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Low Clouds Aid Arctic Sea Ice Loss

August 1, 2011 — Click on image to enlarge.

• The Beaufort and East Siberian Sea (BESS) shows a large increase in surface air temperature in the recent decade for months of Sep-Nov.
• Terra covers this important decade when an intensified warming occurred over the Arctic Ocean, and MISR observations provide valuable clues to the problem.
• Causes of the warming remain unclear; but increased absorption of summer solar radiation and autumn low cloud formation have been suggested as a positive ice-temperature-cloud feedback in the Arctic.

 

Major Findings

1. Terra/MISR data reveals a significant increase of low cloud cover in October during 2000-2010, the largest in the daylight Arctic months (March-October), and the result is consistent with CALIPSO lidar observations since 2006.
2. The regions with the largest October low cloud increase collocate with where most sea ice loss occurred in Sep.
3. MISR cloud observations support the theorized positive ice-temperature-cloud feedback, whereby more open water in the Arctic Ocean increases summer absorption of solar radiation, and subsequent evaporation, which leads to more low clouds in autumn. Trapping longwave radiation, these clouds effectively lengthen the melt season and reduce perennial ice pack formation, making sea ice more vulnerable to the next melt season.