A detailed assessment of snow accumulation in katabatic wind areas on the Ross Ice Shelf, Antarctica

Abstract

An investigation of time dependent snow accumulation and erosion dynamics in a wind-swept environment was undertaken at two automatic weather stations sites on the Ross Ice Shelf between January 1994 and November 1995 using newly developed instrumentation employing a technique which automatically disperses inert, colored (high albedo) glass microspheres onto the snow surface at fixed intervals throughout the year. The microspheres act as a time marker and tracer to allow the accumulation rate and wind erosion processes to be quantified with a high temporal resolution. Snow core and snow pit sampling was conducted twice during the study period to identify microsphere horizons in the annual snow accumulation profile, allowing the snow accumulation/erosion events to be reconstructed. The two sites chosen for this investigation have characteristically different mean wind speeds and therefore allow a comparative examination on the role of wind on ice sheet growth. Mass accumulation rate at the two sites for the 14-day integration periods available ranged from 0.0 to >2.0 kg m−2 d−1. The mean mass accumulation rate during the study period was greater at the site with stronger winds (0.69 kg m−2 d−1) than the site with lower mean wind speeds (0.61 kg m−2 d−1); however, the difference between the two means is not statistically significant. Accumulation rates derived from an ultrasonic snow depth gauge operated at one of the sites are compared to the actual tracer-derived accumulation rates and show the limitations of only having a measure of snow surface height with no instantaneous measurements of the snow density profile. Snow depth gauge derived accumulation rates were found to be greatly overestimated during high-accumulation periods and were greatly underestimated during low-accumulation periods.