NH Snow Cover Extent
|April 2021||Snow Cover Extent||1981-2010 Anomaly||Trend
(out of 55 years)
|million km2||million mi2||million km2||million mi2||million km2||million mi2||Year(s)||million km2||million mi2|
Data Source: Global Snow Laboratory, Rutgers University. Period of record: 1967–2021 (55 years)
The April 2021 Northern Hemisphere snow cover extent was 1.38 million square km (530,000 square miles)—equivalent to the size of the country of Peru—below average and was the 11th smallest April extent in the 55-year record. April 2021 also marked the third consecutive April with below-average snow cover extent. The April Northern Hemisphere snow cover extent is decreasing at an average rate of 1.4 percent per decade. During the month, both the North American and Eurasian snow cover extent were below average.
Despite the unusually cool temperatures across much of North America during April 2021, the North America snow cover extent was the tenth smallest April extent on record at 680,000 square km (260,000 square miles) below average. During the month, below-average snow cover extent was observed across much eastern Canada, consistent with the highest warm temperature anomalies across Canada for the month. Other areas with low snow cover extent included parts of southwestern Canada and the northeastern and western contiguous U.S. Overall, averaged as a whole, the contiguous U.S. and Canada's snow cover extent were each below average, ranking as the eighth and 11th smallest for April in the 55-year record, respectively. Alaska's April snow cover extent was near average.
Eurasia's snow cover extent during April 2021 was 690,000 square km (270,000 square miles) below average—the 16th-smallest on record. April 2021 also marked Eurasia's third consecutive April with below-average snow cover extent. Below-average snow cover extent was observed across western Russia and across parts of central and southern Asia. Above-average April snow cover extent was limited to parts of southern Russia, northern Mongolia, and parts of southern China.
Sea Ice Extent
The sea ice extent data for the Arctic and Antarctic are provided by the National Snow and Ice Data Center (NSIDC) and are measured from passive microwave instruments onboard NOAA Satellites. The sea ice extent period of record is from 1979–2021 for a total of 43 years.
|April 2021||Sea Ice Extent||
(out of 43 years)
|million km2||million mi2||Year(s)||million km2||million mi2|
Data Source: National Snow and Ice Data Center (NSIDC). Period of record: 1979–2021 (43 years)
The April 2021 Arctic sea ice extent of 13.84 million square km (5.34 million square miles) was 850,000 square km (330,000 square miles), or about the size of Pakistan, below average. This was the sixth smallest April sea ice extent in the 43-year record. April 2021 marked the 20th consecutive April with below-average sea ice extent. Sea ice extent was below average in the Barents, Bering, and Labrador seas and near average elsewhere. Barents Sea had its fifth smallest April sea ice extent.
The Antarctic sea ice extent for April 2021 was the 16th largest since 1979 at 88,800 square miles, or about the size of Jordan, above average. This was also the largest April sea ice extent since 2016. Sea ice extent was below-average in the northwestern Weddell Sea and northern Ross Sea, where April temperatures were above average.