Summary

There is persuasive marine geological evidence from the relatively well studied Ross Sea embayment, the Bellingshausen Sea, the Amundsen Sea and off the west coast of the Antarctic Peninsula for an LGM ice-sheet grounding line at, or very near to the edge of the continental shelf. A similar situation most likely existed on the eastern side of the peninsula and in the Weddell Sea embayment, though this region has been less well studied to date. LGM thickening of the West Antarctic Ice Sheet has been identified in several locations with the ice surface in the central regions likely to have been several hundred metres higher than today. Likewise ice in the Antarctic Peninsula can be shown to have been up to 500 m thicker at central sites, with the present day ice caps and glaciers coalescing to form the Antarctic Peninsula Ice Sheet at that time.

The smaller number of studies undertaken on the East Antarctic Ice Sheet have found wide variations in the extent of LGM ice advance across the continental shelf. It appears that the grounding line in East Antarctica advanced to the continental shelf break in places, to a mid shelf position in others and for no significant advance to have occurred elsewhere. Furthermore there are several sites, including the Bunger Hills, where deglaciation appears to have begun at around 30 ka BP, well before the LGM.

The timing and rate of deglaciation during the Holocene appears to have varied greatly across the continent. The Antarctic Peninsula Ice Sheet and the Bellingshausen Sea sector of the West Antarctic Ice Sheet may have been amongst the first regions to reach their present configurations while the Ross Sea sector along with many coastal areas in East Antarctica have responded less rapidly to climate and sea-level change since the LGM.

At the end of the 20th century estimates of the reduction in the total volume of the Antarctic Ice Sheets since their maximum during the last glacial cycle ranged from 0.5 to 37 metres of equivalent sea level rise. Recent analysis of the geological evidence has made the upper estimates seem improbable with the consensus of opinion tending towards the upper end of the lower half of this range. Though there is as yet no single agreed value, recent estimates based on geological evidence (Bentley, 1999, 6.1-13.1 m; Denton and Hughes, 2002, 14m) have converged with those based on numerical ice-sheet modelling (Ritz et al., 2001, 5.9 m; Huybrechts, 2002, 19.2m; Philippon et al., 2006, 9.5-17.5m) and those based on modelling of isostatic post-glacial uplift (Nakada et al., 2000, 6.6-16.7 m; Peltier, 2004, 17.3m) to narrow the likely range to 5.9-19.2m sea level equivalent.

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