Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

Advisor

Brenda Hall

Second Committee Member

Seth Campbell

Third Committee Member

George Denton

Additional Committee Members

Peter Koons

Robert Ackert

Abstract

Determining the past timing and extent of ice volume changes of the West Antarctic Ice Sheet (WAIS) remains essential for forecasting the rate and magnitude of retreat of the WAIS in the coming decades and centuries. Records of when the WAIS was last smaller than present are sparse and the limited evidence for reduced ice volumes remains a critical gap to address in the paleoclimate community. In this thesis, I examine two lines of evidence of ice volume changes for the WAIS through a relative sea level reconstruction in the Amundsen Sea and from radar observations from field sites across the ice sheet. The relative sea level reconstruction shows that for the Amundsen Sea Sector, ice remained relatively stable for the last 5.5 ka and that the current bedrock uplift rates are an order of magnitude larger than the observed RSL fall during that same period. Conversely, evidence from radar observations collected at sites across the WAIS shows evidence of previous ice surfaces at depths of tens of meters below the modern ice surface and highlight the usefulness of radar studies, that when paired with the collection of ice cores or subglacial bedrock, can provide the timing of readvances. Further, in this thesis I summarize the challenges and successes for the retrieval of subglacial bedrock samples for cosmogenic nuclide analysis from five field campaigns in West Antarctica. This method provides direct evidence for the timing of WAIS retreat during past warm periods but is difficult due to technological and logistical limitations. I focus the findings on drilling efforts and technology and geophysical surveys with ground-penetrating radar and find that 1) a dedicated ground-penetrating radar survey by a practiced geophysicists is necessary given the complex nature of ice near margins, 2) drilling campaigns should start at shallow depths and progress to deeper sites to provide ground truth results for radar surveys and to limit time dedicated to troubleshooting drilling operations, 3) target locations with a clean ice-bedrock interface to prevent drilling complications due to clay overburden, and 4) future drilling campaigns need to balance sites that answer key scientific questions with those that are less challenging to support logistically.

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