2003-2004 USAP Field Season

Glaciology

Dr. Julie Palais Program Manager

I-196-M	NSF/OPP 01-24014
Station: McMurdo Station
RPSC POC: Melissa Rider
Research Site(s): Lake Vanda, Lake Bonney, Lake Joyce, Lake Fryxell, Lake Vida, Convoy Range, McMurdo Station, Dry Valleys
Dates in Antarctica: Late December to early February

Millennial-scale fluctuations of Dry Valleys lakes: A test of Implications for regional climate variability and the interhemispheric (a)synchrony of climate change

	Dr. Brenda L. Hall The University of Maine Inst. for Quat./Climate Stud. and Dept of Geol Sci brendah@maine.edu

Sediment coring crew on Lake Fryxell, January 2003. Photo by Brenda Hall.

Deploying Team Members:

Gordon Bromley . Katrina R. Faloon . Brenda L. Hall . Chris Hendy . Erica Hofstee . Thomas Whittaker

Research Objectives: A key unresolved question in antarctic glaciology concerns the stability of the West Antarctic Ice Sheet (WAIS). The WAIS is marine-based, meaning that its substratum is a series of archipelagoes in the northwestern Ross Sea Embayment off the northern Scott Coast. At its relatively fixed position, the WAIS is grounded on the continental shelf with plate boundaries nearby. In contrast, the East Antarctic Ice Sheet sits on a stable lithospheric plate. As deglaciation began after the last glacial maximum (LGM), the WAIS became unmoored. Scientists believe this was likely the first area of the shelf to become free of grounded ice. Learning how and when and in what sequence this occurred is a critical step towards isolating the mechanisms (sea level, climate, ocean temperature, and internal dynamics) that control WAIS dynamics. The northern Scott Coast is of particular interest to researchers looking for mechanisms that may have triggered the key stages of deglaciation. An important first step is to better constrain the age of structures where the inquiry is focused. The Barbados coral record suggests the initial retreat from the Ross Sea Embayment may have begun as early as 17,000 years ago. In contrast, recent glacial geologic mapping and relative sea-level suggests that deglaciation on the southern Scott Coast occurred more recently. Using carbon-14 dating (14C), it appears that deglaciation occurred there during the Holocene (the last 11,000 years) with southward grounding-line migration past Ross Island shortly before 6,500 years ago. This chronology suggests that rising sea level could not have driven grounding-line retreat to the Siple Coast, because deglacial sea-level rise essentially would already have occurred by mid-Holocene. To begin to resolve this conflict, one deficiency in the data from the southern Scott Coast might be corrected. Those data cannot differentiate among the possible triggering mechanisms because they come from 450 kilometers south of the LGM grounding-line position. The goal of this project is to try to overcome this by constructing relative sea-level curves on a transect along the northern Scott Coast. Researchers hope to get the ages for this work from accelerator mass spectrometer 14C dates of seal skins and shells within raised beaches. These curves should reveal when the grounded ice from the northwestern Ross Sea Embayment cut loose.