West Antarctica snow accumulation trend study (1979-2011) from Snow Radar and ice core profiles

Abstract

Ice sheets are under threat from increasing air and ocean temperatures. For Antarctica, observed changes are most apparent near the margins; inland the effects of a warming atmosphere and changing circulation patterns are less clear. Snow accumulation to the ice sheet offsets ice losses near the margin, and characterizing ice sheet accumulation rate is necessary for understanding ice sheet mass balance and predicting future sea level rise. Ice penetrating radar systems enable the measurement of ice sheet properties beneath the surface, such as ice thickness and internal layering. This study concentrates on mapping the depth of internal layers, and linking the layers to a chronology that allows snow accumulation rates over particular time periods to be determined. The focus is on one particular ice penetrating radar system: Snow Radar from the Center for Remote Sensing of Ice Sheet (CReSIS). The Snow Radar is a 2-8 GHz ultra-wideband (UWB), frequency-modulated, continuous-wave (FMCW) radar, having a ~5cm vertical resolution. The chronology of Snow Radar detected layers is validated to be annual layers using nearby ice core data and the results of a regional climate model (RACMO2.1/ANT). The measurement error of a manual layer picking procedure, and proximity of ice core density profiles to the Snow Radar data have been examined. The results show that the average error variance in manual picking is as small as 3.0e-4 m, and that it is reasonable to use ice core density profiles in Snow Radar data processing. Using Snow Radar data, a snow accumulation rate time series has been determined along two flight lines over West Antarctica. The spatiotemporal distribution of snow accumulation has been analyzed and possible explanations for such distribution are discussed. No significant trend is found in snow accumulation during the 33-year study period (1979-2011). The snow accumulation spatial distribution has been related to topography and wind, showing that snow accumulation has a negative correlation with elevation and is generally lower on leeward slopes than on the windward slopes.