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Water-stable isotopes in polar ice cores are a widely used temperature proxy in paleoclimate reconstruction, yet calibration remains challenging in East Antarctica. Here, we reconstruct the magnitude and spatial pattern of Last Glacial Maximum surface cooling in Antarctica using borehole thermometry and firn properties in seven ice cores. West Antarctic sites cooled ~10°C relative to the preindustrial period. East Antarctic sites show a range from ~4° to ~7°C cooling, which is consistent with the results of global climate models when the effects of topographic changes indicated with ice core air-content data are included, but less than those indicated with the use of water-stable isotopes calibrated against modern spatial gradients. An altered Antarctic temperature inversion during the glacial reconciles our estimates with water-isotope observations.

The big ice sheets in Greenland and Antarctica are key elements of the global climate system. By storing large volumes of water as ice or ice-contact lakes and sometimes releasing [...]

Paleoatmospheric records of trace-gas concentrations recovered from ice cores provide important sources of information on many biogeochemical cycles involving carbon, nitrogen, and oxygen. Here, we present a 106,000-year record of atmospheric nitrous oxide (N[sub2]O) along with corresponding isotopic records spanning the last 30,000 years, which together suggest minimal changes in the ratio of marine to terrestrial N[sub2]O production. During the last glacial termination, both marine and oceanic N[sub2]O emissions increased by 40 ± 8%. We speculate that our records do not support those hypotheses that invoke enhanced export production to explain low carbon dioxide values during glacial periods. [ABSTRACT FROM AUTHOR]

A major West Antarctic ice stream discharges by sudden and brief periods of very rapid motion paced by oceanic tidal oscillations of about 1 meter. Acceleration to speeds greater than 1 meter per hour and deceleration back to a stationary state occur in minutes or less. Slip propagates at approximately 88 meters per second, suggestive of a shear wave traveling within the subglacial till. A model of an episodically slipping friction-locked fault reproduces the observed quasi-periodic event timing, demonstrating an ice stream's ability to change speed rapidly and its extreme sensitivity to subglacial conditions and variations in sea level. [ABSTRACT FROM AUTHOR]

A response by the authors to a letter about their articles on the stability of the Antarctic and Greenland Ice Sheets in the March 24, 2006 issue is presented.