Spatial and Temporal Trends in Snow Accumulation From Radio Echo Eounding, Summit, Greenland

Current estimates of snow accumulation over Greenland have large errors (20-25%) because they are derived from a relatively sparse network of point measurements (Ohmura and Reeh, 1991; Bales et al., 2001). To determine whether the Greenland ice sheet mass is increasing or decreasing and how this will affect the global sea level, the Center for Remote Sensing of Ice Sheets (CReSIS) at the University of Kansas has developed several ice penetrating radar systems. Ground based ultra-wideband radar (500-2000 MHz) operated near Summit, Greenland, in July 2005, is used to map near-surface internal layers with 10 cm free- space resolution. This high resolution allows for visual inspection of accumulation layers to a depth of over 200 meters. Radar transects connecting the GRIP and GISP2 ice cores reveal continuous reflection horizons that allow for the transfer of age-depth relationships obtained from the ice cores to the continuous radar reflections. Accurately dated and spatially continuous isochrones are valuable for calibration and verification of ice sheet models. The observed isochrones provide a detailed description of spatial and temporal variations in accumulation rate over the past 500 years and constrain the selection of parameters and climate history used to force numerical models.