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.

June 2021 Sea Ice Extent
(per decade)
(out of 43 years)
million km2 million mi2 Year(s) million km2 million mi2
Northern Hemisphere 10.71 4.14 -9.01% -3.91% Largest 38th 1979 12.53 4.84
Smallest 6th 2016 10.41 4.02
Southern Hemisphere 13.46 5.20 +0.82% +0.75% Largest 16th 2014 14.69 5.67
Smallest 28th 2019 12.25 4.73
Globe 24.17 9.33 -3.78% -1.43% Largest 36th 1979 26.72 10.32
Smallest 8th 2019 22.84 8.82

Data Source: National Snow and Ice Data Center (NSIDC). Period of record: 1979–2021 (43 years)

The Arctic sea ice extent for June 2021 was 10.71 million square km (4.14 million square miles), which is 1.05 million square km (405,000 square miles) — about the size of the South American country of Paraguay — below the 1981–2010 average. This value ranks as the sixth-smallest June sea ice extent in the 43-year record. According to the NSIDC, the pace of Arctic sea ice loss during June 2021 was faster than average, with an average ice loss of 79,600 square km (30,700 square miles). June 2021 marked the 22nd consecutive June with below-average sea ice extent. The Arctic's ten smallest June sea ice extents have occurred since 2010.

Antarctic sea ice extent during June 2021 was above average and the largest for June since 2015 at 13.46 million square km (5.20 million square miles). During the month, sea ice grew at a slightly above-average pace. Sea ice extent was below average across the Bellingshausen Sea and the northwestern Weddell Sea, while sea ice extent was above average across the Ross and Amundsen seas.

Citing This Report

NOAA National Centers for Environmental Information, State of the Climate: Global Snow and Ice for June 2021, published online July 2021, retrieved on September 22, 2021 from