudes of the Southern Hemisphere. Abrupt latitudinal migration of this coupled atmospheric-oceanic system is thought to be linked to the onset of the Termination at the end of the last ice age and to subsequent climatic variation through the late-glacial period and Holocene. However, the timing and spatial extent of these shifts, as well as variations in wind intensity, are poorly constrained, hindering our understanding of abrupt climate change in the Southern Hemisphere. In addition, future changes in the position and intensity of the SHW are a …

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Mechanisms Of Ice Core Stable Isotope Variability In The Upper Kaskawulsh-Donjek Region, St. Elias Mountains, Yukon, Canada, Erin A. Mcconnell

Electronic Theses and Dissertations

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I use instrumental and ice core records to examine drivers of observed isotope variability in the Upper Kaskawulsh-Donjek (UKD) region of the St. Elias Mountains, Yukon, Canada over the time frame of instrument-proxy overlap (mid-1900s to present). One of the drivers of post-depositional isotope signal alteration is the vertical percolation of meltwater from the glacier surface through shallow layers of snow, which causes a reduction in the amplitude of the isotope signal recorded in ice cores. I examine isotope signal preservation in two sites in the St. Elias Mountains: Eclipse Icefield and Icefield Divide. These sites are relatively close (~30 …

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Arctic And North Atlantic Paleo-Environmental Reconstructions From Lake Sediments, Gregory A. De Wet

Doctoral Dissertations

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ABSTRACT

ARCTIC AND NORTH ATLANTIC PALEO-ENVIRONMENTAL RECONSTRUCTIONS FROM LAKE SEDIMENTS MAY 2017 GREGORY A. DE WET, B.Sc., BATES COLLEGE M.Sc., UNIVERSITY OF MASSSCHUSETTS, AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS, AMHERST Directed by: Drs. Raymond S. Bradley and Isla S. Castañeda There are few fields in the discipline of Earth Science that hold more relevancy in 2017 than studies of earth’s climate. Called the “perfect problem” considering its complexity and magnitude, climate change will continue to be one of the greatest challenges humanity will face in the 21^st century. And while numerical models provide valuable information on conditions in the future, …

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Late Holocene Climate And Environmental Reconstruction Derived From The Asian Ice Core Array (Aica), Bjorn Grigholm

Electronic Theses and Dissertations

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Recent climate change has impacted natural and human systems across the Earth, emphasizing the need for greater understanding of both the existing and changing natural and anthropogenic forcing mechanisms and subsequent responses of the Earth’s climate system. High-resolution, multi-parameter ice core records retrieved and analyzed from two Asian Ice Core Array (AICA) sites, Geladaindong (central Tibetan Plateau) and Inilchek (central Tien Shan) were utilized to reconstruct atmospheric chemical concentrations and composition over the past ~100-500 years, improving the understanding of late Holocene climate and environmental variability in Asia. Both ice cores were analyzed for major and trace elements, major soluble …

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Evidence Of Late Quaternary Fires From Charcoal And Siliceous Aggregates In Lake Sediments In The Eastern U.S.A., Joanne P. Ballard

Doctoral Dissertations

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The late-glacial transition to the Holocene, 15,000–11,600 cal yr BP, is an enigmatic period of dynamic global changes and a major extinction event in North America. Fire is an agent of disturbance that transforms the environment physically and chemically, and affects plant community composition. To improve understanding of the linkages between fire, vegetation, and climate over the late glacial and Holocene in the eastern U.S., I analyzed lake-sediment cores for charcoal and indicators of wood ash, and compared results to existing pollen records. A new microscopic charcoal record from Anderson Pond, Tennessee revealed high fire activity from 23,000–15,000 cal yr …

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Timing And Extent Of The Little Ice Age Glacial Advances In The Eastern Tian Shan, China, Yanan Li

Doctoral Dissertations

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Located in Central Asia, one of the most continental regions on Earth, the Tian Shan’s glaciers contribute critical fresh water to populated areas in the lowland. These glaciers are sensitive to climate change, and knowledge of contemporary glaciers and their changes in the past is of critical importance for sustainable development in this region. Constraining glacial fluctuations in recent centuries will fill a gap in numerical constraints on glacial history and paleoclimate information, and provide important evidence on the spatio-temporal changes of the climate systems in the Tian Shan. This doctoral dissertation investigates the timing and extent of Little Ice …

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Ice-Movement History And Kimberlite Indicator Mineral Dispersal Study, Pelly Bay, Lower Boothia Peninsula, And Wager Plateau Areas, Nunavut, Canada, Carl Ozyer

Electronic Thesis and Dissertation Repository

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This study reconstructs the ice flow history of the eastern portion of the Keewatin sector of the Laurentide Ice Sheet by integrating field work, remote imagery, and work by others. The study reveals at least seven ice flow phases during the Wisconsinan, including ice streams. A model was developed using inverse distance weighed (IDW) interpolation with GIS to identify and isolate potential kimberlite bedrock sources in kimberlite indicator mineral-rich areas in the Pelly Bay area, Nunavut. Kimberlite indicator mineral (KIM) data were normalized by “peer size” to better understand how KIM grains from three kimberlite sources are distributed within three …

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Comparison Of Ice Core Dissolved Organic Matter From A Greenland Ice Core By Nanospray Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, Joshua Jeremiah Shiloh Marsh

Chemistry & Biochemistry Theses & Dissertations

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Recent studies of ice cores have embarked on the task of determining the classes of dissolved organic matter (DOM) present in melt-water from the cores collected in numerous locations in the northern and southern hemispheres. This DOM originally derives from wet precipitation and is thought to reflect atmospheric organic matter derived from anthropogenic and non-anthropogenic sources. Because the amount of DOM is so low, previous studies have necessarily used large sample volumes (greater than 500 mL) to concentrate sufficient ice core DOM necessary for mass spectral analysis. Solid phase extraction (SPE) with C₁₈ resins was followed by evaporative concentration …

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Characterization Of Firn Microstructure Using Scanning Electron Microscopy: Implications For Physical Properties Measurements And Climate Reconstructions, Nicole Spaulding

Electronic Theses and Dissertations

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Samples from 12 East Antarctic firn and ice cores were analyzed using scanning electron micrcoscopy (SEM) in order to first develop a technique for the accurate characterization of physical properties and then to investigate the relationship between the physical microstructure and chemical properties. Both physical properties, such as grain size and porosity, and chemical properties, such as major ion and trace element concentration, provide information about atmospheric temperature changes, impurity content, accumulation rate and deformation history; therefore the characterization of both types of properties is necessary. Further, knowledge of the relationship between the physical and chemical properties may increase our …

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