Albedo feedback enhanced by smoother Arctic sea ice

The ICESat operational period 2003–2008 coincided with a dramatic decline in Arctic sea ice—linked to prolonged melt season duration and enhanced melt pond coverage. Although melt ponds evolve in stages, sea ice with smoother surface topography typically allows the pond water to spread over a wider area, reducing the ice‐albedo and accelerating further melt. Here we develop this theory into a quantitative relationship between premelt sea ice surface roughness and summer melt pond coverage. Our method, applied to ICESat observations of the end‐of‐winter sea ice roughness, can account for 85% of the variance in advanced very high resolution radiometer (AVHRR) observations of the summer ice‐albedo. An Arctic‐wide reduction in sea ice roughness from 2003 to 2008 explains a drop in ice‐albedo that resulted in a 16% increase in solar heat input to the sea ice cover, which represents ten times the heat input contributed by earlier melt onset timing over the same period.