A look at the Antarctic sea ice cover from combined measurements of ICESat-2 and CryoSat-2

Abstract:

With the launch of ICESat-2 in late 2018, polar regions are now sampled at unprecedented temporal and spatial resolutions. Using near-coincident measurements from the ICESat-2 lidar and the CryoSat-2 radar, we examine the variability of several components of the Antarctic sea ice over between April and November of 2019. Observed lidar and radar freeboards are characterized by a high regional variability. Estimates of snow depth (from the freeboard differences) and sea ice thickness indicate that the thickest ice is found in the Western Weddell and the Bellingshausen-Amundsen seas with mean values greater than 2m throughout the season, and thinnest ice near polynyas (Ross Sea and Ronne) where ice is produced and exported seaward. A remarkable mechanical ice convergence event along the coastal Amundsen Sea in 2019 was captured by the satellite observations with a correlated increase in local freeboards and thickness. Despite the consistency in spatial patterns, observations are characterized by a rather weak seasonality, likely due to competing factors affecting the variability of the freeboards (snowfall, snow redistribution, snow-ice formation, ice deformation, basal growth/melt). Further analysis of the results suggests biases in CryoSat-2 freeboards resulting in rather high thickness values in regions of thin and seasonal ice. Given the lack of seasonally and regionally comprehensive data sets, assessment of these large-scale satellite retrievals remain challenging. The recent adjustment of the CryoSat-2 orbit to synchronize with ICESat-2 measurements, will aid in the improved understanding of snow depth and ice thickness retrievals from both altimetry data sets.