Master's Thesis Defense in Earth, Environmental and Atmospheric Sciences: Matthew Witscheber 4/8

03/24/2025
By Matthew Witscheber

The Kennedy College of Sciences, Department of Earth, Environmental and Atmospheric Sciences, invites you to attend a Master's Thesis Defense by Matthew Witscheber on "Sediment and Cation Composition in Buried Glacial Ice of the McMurdo Dry Valleys, Antarctica: Implications for Hydrological Interactions with the Surface Environment."

Date: Tuesday, April 8, 2025.
Time: 1 to 4 p.m.
Location: Olney Hall 212

Advisor: Kate Swanger, Ph.D., Earth, Environmental and Atmospheric Sciences, UMass Lowell

Committee Members
Richard Gaschnig, Ph.D., Environmental and Atmospheric Sciences, UMass Lowell
Jennifer Lamp, Ph.D., Earth and Environmental Sciences, Columbia University

Abstract:

The McMurdo Dry Valleys (MDV), home to the southernmost freshwater ecosystem in the world, displays complex hydrological interactions between local glaciers, snowbanks, meltwater streams and perennially frozen lakes. Significant amounts of freshwater are also stored in the MDV as buried glacial ice deposits, however the extent to which these deposits engage with the surface hydrology remains unknown. Buried glacial ice can also contain high sediment yields, however the mechanisms by which these sediments become incorporated are poorly understood. X-ray Fluorescence (XRF) and Inductively Coupled Optical Emission Spectroscopy (ICP-OES) analyses were done to geochemically compare englacial and surficial sediments, constrain bedrock sources for sediments and compare cation proportions (Ca2+, Mg2+, Na+, K+) between active layer sediments and buried glacial ice. Surface sediment and ice core samples were selected from six MDV sites: three sites in central Taylor Valley, one site in Pearse Valley, and two sites in the Quartermain Mountains, chosen to encompass both warmer, wetter lowland and colder drier upland regions. Sediment-rich ice core layers contained higher major cation concentrations than clean ice layers across all sites, suggesting active meltwater interactions during sediment incorporation. Englacial and surficial sediments are predominantly sourced by local Ferrar Dolerite and Granite Harbour Intrusive outcrops, however widespread, but minor, McMurdo Volcanic Group (MVG) influences suggest that regional winds can transport sediment both westward and eastward in Taylor Valley. Englacial and surficial sediments also appear related, indicating that englacial sediments are likely incorporated at or near the site of deposition and dominantly source from local surface sediments. Relative concentrations of major cations differ significantly between buried ice samples and the soluble salts extracted from surface sediments, suggesting minimal hydrological interactions between the active layer and underlying buried ice.