SOIL TEMPERATURES AND STABILITY OF ICE-CEMENTED GROUND IN THE MCMURDODRY VALLEYS, ANTARCTICA

Year-round temperature measurements at 1600 m elevation during 1994 in the Asgard Range Antarctica, indicate that the mean annual frost poin t of the ice-cemented ground, 25 cm below the surface, is -21.7 +/- 0. 2 degrees C and the mean annual frost point of the atmosphere is -27.5 +/- 1.0 degrees C. The corresponding mean annual temperatures are -24 .9 degrees C and -23.3 degrees C. These results imply that there is a net flux of water vapour from the ice to the atmosphere resulting in a recession of the ice-cemented ground by about 0.4-0.6 mm yr(1). The l evel of the ice-cemented permafrost is about 12 cm below the level of dry permafrost. The summer air temperatures would have to increase abo ut 7 degrees C for thawing temperatures to just reach the top of the s ubsurface ice. Either subsurface ice at this location is evaporating o ver time or there are sporadic processes that recharge the ice and mai ntain equilibrium over long timescales.