The Arctic melt season is well underway, and sea ice extent — a key indicator of global warming — declined rapidly during June, setting a record for the largest June sea ice loss in the satellite era. Sea ice extent is currently running just below the level seen at the same time in 2007, the year that set the record for the lowest sea ice minimum in the satellite era.
While the current rate of sea ice decline does not necessarily indicate that another record low will be set this year — weather conditions and other factors could slow the melt before the September sea ice minimum — so far the 2012 melt season has continued the trend of accelerated sea ice loss in the Far North.
Arctic sea ice extent as of July 12, 2012, along with daily ice extent data for the 2007 record melt season. The gray area around the average line shows the two standard deviation range of the data. Click on image for a larger version. Credit: NSIDC.
According to the National Snow and Ice Data Center (NSIDC) in Boulder, Colo., large amounts of sea ice loss were observed during June in the Beaufort, Bering, and Kara Seas as well as Baffin and Hudson Bay. The only area with above average sea ice at the end of June was the eastern Greenland coast, the NSIDC stated.
During June, the Arctic lost a record total of about 1.1 million square miles of ice — an area about as large as the combined land area of Alaska, California, Florida, and Texas. At the end of the month, Arctic sea ice extent was 456,000 square miles below the 1979-to-2000 average. The past three years have seen the lowest June ice extents on record, and this year, sea ice loss is running about three weeks ahead of schedule. The ice extent recorded for June 30 would normally be expected on July 21, based on the 1979-2000 average, the NSIDC said.
Warmer-than-average air temperatures and a lack of snow cover helped speed the melt, according to the NSIDC. In its July 5 analysis, the NSIDC reported that a record low Northern Hemisphere snow cover extent was set for the month of June.
Northern Hemisphere June snow cover anomalies, showing the record low in 2012. Credit: NSIDC.
“This rapid and early retreat of snow cover exposes large, darker underlying surfaces to the sun early in the season,” the NSIDC reported, “fostering higher air temperatures and warmer soils.”
In general, the Arctic has been warming at a rate about twice that of lower latitudes, a trend that is expected to continue due to feedbacks in the Arctic climate system. For example, when sea ice melts, the darker ocean surface is exposed to incoming solar radiation. This warms the water and the air much more than if the brighter sea ice had remained.
Recent research has demonstrated that rapid Arctic climate change is altering the flow of weather systems across the Northern Hemisphere, raising the possibility of far-reaching consequences well south of the Arctic Circle. Increased summer sea ice loss is also helping to open the Arctic to oil and natural gas drilling, as well as increased shipping activities, which could cause further changes to the Arctic environment.