Glacier and Climate Variations in the South Shetland Islands (Antarctica) during and since the Last Glacial Maximum
Principal Investigator - Brenda Hall
Student - Ethan Perry
Supported by the Office of Polar Programs, National Science Foundation
One key problem concerns the synchrony or asynchrony of climate changes north and south of the Antarctic Convergence. It is thought that variations in Antarctic climate might lead or be out of phase with similar changes in South America. If so, a transect across the Drake Passage from Tierra del Fuego to the Antarctic Peninsula should reveal a transition from in-phase to out-of- phase climate behavior. Resolving this question of synchrony or asynchrony is critical for understanding the mechanism behind climate fluctuations.
Sandwiched between the Antarctic Peninsula and the Drake Passage, the South Shetland Islands are in an ideal location to test hypotheses of the timing of climate changes north and south of the Antarctic Convergence. Our field work began there in March 2001 and concentrated on ice-free areas of Fildes, Barton, and Byers Peninsulas. We were looking for evidence of former ice extent, as well as for raised beach ridges that were elevated as the land recovered isostatically from glacial depression. We want to address the following questions: How big was the ice during the last glacial maximum (LGM)? Did it extend offshore? When did it begin to retreat? Was retreat interrupted by stillstands or readvances? What is the nature and age of Holocene glacier fluctuations? What is the relative sea-level history of the islands? What role does tectonic uplift play in the formation of raised beaches?
Our work is still preliminary, as we have not yet obtained dates back from the labs. One interesting observation is that there does not seem to be much geomorphological evidence for widespread expansion of ice at the LGM. Moraines dating to this time period are seem to be lacking. Pre-LGM marine features, such as platforms, cliffs, and even beaches are still present. Till is thin and patchy, except in troughs adjacent to outlet glaciers. Possibly the ice was cold-based and did not modify its bed, preserving the older landscape.