Graduation Year

2021

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Marine Science

Major Professor

Brad E. Rosenheim, Ph.D.

Committee Member

Robert H. Byrne, Ph.D.

Committee Member

Sierra V. Petersen, Ph.D.

Committee Member

Amelia E. Shevenell, Ph.D.

Committee Member

Lauren T. Toth, Ph.D.

Keywords

Isotope Geochemistry, Mass Spectrometry, Paleoglaciology, Radiocarbon

Abstract

Globally averaged Earth surface temperatures indicate a 0.8°C warming since 1880. Though this warming is a result of anthropogenic influence that has exceeded natural forcings, a thorough understanding of Earth's climate system requires a knowledge of changes in global temperatures beyond the instrumental record. To achieve this, we must supplement the temporally limited observational record with proxy records of environmental conditions in the geologic past. Though the foundational questions underlying interrogations of the geologic past are seemingly simple (What happened? When?), the accuracy of their answers depend upon accessibility and availability of geologic materials as well as the capabilities of proxies applied to those materials. Because uncertainties in proxy reconstructions can propagate into projections of future conditions, it is important that we continuously work to expand the utility of geologic archives and the capabilities of proxies and preparatory techniques we apply to them. In this dissertation, I utilize the seldomly accessed sub-ice (subglacial and grounding-line-proximal) sediment record to address questions surrounding the deglacial history of the Ross Sea Embayment, Antarctica. I optimize ramped pyrolysis preparation of acid insoluble organic material in these sediments to assess the timing of past grounding line retreat, and use isotopic (Δ14C, δ¹³C) data to assess the origin, age, and cycling of carbon beneath the West Antarctic Ice Sheet. I demonstrate the utility of sub-ice archives for deglacial paleoglaciological reconstructions by investigating how Holocene-aged carbon is translocated to subglacial sediments. In the interest of addressing questions about past climate, I also present improvements to the mass spectrometry of multiply substituted isotopologues of CO2 (clumped isotopes; Δ47), a promising new isotopic paleothermometer.

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