Global Snow and Ice - May 2012
Beginning in November 2017, NCEI will use version 3 of the National Snow and Ice Data Center's (NSIDC) monthly sea ice extent index. All historical monthly sea ice extent values will be updated to version 3, but historical reports will not be updated. For additional information on the methodology changes and comparisons to version 2, please visit the National Snow and Ice Data Center.
NH Snow Cover Extent
Data were provided by the Global Snow Laboratory, Rutgers University. Period of record is 1967-2012 (46 years).
The Northern Hemisphere snow cover extent (SCE) during May 2012 was much below average and ranked as the second smallest May SCE in the 46-year satellite period of record. The monthly SCE was 3.47 million square km below the long-term average of 19.4 million square km (7.5 million square miles). This marks the eighth consecutive May with below-average May snow cover for the Northern Hemisphere. Both the Eurasian and North American land areas had below-average snow coverage for the month. For the spring period (March-May), the Northern Hemisphere SCE was 1.9 million square km (735,000 square miles) below average, ranking as the sixth smallest spring snow extent on record. This is the ninth consecutive spring with below-average spring snow cover for the hemisphere.
During May 2012, the North American SCE was nearly 0.8 million square km (310,000 square miles) below average, ranking as the eighth smallest May SCE on record. According to analysis by Rutgers Global Snow Lab, the mountainous West of the U.S. had below-average snow cover during May, as well as most of eastern and central Canada. Above-average snow cover was observed across the Canadian Rockies and southern Alaska. For spring (March-May), the North American SCE was the third smallest on record, 0.9 million square km (0.35 million square miles) below average.
Eurasian SCE during May 2012 was 2.67 million square km (1.0 million square miles) below average, the smallest May snow extent on record for the continent. This is in sharp contrast to February 2012, when the Eurasian SCE was the third largest for the month. A warm spring led to rapid snow melt across much of the continent. According to analysis by Rutgers Global Snow Lab, below-average snow cover was observed across the Alps, most of Russia, the Himalayas, and northwestern China. Above-average snow cover was present for Scandinavia and parts of the Tibetan Plateau. For the spring season (March-May), the Eurasian SCE was nearly 1.0 million square km (386,000 square miles) below average, the 12th smallest spring SCE on record for the continent.
Sea Ice Extent
According to the National Snow and Ice Data Center (NSIDC), the Northern Hemisphere sea ice extent — which is measured onboard NOAA satellites — averaged for May 2012 was 13.13 million square km (5.07 million square miles), 3.46 percent below average. This ranked as the 12th smallest (23rd largest) May sea ice extent on record for the Northern Hemisphere in the 1979-2012 period of record. May 2012 is the 11th consecutive May and the 132nd consecutive month with below-average Arctic sea ice extent. May Arctic sea ice extent has decreased at an average rate of 2.3 percent per decade.
According to the analysis by the NSIDC, sea ice coverage remained above-average across the Bering Sea, similar to the winter and early spring season. The extensive ice in the Bering was countered by below-average ice in the Barents and Kara Seas, resulting in the overall Arctic ice extent being below average. By the end of May, open ocean areas had started to develop along the Arctic coast of Canada. The NSIDC noted that spring Arctic ice extents are not necessarily indicative of ice conditions during summer.
The May 2012 Southern Hemisphere sea ice extent was 10.95 million square km (4.2 million square miles), 2.38 percent above average, and the 15th largest (20th smallest) May extent in the 1979-2012 period of record. Southern Hemisphere sea ice extent was above-average during the first half of May, but trended closer to average in the second half of the month. Antarctic sea ice extent has increased at an average rate of 2.1 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.