The record low in Arctic sea ice recorded in September 2012 when the sea ice extent dropped to just 3.41 million square kilometers was related to high cloud cover over the Arctic region in the early summer, according to new research.
Click to enlarge. Absorbed solar radiation at the top of the atmosphere (red) versus sea ice concentration (black) for the Arctic region between 2000 and 2013. Courtesy: Climate System Laboratory, Seoul, Korea
Researchers have found that the high amounts of cloud in the early summer lead to low concentrations of sea ice in the late summer. This relationship between cloud cover and sea ice is so strong that it can explain up to 80 per cent of the variation in sea ice over as much as 60 per cent of the the sea ice area.
Furthermore, computer climate models fail to capture the role of clouds in mediating the relationship between solar radiation absorbed at the top of the atmosphere in the early summer and Arctic sea ice concentrations in the late summer, according to the research published in the Journal of Geophysical Research Atmospheres.
It has been known for some time that clouds can control absorbed solar radiation, and affect Arctic sea ice process, but the underlying mechanism has been very unclear. This has previously been discussed in research papers by Schweiger et al. 2008, Perovich et al. 2008, Kay et al. 2008; Kay and Gettelman, 2009.
Now scientists led by Yong-Sang Choi of the Department of Environmental Science and Engineering, Ewha Womans University, Seoul, Korea, demonstrate that for the Arctic region the absorbed solar radiation in early-summer months (May-June-July), primarily altered by cloud variations, plays a decisive role in determining Arctic sea ice concentration in late-summer months (August-September-October).
Based on satellite observations of the sea ice extent anomaly over a 13 year period from 2000 to 2012 the researchers have shown that low sea ice concentration in the late-summer months is found whenever the absorbed solar radiation in the early-summer is high. And conversely that sea ice concentrations in the late summer are higher when cloud cover in the early-summer is lower.
Years with anomalously high absorbed solar radiation coincided with anomalously low cloud albedo, low surface albedo, and thus low Arctic sea ice concentration. This occurred in the Junes of 2007, 2011, and 2012 when summer sea ice concentrations had record-breaking low values compared with average values over the previous decades.
This strong solar energy-sea ice connection would serve to better predict Arctic climate change in current climate models that relatively undervalue this as “the models tend to over-emphasize internal sea ice processes in summer,” the researchers state.