Document: MIC-3-58-29

Snow pack coverage and influence on soils of a polar desert.

GOOSEFF, M.N.* ¹, J.E.BARRETT ² and P.T.DORAN ³

University of Colorado, Boulder, CO 80309-0450 USA ¹
Dartmouth College ²
University of Illinois at Chicago ³

Abstract:
The McMurdo Dry Valleys region is the largest of the ice-free areas in Antarctica. As a polar desert, temperatures are low (-20C mean annual air temperature) and precipitation is low (< 15 cm water equivalent annually). Snow events are infrequent and produce less than 1 cm of snow accumulation. During the austral winter, snow is deposited by strong katabatic winds blowing down the valleys from the polar plateau. Due to this aeolian deposition, snow tends to collect in topographic wind shadows (i.e. stream channels, gullies, etc.). During the austral summer of 1999/2000, four existing snow packs were studied in Taylor Valley. Although high ablation rates have been reported on the glaciers of the Dry Valleys (10 to 15 cm yr^-1), there has been little work done to quantify the melt and sublimation of the patchy snow packs on the valley floor. Moisture in the soils is an important component of chemical weathering of the soils, and may be an important source of water to the soil ecosystem. Snow pack area and depth were measured throughout the season. Subnevian and surrounding soil temperature and light intensity were also measured. Subnevian soil samples and snow cores were taken periodically throughout the season to assess the liquid water content changes of the snow and the soil. As the summer progressed, snow density values ranged from 0.23 g cm^-3 to 0.42 g cm^-3. Subnevian soil temperatures started as low as -22C and increased steadily until the soil was directly exposed to the sun, at which time a diurnal temperature swing of as much as 20C was observed. Light intensity sensors underneath the snow pack detected increasing diurnal peaks as the snow ablated from above them. Subnevian gravimetric soil moisture (0.5 % to 11.6%) was always greater than the nearby control soil samples (0.16% to 0.72%). The results of this study show that these seasonal, sparse snow packs may be an important, if only temporary, source of moisture to soils.

Keywords: soil, Antarctica, snow, Dry Valleys

This abstract is being presented at: 3:30 PM in session:
MICROBIAL ECOLOGY