Elevation and elevation change of Greenland and Antarctica derived from CryoSat-2

Abstract

Abstract. This study focuses on the present-day surface elevation of the Greenland and Antarctic ice sheets. Based on 3 years of CryoSat-2 data acquisition we derived new elevation models (DEMs) as well as elevation change maps and volume change estimates for both ice sheets. Here we present the new DEMs and their corresponding error maps. The accuracy of the derived DEMs for Greenland and Antarctica is similar to those of previous DEMs obtained by satellite-based laser and radar altimeters. Comparisons with ICESat data show that 80% of the CryoSat-2 DEMs have an uncertainty of less than 3 m ± 15 m. The surface elevation change rates between January 2011 and January 2014 are presented for both ice sheets. We compared our results to elevation change rates obtained from ICESat data covering the time period from 2003 to 2009. The comparison reveals that in West Antarctica the volume loss has increased by a factor of 3. It also shows an anomalous thickening in Dronning Maud Land, East Antarctica which represents a known large-scale accumulation event. This anomaly partly compensates for the observed increased volume loss of the Antarctic Peninsula and West Antarctica. For Greenland we find a volume loss increased by a factor of 2.5 compared to the ICESat period with large negative elevation changes concentrated at the west and southeast coasts. The combined volume change of Greenland and Antarctica for the observation period is estimated to be −503 ± 107 km3 yr−1. Greenland contributes nearly 75% to the total volume change with −375 ± 24 km3 yr−1.

Force Balance along Isunnguata Sermia, West Greenland

“…While the datasets are self-consistent over this period, each likely reflects conditions that are unchanging over a different time scale. Observations show that the study area is not undergoing rapid thinning (Pritchard et al, 2009;Helm et al, 2014), suggesting that the surface geometry has been in a relatively steady state over perhaps many decades. However, while the velocity observations in the study area are consistent over multiple years, large changes in ice motion have been observed elsewhere on the ice sheet over time periods much shorter than the decadal scale that is likely represented by the surface geometry (Rignot and Kanagaratnam, 2006;Joughin et al, 2010).…”

“…We use the CryoSat-2 DEM (Helm et al, 2014) to define the ice sheet surface over the study area. It is posted at 1 km resolution.…”

“…This has motivated the collection of new high resolution datasets over the last decade of GrIS surface topography (e.g., Helm et al, 2014;Howat et al, 2014), bed geometry (e.g., Bamber et al, 2013), and surface velocity (e.g., Joughin et al, 2010;Rignot and Mouginot, 2012). While gravity drives the flow of ice, numerous other factors (e.g., basal topography and substrate, ice temperature, and rheology) also influence the basal sliding and deformational motion of the ice sheet in response to gravitational forcing.…”

About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice

“…This is due to the lack of systematic sea-ice thickness measurements in the Southern Hemisphere. There are only few in situ data sets from upwardlooking sonars (only Weddell Sea; e.g., Harms et al, 2001;Behrendt et al, 2013), drillings (e.g., Lange and Eicken, 1991;Ozsoy-Cicek et al, 2013;Wadhams et al, 1987;Perovich et al, 2004), electromagnetic methods (Haas, 1998;Weissling et al, 2011;Haas et al, 2008) and airborne altimetry (e.g., Dierking, 1995;Leuschen et al, 2008). Those data are distributed unevenly in location, coverage and time and do not allow for the estimation of seasonal and interannual sea-ice volume changes.…”

Observation-Based Estimates of Global Glacier Mass Change and Its Contribution to Sea-Level Change

“…These are: repeat altimetry (Csathó et al 2014), DEM differencing (Wang and Kääb 2015), and a combination of these two Helm et al 2014). As shown in Table 1, each of the methods has advantages and disadvantages with regards to temporal and spatial coverage.…”