TIMING AND EXTENT OF THE LAST GLACIAL MAXIMUM IN EAST AND WEST ANTARCTICA

The last glaciation in Antarctica culminated 5000-10,000 years after ice sheets in the Northern Hemisphere reached their maximum extent. The continental East Antarctic Ice Sheet (EAIS) and marine West Antarctic Ice Sheet (WAIS) grew and retreated out of phase with one another. Evidently, these ice sheets respond slowly, and at different rates, to changes in surface temperature, snow accumulation and sea level.

In East Antarctica, the Lambert Glacier reached its maximum thickness 17,000-13,000 years ago, and then retreated to its present configuration by 9000 yr B.P.. Exposure ages of erratics from coastal areas overrun by the EAIS in Lutzow-Holm Bay (39° E), the Vestfold Hills (78° E) and Vincennes Bay (111° E) record rapid deglaciation starting 12,000 years ago, and subsequent stabilization of the continental ice-sheet margin by ~10,000 yr B.P.. Exposure dates on erratics from the Bunger Hills (101° E) confirm published suggestions that parts of this oasis remained ice-free during the glacial maximum. As at other East Antarctic coastal sites, ice margins surrounding the Bunger Hills stabilized by ~10,000 yr B.P..

In contrast, exposure dates from the Ford Ranges in Marie Byrd Land show that ice stood more than 700 m above its present height along the West Antarctic coast, 10,000 years ago, and has retreated steadily since. These results, together with other published evidence from the Ross Sea, show that thinning and retreat of the WAIS post-dated both the onset of climatic warming in Antarctica, by ~10,000 years, and all but the final stages of eustatic sea-level rise.

Supported by Australian ASAC awards and NSF grants OPP-9909776 and OPP-9909778.