Antarctic Sea Ice Peaked at Its Third-Lowest Level, Then Melted to a Record Low for Early October

Keypoints:

• Antarctic sea ice reached its maximum of 17.59 million square kilometres on 14 September
• That is the third-lowest winter peak in the satellite record, about 1 million square kilometres below average
• The four lowest winter maximums have all occurred in the past four years
• Daily extent in early October set a record low for that time of year
• Arctic sea ice tied for its 10th-lowest summer minimum on 12 September

Sea ice around Antarctica reached its annual maximum on 14 September 2026, according to NASA and the National Snow and Ice Data Center (NSIDC). The ice covered about 17.59 million square kilometres. That is the third-lowest winter peak since satellite records began in 1978. It sits about 1 million square kilometres below the long-term average maximum, an area roughly twice the size of Spain.

The trend is a sharp reversal. From 1979 to 2014, Antarctic sea ice grew by about 1% per decade. The winter maximum set new records in three straight years from 2012 to 2014. The trend then turned around in 2015, and ice cover has fallen substantially since 2016. The lowest summer minimum and the lowest winter maximum both came in 2023. The four lowest winter maximums have occurred in the last four years.

Antarctica's geography explains its behavior. A continent surrounded by open ocean gives sea ice room to spread far in winter. It also pushes the ice into warmer latitudes, where melting is more likely in summer. Extent usually peaks in September and falls to a minimum in February. Scientists count an area as ice-covered when at least 15% of the ocean surface is frozen.

The melt this year was fast. Once the winter peak passed, ice retreated rapidly as spring arrived. By early October, daily extent dropped below the record low for that date, set in 2023, according to NSIDC.

Scientists disagree about the cause. Walt Meier of NSIDC says four record-low winters in a row point to a system that has changed. Ted Scambos of the Cooperative Institute for Research in Environmental Sciences cautions that it is still hard to be sure how global warming affects Antarctic sea ice, because the ice varies a lot from year to year.

At the other pole, Arctic sea ice reached its annual minimum of about 4.60 million square kilometres on 12 September. That tied for the 10th-lowest in the satellite record. Will the Southern Ocean keep setting records, or is this a long swing that will reverse?