NH Snow Cover Extent
Data were provided by the Global Snow Laboratory, Rutgers University. Period of record is 1967-2012 (47 years).
The Northern Hemisphere snow cover extent (SCE) during December 2012 was much above average. The monthly SCE was 46.3 million square km (17.9 million square miles), which was 3.0 million square km (1.2 million square miles) above average and the largest December SCE on record for the hemisphere. The previous record large December SCE occurred in 1985 at 46.0 million square km.
During December, the North American SCE was above average, ranking as the 13th largest December SCE on record. The monthly SCE was 17.2 million square km (6.6 million square miles) — 579,000 square km (224,000 square miles) above the average of 16.6 million square km (6.4 million square miles). During the month, several storms impacted the western and central United States as well as western Canada bringing heavy snowfall. Above-average monthly snow cover was observed in the U.S. and Canadian Rockies and the U.S. Great Plains. Below-average snow cover was observed in the northeastern U.S. and southeastern Canada. For more information on the U.S. December 2012 snow events, please visit the U.S. December Snow/Ice Summary page.
Eurasian SCE was much above average during December. The monthly SCE of 29.1 million square km (11.2 million square miles) was 2.4 million square km (0.9 million square miles) above average and the second largest December SCE on record. The record largest Eurasian December SCE occurred in 2002 with 29.2 million square km (11.3 million square miles) of snow coverage. Above-average snow cover was observed for most of Europe, much of northern China, Mongolia, and Kazakhstan. Below-average snow cover was present in Turkey, the Tibetan Plateau, and the Himalayas.
Sea Ice Extent
According to the National Snow and Ice Data Center (NSIDC), the Northern Hemisphere sea ice extent — which is measured from passive microwave instruments onboard NOAA satellites — averaged for December 2012 was 12.20 million square kilometers (4.71 million square miles), which was 8.70 percent below the 1979-2000 average and the second smallest December Arctic sea ice extent on record. December 2012 was the 18th consecutive December and 139th consecutive month with below-average Arctic sea ice extent. The smallest December snow cover extent occurred in 2010 at 12.02 million square km (4.6 million square miles). December Arctic ice extent is decreasing at an average rate of 3.4 percent per decade.
According to analysis by the NSIDC, the Arctic gained 2.33 million square km (900,000 square miles) of ice during December. Ice growth in the Kara and Barents seas was slower than average, leading to below average ice coverage there during the month. Sea ice in the Labrador Sea was also below average. Ice extent across the North Atlantic has been below-average for several consecutive winter seasons, and is related to higher mortality rates for seals in the region. The bearded and ringed seals were recently added to the list of threatened creatures under the Endangered Species Act. During December above-average ice extent was observed in the Bering Sea.
The December 2012 Southern Hemisphere sea ice extent was 11.28 million square km (4.4 million square miles), 1.5 percent above average, and the 16th smallest (18th largest) December sea ice extent in the 1979-2012 period of record. Antarctic sea ice extent during December has increased at an average rate of 1.9 percent per decade, with substantial interannual variability.
For further information on the Northern and Southern Hemisphere snow and ice conditions, please visit the NSIDC News page.