Sunlight, clouds, sea ice, albedo, and the radiative budget: the umbrella versus the blanket

• Published in: The Cryosphere
• Main Author: D. K. Perovich
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2018
• Subjects: geo; envir; Arctic; Arctic Ocean; albedo; Sea ice; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-12-2159-2018; https://www.the-cryosphere.net/12/2159/2018/tc-12-2159-2018.pdf; https://doaj.org/article/dad025de8fcd4364b2f3f20c43d3c818

The surface radiation budget of the Arctic Ocean plays a central role in summer ice melt and is governed by clouds and surface albedo. I calculated the net radiation flux for a range of albedos under sunny and cloudy skies and determined the break-even value, where the net radiation is the same for cloudy and sunny skies. Break-even albedos range from 0.30 in September to 0.58 in July. For snow-covered or bare ice, sunny skies always result in less radiative heat input. In contrast, leads always have, and ponds usually have, more radiative input under sunny skies than cloudy skies. Snow-covered ice has a net radiation flux that is negative or near zero under sunny skies, resulting in radiative cooling. Areally averaged albedos for sea ice in July result in a smaller net radiation flux under cloudy skies. For May, June, August, and September, the net radiation is smaller under sunny skies.