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Status of the East Antarctic Ice Sheet
Reference
Mackintosh, A., White, D., Fink, D., Gore, D.B., Pickard, J. and Fanning, P.C. 2007. Exposure ages from mountain dipsticks in Mac. Robertson Land, East Antarctica, indicate little change in ice-sheet thickness since the Last Glacial Maximum. Geology 35: 551-554.

What was done
Noting that "past changes in East Antarctic Ice Sheet (EAIS) volume are poorly known and difficult to measure, yet are critical for predicting the response of the ice sheet to modern climate change," the authors derived altitudinal transects of 10Be and 26Al exposure ages across Mac. Robertson Land's Framnes Mountains, which extend from 10 to 50 km inland of the coast and provide a north-south transect perpendicular to the ice-sheet margin that allows the magnitude and timing of EAIS retreat to be quantified.

What was learned
The new data indicate that the coastal EAIS thinned by no more than 350 meters over the past 13,000 years, and that this reduction occurred over a 5,000-year period that ended with the ice sheet attaining its present profile about 7,000 years ago. "Combined with regional offshore and terrestrial geologic evidence," in the words of Mackintosh et al., these results suggest that "the reduction in EAIS volume since the Last Glacial Maximum was smaller than that indicated by contemporary ice-sheet models and added little meltwater to the global ocean."

What it means
In the concluding paragraph of their paper, the six scientists say that their "finding that the EAIS in Mac. Robertson Land has not undergone major retreat during the past 7,000 years indicates that its adjustment to postglacial sea-level rise ceased earlier than that of the West Antarctic Ice Sheet," which behavior, in their words, "is consistent with satellite-based radar altimetry measurements that indicate that the EAIS interior has grown [our italics] since 1992 in response to an increase [our italics] in snowfall (Davis et al., 2005)." Hence, it would appear that we have little to worry about with respect to the EAIS contributing significantly to global sea level rise for perhaps millennia to come.

Reference
Davis, C.H., Li, Y., McConnell, J.R., Frey, M.M. and Hanna, E. 2005. Snowfall-driven growth in East Antarctic Ice Sheet mitigates recent sea level rise. Science 308: 1898-1901.

Reviewed 26 September 2007