Cryosat Delivers Monthly and Inter-Annual Height Change for Some Arctic Ice Caps.

Abstract:

The Cryosat (CS) radar altimeter provides estimates of surface height change, including summer melt and winter snow accumulation, from some Arctic ice caps. The Barnes Ice Cap on Baffin Island, Canada represents the most straightforward situation; essentially snow over ice at all elevations. As illustrated below, the average summer height losses on Barnes were 1.69 ± .36 m (2011), 2.39 ± .36 m (2012), and 1.44 ± .37 m (2013), values which were not balanced by the winter snow accumulation; 0.77 ± .39 m (2011/12), 0.93 ± .33 m (2012/13) and 1.19 ± .43 m (2013/14). However, results from most Arctic ice caps are more complicated: For example, Austfonna in the Eurasian Arctic has a maritime climate with relatively high accumulation and winter conditions that can vary from very cold to rain. Consequently, the distribution of different snow and ice zones varies with position, elevation and time. This leads to a complicated and varying bias between the heights estimated from the radar altimeter waveforms and the physical surface. Nevertheless, under melting conditions the radar returns are dominated by surface backscatter so that observations at the beginning and end of each melt season can provide estimates of net winter accumulation and summer height loss. Results for two Cryosat calibration-validation sites; the Devon Ice Cap in Canada and Austfonna on Svalbard, will be compared with surface and airborne data. Also, estimates of the height and volume change associated with the current surge of basin 3 in Austfonna, which began in earnest in the summer of 2012, will be shown.