Antarctic ice sheet volume at 18,000 years B.P. and Holocene sea level changes at the West Antarctic margin

The Antarctic ice sheet has been reconstructed at 18,000 yr B.P. by Hughes et al. (in press) by using an ice flow model. The volume of the portion of this reconstruction that contributed to a rise of post-glacial eustatic sea level has been calculated and found to be (9.8 plus or minus 1.5) x 10 super(6) km super(3) . This volume is equivalent to 25 plus or minus 4 m of eustatic sea level rise, defined as the volume of water added to the ocean, divided by ocean area. The total volume of the reconstructed Antarctic ice sheet was (37 plus or minus 6) x 10 super(6) km super(3) . If the results of Hughes et al. are correct, Antarctica was the second largest contributor to post-glacial eustatic sea level rise after the Laurentide ice sheet. The Farrell and Clark (1976) model for computation of relative sea level changes, caused by changes in ice and water loading on a viscoelastic Earth, has been applied to the ice sheet reconstruction, and the results have been combined with the changes in relative sea level caused by Northern Hemisphere deglaciation, as previously calculated by Clark et al. (1978). Three families of curves have been compiled, showing calculated relative sea level change at different times near the margin of the possibly unstable West Antarctic ice sheet in the Ross Sea, Pine Island Bay, and the Weddell Sea. The curves suggest that the West Antarctic ice sheet remained grounded to the edge of the continental shelf until similar to 13,000 yr B.P., when the rate of sea level rise caused by northern ice disintegration became sufficient to dominate emergence near the margin, predicted otherwise to have been caused by shrinkage of the Antarctic ice mass. The curves suggest that falling relative sea levels played a significant role in slowing, and perhaps reversing, retreat when grounding lines approached their present positions in the Ross and Weddell seas. A predicted fall of relative sea level beneath the central Ross Ice Shelf of as much as 23 m during the past 2000 yr is compatible with recent field evidence that the ice shelf is thickening in the southeast quadrant.