archives@tulane.edu / I present research that improves our understanding of the glacial history of the Antarctic Ice Sheet and advances the method of in situ 14C exposure dating. Firstly, I present research investigating deglaciation in the Weddell Sea Embayment (WSE) sector of the Antarctic Ice Sheet. Large spatial gaps exist in our knowledge of the former configuration of the ice sheet in the WSE because previous studies observe cosmogenic nuclide exposure ages indicative of either significantly thicker ice than present at the Last Glacial Maximum (LGM) or limited (<100 m) thickening. The resulting pattern of past ice thickness is glaciologically unlikely. By measuring the short-lived cosmogenic nuclide in situ 14C in many of the same samples as previous studies, I show that ice at locations thought to have experienced limited thickening was at least 300 to 800 m thicker than present. These new constraints will help future modelling studies in their efforts to simulate the ice sheet and narrow down the contribution to deglacial sea level rise.
Next, I present an investigation into the source of elevated in situ 14C measurements observed from samples that were processed using a mineral separation technique called froth flotation. Multiple organic compounds are required for the use of froth flotation. With modern carbon sources, these organic compounds could introduce carbon contamination to samples. I find that froth flotation introduces modern carbon to samples and contaminant 14C is released with the in situ component. I then outline a procedure that demonstrably removes carbon contamination that can be followed by those isolating quartz for in situ 14C analysis.
Finally, I present an evaluation of the results of numerical ice sheet models using a compilation of exposure ages from the WSE. I use all published post-LGM 10Be and in situ 14C exposure ages from the WSE to assess how well models predict ice thinning histories evidenced by the cosmogenic nuclide measurements. Whilst most models are consistent with minimum geologic constraints for the thickness of the ice sheet, the timing and rate of the majority of post-LGM ice thinning predicted by ice sheet models is often both premature and more rapid than indicated by exposure ages. / 1 / Keir Nichols
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_121676 |
| Date | January 2020 |
| Contributors | Nichols, Keir (author), Goehring, Brent (Thesis advisor), School of Science & Engineering Earth and Environmental Sciences (Degree granting institution), NULL (Degree granting institution) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | electronic, pages: 148 |
| Rights | No embargo, Copyright is in accordance with U.S. Copyright law. |
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