Antarctic sea ice reached an annual maximum of 17.59 million square kilometers on September 14, 2026, marking the third-lowest maximum in nearly five decades of satellite records, according to NASA and the National Snow and Ice Data Center.
Polar monitoring programs tracking the planet’s frozen boundaries have recorded another stark milestone as the Southern Hemisphere’s winter drew to a close. Satellite measurements show that the frozen coverage over the Southern Ocean spanned roughly 6.79 million square miles according to data compiled by NASA and the National Snow and Ice Data Center. That footprint covers an area nearly twice the surface of Brazil.
While Antarctica’s sea ice follows a predictable annual rhythm—expanding as temperatures drop and retreating during warmer months—the peak observed on September 14 falls significantly below historical baselines. Researchers use 15 percent ice concentration as the threshold to count a region as ice-covered in satellite imagery. Even with that standard measure, the 2026 winter maximum stands as the third-lowest in the satellite era.
How Satellite Sensors Track the Southern Ocean
Monitoring vast polar regions requires specialized technology capable of operating through storms and darkness. Scientists rely on passive microwave sensors aboard orbiting spacecraft to measure the microwave energy naturally emitted by Earth’s surface. Because sea ice emits more of this energy than open water, it stands out clearly in microwave images regardless of cloud cover.
This continuous observation record stretches back to late 1978. Scientists rely on satellites with passive microwave sensors to identify patterns in sea ice behavior.
Geography and the Shift Since 2015
Antarctica’s physical layout shapes how its ice behaves. Unlike the Arctic, which is an ocean basin surrounded by land, the Antarctic is a continent encircled by the ocean. This geography gives sea ice ample room to expand outward during the winter freeze, but it also exposes the ice to warmer latitudes, where more melting occurs during summer.
Long-term trends in the region have shifted dramatically over the past several decades. From 1979 through 2014, total Antarctic sea ice increased by about 1 percent per decade. During the later years of that period, from 2012 to 2014, researchers recorded some of the highest sea ice levels on record.
The decline began in 2016, and both the record low minimum and record low maximum occurred in 2023. While there have been occasional rebounds, NASA says sea ice coverage has remained below average.
Scientists will continue to observe the area each year to find out if the decline is part of a long-term change or a statistical fluctuation.
NASA, agency report