Some "old" ice could be quite new



Another reason for skepticism about ice-core proxies for CO2 levels etc. The lower part of an Antarctic drill core may NOT be older than the upper parts -- completely overturning all existing ice-core assumptions. As of now, caution indicates that the lower part of any existing drill core must be taken as uninformative about the past
Science 25 March 2011: Vol. 331 no. 6024 pp. 1592-1595

Widespread Persistent Thickening of the East Antarctic Ice Sheet by Freezing from the Base

Robin E. Bell et al.

ABSTRACT

An International Polar Year aerogeophysical investigation of the high interior of East Antarctica reveals widespread freeze-on that drives substantial mass redistribution at the bottom of the ice sheet. Although the surface accumulation of snow remains the primary mechanism for ice sheet growth, beneath Dome A, 24% of the base by area is frozen-on ice. In some places, up to half of the ice thickness has been added from below. These ice packages result from the conductive cooling of water ponded near the Gamburtsev Subglacial Mountain ridges and the supercooling of water forced up steep valley walls. Persistent freeze-on thickens the ice column, alters basal ice rheology and fabric, and upwarps the overlying ice sheet, including the oldest atmospheric climate archive, and drives flow behavior not captured in present models.

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