Decay of the Snow Cover Over Arctic Sea Ice From ICESat-2 Acquisitions During Summer Melt in 2019

From the onset of melt in early June, corresponding declines in Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) freeboard and surface albedo can be seen over the entire Arctic sea ice cover. In the 2019 summer, area-averaged freeboard decreased from 34 cm prior to melt to a minimum of 12 cm in August while the area-averaged albedo decreased from ~0.7 to 0.38 for the same period. Calculations using ICESat-2 freeboards and modeled ice thickness from Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) give area-averaged snow depths ranging from 17 cm prior to melt to 3 cm in August over seasonal ice and from 34 to 4 cm over multiyear ice. Mean rates of snow ablation (including evaporation) in mid-June were as high as 2 cm/day, comparable to field records from other years. Increases in freeboard after mid-August in the high latitude (>80°N) multiyear ice cover, north of the Greenland coast, are likely due to earlier freeze-up and snow accumulation in these regions with shorter melt seasons.