The project, carried out in collaboration with Dr. Harold Borns of the University of Maine, will document former ice sheet elevations and access the stability of the West Antarctic ice sheet (WAIS) at the Ohio Range near the head of Mercer Ice Stream (formerly Ice Stream A). The field location is situated in the “Bottleneck”, a unique, relatively narrow passage in the Transantarctic Mountains connecting the West and East Antarctic ice sheets (Figs 1-3). The location lies near the ice divide and is well situated to determine past interior ice elevation.

The research involves geologic mapping of glacial deposits and erosion features combined with cosmogenic surface exposure dating (³He, ²¹Ne, ¹⁰Be, and ²⁶Al) on the Ohio Range nunataks to determine the chronology of past ice sheet levels and local glacier fluctuations. Fresh glacial erratics, up to 60 m above the present ice level, were described by John Mercer in 1963. Exposure ages of these erractics will be used to constrain the timing of the last ice sheet high stand and subsequent draw down of the WAIS in this sector. Exposure ages of debris bands on the ice sheet surface will constrain the duration of continuous ice cover near the present elevation. A complimentary local proxy climate record will also be obtained from a chronology of the local glacier moraines. These glaciers are sensitive to changes in accumulation and dominant wind direction. When compared to the record of the adjacent ice sheet fluctuations, the timing of alpine glacier advance will yield information on climate changes at this location and can be used to test climate reconstructions based on Antarctic ice core records.

Data obtained from our research will contribute to the development of time-dependent, non-equilibrium glacial models of the WAIS, at and since the last glacial maximum 21,000 years ago, which is a major objective of the West Antarctic Ice Sheet Initiative. Age control on ice sheet elevation from this key location, near the head of the Mercer Ice Stream, will complement existing chronologic coverage extending from the ice age terminus in the Ross Sea, through McMurdo Sound and the southern Transantarctic Mountains, to the onset area near the ice divide. Data along the entire length of this ice stream is critical to testing and calibrating the dynamic ice sheet models necessary to predict the future behavior of the ice sheet in response to climate changes. Our research will therefore significantly improve understanding of ice sheet behavior . In addition, the glacial geologic record in the Bottleneck will reflect the history of the interaction of WAIS and EAIS, which could be used to test hypotheses of Pleistocene collapse of the WAIS.

The future behavior of the WAIS is of significant interest to society because of it’s linkage to sea level. Melting of Antarctic ice sheets would raise sea levels, negatively impacting the large portion of the human population living near the world’s coasts. Because the WAIS is largely grounded below sea level, it is subject to gravitational collapse. This collapse may be on-going or could be triggered by global warming. Our research is designed to provide necessary data on the past history of the WAIS to the ice sheet modeling community in order to accurately predict the future behavior of the ice sheet.