Antarctic sea ice reached its annual maximum extent on September 14, 2026 recording the third lowest peak in the satellite observation record according to NASA and the National Snow and Ice Data Center (NSIDC). The ice covered an estimated 17.59 million square kilometres (6.79 million square miles) highlighting the continued changes in sea ice conditions around the continent.
Antarctic sea ice typically reaches its maximum in September towards the end of the Southern Hemisphere’s winter before retreating to its minimum extent in February. Unlike the Arctic, which is an ocean basin surrounded by land, Antarctica is a continent surrounded by the Southern Ocean. This geography allows sea ice to expand over a large area during winter although the ice also extends into warmer latitudes, where it melts during summer.
NASA’s Earth Observatory reported the 2026 maximum in an update to its World of Change series, which tracks long term changes on Earth’s surface using satellite observations. The accompanying map shows the distribution of sea ice on September 14, with the median extent for 1981–2010 outlined for comparison.
From Record Highs to Record Lows
Antarctic sea ice extent followed a generally increasing trend between 1979 and 2014 growing by approximately 1 per cent per decade. However scientists have cautioned that the significance of this increase remains uncertain because Antarctic sea ice varies considerably from year to year.
The period included three consecutive years of record high winter sea ice extent from 2012 to 2014, even as Arctic sea ice was experiencing a steep decline.
The trend changed in 2015 followed by substantial decreases in Antarctic sea ice beginning in 2016. Although some years have recorded modest rebounds, sea ice coverage has largely remained below normal levels in recent years.
Both the record low minimum and record-low maximum extents occurred in 2023. The 2026 maximum while higher than the record low, remained the third lowest in the satellite record.
Scientists continue to monitor Antarctic sea ice to determine whether the recent decline represents a longer term shift or reflects natural fluctuations in the region’s highly variable ice conditions.
How Satellites Measure Sea Ice
Scientists use satellites equipped with passive microwave sensors to measure sea ice extent. These instruments detect microwave energy naturally emitted by Earth. Because sea ice emits a different amount of this energy than open water scientists can distinguish ice covered areas even when clouds obscure the surface.
The measurements include areas where sea ice concentration reaches at least 15 per cent, a threshold commonly used by researchers to classify a region as ice-covered. The total area of these regions is known as sea ice extent.
The satellite record began in late 1978 with observations from NASA’s Nimbus-7 satellite. Defence Meteorological Satellite Program satellites began contributing data in 1987, followed by observations from NASA’s Aqua satellite between 2002 and 2011. Since 2025, scientists have also used observations from the Japan Aerospace Exploration Agency’s GCOM-W satellite.
These long running observations allow researchers to compare sea ice conditions across decades and identify changes in seasonal patterns.
Scientists Continue to Monitor Long Term Changes
NASA and NSIDC will continue tracking Antarctic sea ice each year to assess whether recent low levels persist. The data provide an important record of changes in the Southern Ocean and help scientists study the relationship between sea ice ocean conditions and the wider climate system.
The 2026 maximum adds to a period of unusually low Antarctic sea ice coverage following the sharp declines that began in 2016. However scientists say continued observations are necessary to establish whether these changes indicate a lasting shift in Antarctic sea ice behaviour or part of the region natural variability.