Summary
Antarctic sea ice likely reached its annual maximum on September 14, 2026, covering 17.59 million square kilometres. That was the third-lowest maximum in the satellite record.
Antarctic sea ice likely reached its annual maximum on September 14, 2026, covering an estimated 17.59 million square kilometres (6.79 million square miles). NASA and the National Snow and Ice Data Center (NSIDC) report that this was the third-lowest maximum in the satellite record, which began in 1978.
The figure captures the extent of ice at the end of the Southern Hemisphere winter, not its thickness or total volume. NASA’s account places the 2026 result within a period of sharp year-to-year changes and generally low Antarctic sea-ice coverage.
A low maximum after years of change
Antarctic sea ice expands through winter and usually reaches its maximum in September, then retreats to a minimum in February. The Antarctic is a continent surrounded by ocean, unlike the Arctic, where an ocean is enclosed by land. That geography gives sea ice more room to spread during the Antarctic winter, while also allowing it to extend into warmer latitudes during summer.
The satellite record shows a long period of increase followed by a marked shift. From 1979 to 2014, Antarctic sea ice increased by about 1 percent per decade. Satellites recorded new winter-extent highs in each of three consecutive years, 2012 to 2014. That rise ended in 2015, and substantial decreases began in 2016. Although there have been some smaller rebounds, NASA describes coverage as having remained largely below normal since then. Both the record-low minimum and record-low maximum occurred in 2023.
The 2026 maximum is another low point in that recent sequence. NASA says scientists are continuing to observe the ice each year to determine whether the decline reflects a longer-term change or statistical fluctuation amid substantial year-to-year variability.
How satellites map the ice
Scientists estimate sea-ice extent using passive microwave sensors, which detect microwave energy naturally emitted by Earth. Sea ice emits more of this energy than open water, allowing the two to be distinguished in satellite observations. Microwaves can pass through clouds, so measurements can be collected regularly in different weather conditions.
For this record, an area counts as ice-covered when satellite data indicate a sea-ice concentration of at least 15 percent. Extent is the combined area of regions that meet that threshold; it is therefore a measure of the ice’s geographic footprint, rather than a measurement of how thick the ice is.
The record began with NASA’s Nimbus-7 satellite in late 1978. Defense Meteorological Satellite Program observations followed in 1987, and NASA’s Aqua satellite contributed data from 2002 to 2011. Scientists began using observations from Japan’s GCOM-W satellite in 2025.