2002-2003 Science Planning Summary

Glaciology

Dr. Julie Palais
Program Manager

IO-194-E

NSF/OPP 01-24014
Station: Not based at a station
Research Site(s): South Shetland Islands

AMS Radiocarbon Chronology of Glacier Fluctuations in South Shetland Islands during Glacial/Interglacial Hemicycle: Implications Antarctica's Role in Global Climate Change
Dr. Brenda L. Hall
The University of Maine
Institute for Quaternar/Climate Studies
Department of Geological Sciences
brendah@maine.edu

Deploying Team Members: Brenda L Hall
Research Objectives: What drives glacial cycles? Most researchers agree that Milankovitch seasonal forcing paces the ice ages, but how these changes are leveraged into abrupt global climate change remains unknown. A current popular view is that the climate of Antarctica and the Southern Ocean leads that of the rest of the world by a few thousand years or more. The character of deglaciation in Antarctica is that of a long gradual warming, rather than an abrupt change, although the paleoclimate record is not well defined. The most persistent challenge to the asynchrony hypothesis is the Taylor Dome ice core. Revision to the chronology has shown that the original interpretation of rapid climate change synchronous with deglaciation in Greenland was probably an artifact of very low accumulation rates.

Millennial-scale fluctuations of high-level, closed-basin, amplifier lakes in the dry valleys of Antarctica can shed some light on this issue: 150 radiocarbon dates of algae from deltas and shorelines record rapid oscillations of these high-elevation lakes that extend through the Holocene. This record has the potential to form an independent data set with which to test the synchrony of abrupt climate changes in Antarctica. However, this approach has several shortcomings, including the fact that the record in the Holocene and earlier is unclear, a lake-level record based on geomorphological features alone is discontinuous, and only levels higher than the present lakes are recorded.

The ideal way to address these problems is to integrate the geomorphological record with a series of cores taken from lake bottoms. Researchers will obtain transects of long cores from Lakes Fryxell, Bonney, Joyce, and Vanda, using an approach designed to extract the greatest possible amount of data. Estimates of hydrologic changes will come from different proxies. Chronology will come from dating of carbonates, as well as luminescence sediment dating. Evaluation of the link between lake level and climate will come from modeling

Combination of the more continuous lake-core sequences with the spatially extensive geomorphological record will result in an integrated data set that extends back at least 30,000 years. This record will be compared with dry valley glacier records and ice cores to address questions of regional climate variability and then with other Southern and Northern Hemisphere records to assess the interhemispheric synchrony or asynchrony of climate change.


Field Season Overview:
This project will work in close collaboration with a compatible GPS-based geophysics project under Dr. Frederick W. Taylor (GO-080-O).

Researchers will accompany Dr. Taylor's party ashore at each of the eight island GPS locations, where they will assess the suitability of glaciologic observations. They may establish a tent camp at locations they consider to be of interest. Other locations will be visited and studied as time permits.

Zodiac support from the R/V Laurence M. Gould will be provided, as well as enough camping equipment to remain ashore for two to three days at each site.