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 during April 2012 was much below average and ranked as the fourth smallest April snow cover extent in the 46-year period of record. The monthly snow cover extent was 2.2 million square km (850,000 square miles) below the long-term average of 30.4 million square km (11.7 million square miles). Both the North American and the Eurasian land areas had snow cover extents below average for the month.
During April 2012, the North American snow cover extent was below average, ranking as the eighth smallest April snow cover extent on record. Warmer-than-average temperatures were present across much of the United States and southern Canada during the month, which limited snow cover across those locations. Above-average snow cover was observed in western Canada. The monthly snow cover extent was 12.2 million square km (4.7 million square miles), which is 932,000 square km (360,000 square miles) below average.
Eurasian snow cover extent during April was 15.9 million square km (6.1 million square miles), which was 1.2 million square km (463,000 square miles) below average, ranking as the seventh smallest April snow cover extent on record. During the month, below-average snow cover was observed across central and eastern Russia, northern China, and much of Kazakhstan. Above-average snow cover was present for western Russia and the Tibetan Plateau.
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 April 2012 was 14.73 million square kilometers (5.69 million square miles), 1.8 percent below the 1979-2000 long-term average, and the 17th smallest (18th largest) April sea ice extent in the 1979-2012 period of record. This was the largest April Arctic sea ice extent since 2001. The relatively large April ice extent, in comparison to recent years, was due to a slow rate of ice loss during the first full month of the melt season. April 2012 is the 13th consecutive April and the 131st consecutive month with below-average Arctic ice extent. April Arctic sea ice extent has decreased at an average rate of 2.4 percent per decade.
According to the analysis by the NSIDC, during April, Arctic sea ice was much above average in the Bering Sea, as it was for most of the winter season. Ice extent was below average across Baffin Bay and the Sea of Okhotsk. The areas with above-average ice extent coincided with locations that experienced below-average temperatures in April, and areas with below-average ice extent were consistent with locations experiencing above-average temperatures.
The April 2012 Southern Hemisphere sea ice extent was 7.97 million square km (3.1 million square miles), 9.2 percent above the long-term average — the sixth largest April extent in the 1979-2012 period of record. This marks the largest Antarctic sea ice extent since 2009. Throughout the month, Southern Hemisphere sea ice trended above average. Southern Hemisphere sea ice extent has increased at an average rate of 2.4 percent per decade, with substantial inter-annual variability.
For further information on the Northern and Southern Hemisphere snow and ice conditions, please visit the NSIDC News page.