A drop in mid-summer shortwave radiation induced by changes in the ice-surface condition in the central Arctic

Ice-surface changes during summer and effects on solar heat input in the Arctic were analyzed using incoming shortwave radiation data from drifting buoys deployed in 2002, 2003, and 2004 as part of the North Pole Environmental Observatory project. Observed shortwave radiation was about half of the incoming shortwave radiation at the top of the atmosphere during early summer, suggesting cloudy skies. In each year, events occurred after mid-summer during which time the shortwave radiation decreased 33% to one third of shortwave radiation at the top of the atmosphere. Snow-depth data, aerial photos, and date of melt onset at the buoy site suggest that a decrease in snow/ice albedo induced by snow melting and melt-pond formation modified the amount of shortwave radiation through multiple reflections. A simplified calculation of the ice-albedo feedback revealed that the drop in shortwave radiation after mid-summer was self damping.