Robert P. Ackert Jr., ^1* David J. Barclay, ³ Harold W. Borns Jr., ⁴ Parker E. Calkin, ⁶ Mark D. Kurz, ² James L. Fastook, ⁵ Eric J. Steig ⁷

A lateral moraine band on Mount Waesche, a volcanic nunatak in Marie Byrd Land, provides estimates of past ice sheet surface elevations in West Antarctica. Helium-3 and chlorine-36 surface exposure ages indicate that the proximal part of the moraine, up to 45 meters above the present ice surface, was deposited about 10,000 years ago, substantially later than the maximum ice extent in the Ross Embayment. The upper distal part of the moraine may record multiple earlier ice sheet high stands. A nonequilibrium ice sheet model predicts a delay of several thousand years in maximum ice levels at Mount Waesche relative to the maximum ice extent in the Ross Sea. The glacial geologic evidence, coupled with the ice sheet model, indicates that the contribution of the Ross Sea sector of the West Antarctic Ice Sheet to Holocene sea level rise was only about 3 meters. These results eliminate West Antarctic ice as the principle source of the large meltwater pulse during the early Holocene.

¹ Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program, MS 25, Clark 419,
² Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
³ Department of Geology, State University of New York at Cortland, Cortland, NY 13045, USA.
⁴ Institute for Quaternary Studies,
⁵ Department of Computer Science, University of Maine, Orono, ME 04469, USA.
⁶ Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA.
⁷ Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104-6316, USA.
^*   To whom correspondence should be addressed. E-mail: rackert{at}whoi.edu