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.

July 2021 Sea Ice Extent
(per decade)
(out of 43 years)
million km2 million mi2 Year(s) million km2 million mi2
Northern Hemisphere 7.69 2.97 -18.80% -7.29% Largest 40th 1983 10.57 4.08
Smallest 4th 2020 7.29 2.81
Southern Hemisphere 16.38 6.32 +2.63% +0.56% Largest 8th 2014 17.11 6.61
Smallest 36th 2017, 2019 15.30 5.91
Globe 24.07 9.29 -5.35% -2.36% Largest 35th 1979 26.83 10.36
Smallest 9th 2019 22.89 8.84

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

The Arctic sea ice extent for July 2021 was the fourth smallest July sea ice extent on record at 1.78 million square km (687,000 square miles) below the 1981–2010 average. Only Julys of 2012, 2019, and 2020 had a smaller sea ice extent in July. July 2021 also marked the 21st consecutive July with below-average sea ice extent. According to the NSIDC, the sea ice extent during July 4–9, 2021 was the lowest extent on record for this time of year; however, afterwards, the rate of sea ice extent loss slowed.

The Antarctic sea ice extent was above average. The July 2021 Antarctic sea ice extent of 16.38 million square km (6.32 million square miles) was 420,000 square km (160,000 square miles) above average. This was the largest July sea ice extent since 2015 and the eighth largest July sea ice extent in the 43-year record. The sea ice extent in the Antarctic grew faster than average during the month. Sea ice was above average across parts of the northeastern Ross Sea and in the Southern Ocean south of Africa.

Citing This Report

NOAA National Centers for Environmental Information, State of the Climate: Monthly Global Snow and Ice Report for July 2021, published online August 2021, retrieved on June 25, 2022 from