Arctic sea ice low in January 2012
February 8th, 2012The National Snow and Ice Data Center reports Arctic sea ice extent in January 2012 averaged 13.73 million square kilometers (5.30 million square miles) – the fourth-lowest January ice extent in the 1979 to 2012 satellite data record.
Before 2005 average January ice extent had never been lower than 14 million square kilometers (5.41 million square miles). January ice extent has now fallen below that mark six out of the last seven years.
Large areas of the Barents Sea and the adjoining Kara Sea that are normally locked in ice by now are still open. Sea ice concentration maps posted by Neven at Arctic Sea Ice Blog show how unusual 2012 is:
University of Bremen sea ice concentration maps, cropped
The University of Washington’s Polar Science Center reports Arctic sea ice volume for January 2012 was 16,200 km3 , slightly larger than last year (15,800 km3) but 41% lower than the satellite record era maximum in 1979, 28% below the mean and 1.4 standard deviations from the trend.
Total Arctic sea ice volume from PIOMAS.
Shaded areas indicate one and two standard deviations from the mean.
The melting season starts in about six weeks.
It’s not just sea ice that has been diminishing. In a new study, researchers using satellite measurements calculate that the world’s glaciers and ice caps lost about 148 billion tons, or about 39 cubic miles of ice annually from 2003 to 2010. This total does not count the mass from individual glacier and ice caps on the fringes of the Greenland and Antarctic ice sheets, which could add up to an additional 80 billion tons. The researcher’s data shows total sea level rise from all land-based ice on Earth, including Greenland and Antarctica, was roughly 1.5 millimeters per year from 2003 to 2010, cumulatively about 12 millimeters. The sea rise amount includes the expansion of water due to warming. Thermal expansion of water is the second major contributor to sea level rise, roughly equal to melting ice.
The Greenland and Antarctic ice sheets are losing mass at an accelerating pace. A recent study sponsored by NASA concluded that, if current ice sheet melting rates continue for the next four decades, their cumulative loss could raise sea level by 15 centimeters (5.9 inches) by 2050. When this is added to the predicted sea level contribution of 8 centimeters (3.1 inches) from glacial ice caps and 9 centimeters (3.5 inches) from ocean thermal expansion, total sea level rise by 2050 could reach 32 centimeters (12.6 inches).