NOAA's National Centers for Environmental Information
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.
| August 2021 | Sea Ice Extent | Anomaly 1991-2020 | Trend per decade | Rank (43 years) | Record | ||||
|---|---|---|---|---|---|---|---|---|---|
| million km² | million mi² | Year(s) | million km² | million mi² | |||||
| Northern Hemisphere | 5.71 | 2.20 | -11.20% | -11.35% | Largest | 34th | 1983 | 8.19 | 3.16 |
| Smallest | 10th | 2012 | 4.72 | 1.82 | |||||
| Southern Hemisphere | 18.19 | 7.02 | +1.96% | +0.50% | Largest | 5th | 2014 | 18.91 | 7.30 |
| Smallest | 39th | 1986 | 17.00 | 6.56 | |||||
| Globe | 23.90 | 9.23 | -1.52% | -2.64% | Largest | 32nd | 1982 | 25.93 | 10.01 |
| Smallest | 12th | 2019 | 22.51 | 8.69 | |||||
Data Source: National Snow and Ice Data Center (NSIDC). Period of record: 1979–2021 (43 years)
Sea ice loss during August 2021 was near average; however, it was slower than recent years. The August 2021 Arctic sea ice extent averaged 5.75 million square km (2.22 million square miles), which is 1.45 million square km (560,000 square miles) below the 1981–2010 average. This was the 10th-smallest August extent in the 43-year record; however, it was the largest August sea ice extent since 2014. August 2021 marked the Arctic's 20th consecutive August with below-average sea ice extent. NSIDC stated that the loss of ice across the Arctic since records began in 1979 is about twice the size of the U.S. state of Alaska.
The Antarctic sea ice extent was once again above average. The August 2021 Antarctic sea ice extent of 18.13 million square km (7.0 million square miles) was 410,000 square km (160,000 square miles) above average. This was the largest August sea ice extent since 2014 and the fifth largest August sea ice extent in the 43-year record. Sea ice was above average across the Weddell and Cosmonaut seas.