Date of Award

5-2013

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

Brenda L. Hall

Second Committee Member

George H. Denton

Third Committee Member

Daniel F. Belknap

Abstract

Understanding the history of the Antarctic Ice Sheet is crucial to predicting accurately the future stability of the ice sheet and its possible contributions to global sea level. Glacial and glaciolacustrine deposits in Salmon Valley along the coast of McMurdo Sound indicate that a lobe of the Ross Sea Ice Sheet intruded into the valley during the maximum of the last glaciation. The ice blocked the valley mouth and dammed proglacial lakes. Radiocarbon ages of algae collected from the valley floor and along the headlands show that ice at Salmon Valley was at or near its maximum elevations from ~18,000 to ~13,900 yr BP and extended to 320 m above sea level. Deglaciation began after ~13,900 yr BP, although grounded ice continued to block the valley mouth until ~7,600 yr BP.

These results indicate that ice in the Ross Sea remained at or near its maximum at the same time that glaciers elsewhere in the southern hemisphere underwent retreat. One possible explanation for this discrepancy may be rising air temperatures, which caused increased precipitation over Antarctica but rapid ice recession in the southern midlatitudes.

Results from this study do not support the idea that the Ross Sea sector of the Antarctic Ice Sheet served as a source for meltwater pulse 1a (mwpla) at 14,600 yr BP. Deglaciation at Salmon Valley only began after ~13,900 yr BP, well after mwpla is thought to have occurred. Taken together with results from other glacial geologic studies conducted in the region, it appears unlikely that the Ross Sea sector supplied a significant amount of meltwater to the event. If mwpla indeed came from Antarctica, it must have come from a different region of the ice sheet.

Share