Increasing October low-cloud cover in the Arctic as observed by MISR during 2000-2009

Arctic sea ice loss increases the area of open water and evaporation in the summer, causing more cloudiness in the fall as temperature decreases. The rate of sea ice loss has been substantial in recent years such that a significant increase in low-cloud cover is observed by MISR (Multiangle Imaging SpectroRadiometer) since 2000. Studying vertical distributions of MISR cloud fraction, we find that the low-cloud (< 2 km) cover over the sector near East Siberian Sea has changed from 32% to 55% during 2000-2009 (or ~2.4 %/yr). In the meantime, the high-cloud in the same region decreases at a rate of 1.1 %/yr, yielding an increase of 1.3 %/yr in total cloudiness. The increasing low-cloud cover in October near East Siberian Sea is consistent with the expected consequence from more open water and evaporation associated with the rapid sea ice loss. As Arctic sea ice extent continues to shrink, the expanding open water area will enhance regional air-sea interactions. It is anticipated that Arctic sea ice would become more vulnerable to atmospheric variability. Thus, cloud feedback would play an increasingly important role in polar climate change.