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 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 34cm prior to melt to a minimum of 12cm 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 PIOMAS give area-averaged snow depths ranging from 17cm prior to melt to 3cm in August over seasonal ice, and from 34cm to 4cm 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 (>80oN) multiyear ice cover, north of the Greenland coast, is likely due to earlier freeze-up and snow accumulation in these regions with shorter melt seasons.