Antarctic Science · 1998 · 111 citations · 0 references
Natural SciencesEarth SciencesSoil SciencesClimatologyCryosphere StudiesGlaciologyFrozen Ground ProcessesGround FreezingPeriglacial EnvironmentsPeriglacial ProcessesPermafrostPermafrost ThawFrost PointFrozen Ground Thermal RegimesGround Ice DynamicsGround Temperature DynamicsIce-cored PermafrostNet Heat FluxPermafrost Stability
In the McMurdo Dry Valleys, summer air temperatures would need to rise ~7 °C to thaw the top of subsurface ice, indicating that the ice is either slowly evaporating or being intermittently recharged to maintain long‑term equilibrium. Year‑round measurements show the mean annual frost point of ice‑cemented ground at 25 cm depth is −21.7 °C, slightly warmer than the atmospheric frost point of −27.5 °C, and the ice‑cemented ground is retreating at 0.4–0.6 mm yr⁻¹, with its surface ~12 cm below dry permafrost.
Year-round temperature measurements at 1600 m elevation during 1994 in the Asgard Range Antarctica, indicate that the mean annual frost point of the ice-cemented ground, 25 cm below the surface, is −21.7 ± 0.2°C and the mean annual frost point of the atmosphere is −27.5 ± 1.0°C. The corresponding mean annual temperatures are −24.9°C and −23.3°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 level of the ice-cemented permafrost is about 12 cm below the level of dry permafrost. The summer air temperatures would have to increase about 7°C for thawing temperatures to just reach the top of the subsurface ice. Either subsurface ice at this location is evaporating over time or there are sporadic processes that recharge the ice and maintain equilibrium over long timescales.