Geophysics

Thicker Ice Sheets

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Science  13 Oct 2000:
Vol. 290, Issue 5490, pp. 233
DOI: 10.1126/science.290.5490.233c

The amount of water stored as ice in the major ice sheets in the Northern Hemisphere and Antarctica during the Last Glacial Maximum has been uncertain. More ice means higher elevations for the ice sheets, which alters global wind patterns and thus global climate, and lower sea levels. The weight of the great ice sheets also deformed Earth's entire surface; mapping this deformation and the gradual recovery in elevation of areas formerly covered by ice is the main method for reconstructing the ice mass (and also for determining the viscosity of Earth's interior).

The problem is that records of post-glacial rebound in areas formerly covered by the large ice sheets are incomplete, extending back only about half way to the Last Glacial Maximum, about 20,000 years ago. On the basis of these records, several recent models have suggested that the ice sheets were relatively thin, for example, only about 2 kilometers high across Scandinavia. Lambeck et al. show, however, that the short rebound records still can be fit with thick ice sheets in both the Northern Hemisphere and Antarctica (extending to 3 kilometers or more in Scandanavia) if a portion of the ice sheets were to have melted quickly about 19,000 years ago, as some records imply. — BH

Earth Planet Sci. Lett.181, 513 (2000).

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