NH Snow Cover Extent
|May 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 Northern Hemisphere snow cover extent for May 2021 was the third smallest in the 55-year record at 16.21 million square km (6.26 million square mi). Only Mays of 2010 and 2012 had a smaller snow cover extent. Nine of the Northern Hemisphere's 10 smallest May snow cover extents have occurred since 2010. May 1968 is among the 10 smallest May snow cover extents, currently ranking as the sixth smallest May snow cover extent. The May Northern Hemisphere snow cover extent is decreasing at an average rate of 4.2 percent per decade. The Northern Hemisphere had its fifth smallest spring (March–May) snow cover extent on record.
The North America snow cover extent was 710,000 square km (270,000 square mi) below average and the 11th smallest May snow cover extent on record. This was also the fourth consecutive May with below-average snow cover extent for North America. Below-average snow cover extent for the month was observed across Alaska and parts of western and eastern Canada, as well as across the Rocky Mountains in the contiguous U.S. Above-average conditions were limited to parts of central and western Canada. Canada and the contiguous U.S. each had their 17th and 18th smallest May extent on record, respectively. Alaska had its ninth smallest on record. The spring 2021 snow cover extent for North America was the sixth smallest for spring on record.
During the month, cooler-than-average temperatures were observed across much of Europe, while much-warmer-than-average temperatures were observed across much of northern Asia. The unusual warmth observed across much of the region contributed to Eurasia's fifth smallest May snow cover extent on record at 7.62 million square km (2.94 million square mi). Below-average snow cover extent was observed across much of northern Russia and across parts of western Mongolia, and western China. Above-average May snow cover extent was limited to Scandinavia, and small areas across southeastern Russia and southwestern China. Eurasia's spring snow cover extent was the eighth smallest on record.
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.
|May 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 May 2021 Arctic sea ice extent was 12.66 million square km (4.89 million square mi), which is 630,000 square km (243,000 square mi)—equivalent to the size of the African country of Somalia—below average. This value ranks as the ninth smallest May sea ice extent in the 43-year record. May 2021 was also the 20th consecutive May with below-average sea ice extent. According to NSIDC, storms during the month across the eastern Arctic helped maintain mild temperatures in the region and spread the ice pack out, resulting in slower-than-average sea ice loss. Sea ice extent was below average across the Baffin Bay, Barents Sea, Bering Sea, Greenland Sea, Hudson Bay, Kara Sea, Laptev Sea, Sea of Japan, and Sea of Okhotsk. Of note, Baffin Bay (tied) and Laptev Sea had their second smallest May sea ice extent on record. Everywhere else had near-average sea ice extent.
The Antarctic sea ice extent for May 2021 was above average at 10.33 million square km (3.99 million square mi)—the largest May sea ice extent since 2015. Overall, the May 2021 sea ice extent tied with 1998 and 2001 as the 16th largest May extent on record. According to the NSIDC, the Antarctic sea ice grew at a slightly below-average pace. Regionally, below-average May sea ice extent was observed across the Weddell and Ross seas.