Antarctic sea ice reached its annual winter peak in September 2026, but the ice covered less ocean than in nearly any other year since satellite measurements began. Its maximum extent was the third lowest on record, adding to growing evidence of a dramatic shift in Antarctica's frozen waters. Antarctica is surrounded by a vast ocean, giving its sea ice plenty of room to spread outward during the Southern Hemisphere's winter.
This differs from the Arctic, where an ocean basin is enclosed by surrounding land. Although Antarctica's geography allows winter sea ice to expand over enormous distances, it also pushes the ice into warmer latitudes, where melting becomes more likely during summer. As a result, Antarctic sea ice generally reaches its largest extent in September before shrinking to its annual minimum in February.
According to NASA and the National Snow and Ice Data Center (NSIDC), Antarctic sea ice likely reached its annual maximum extent on September 14 (above). At its peak, the ice stretched across approximately 17.59 million square kilometers (6.79 million square miles). That made 2026 the year with the third-lowest winter maximum in the satellite record.
The maps below illustrate how Antarctic sea ice changes between seasons, showing average ice concentrations in September (left) and the following February (right) from 1990 to 2026. Solid white regions represent areas with the greatest ice coverage, while dark blue indicates open ocean. Only locations where ice covers at least 15 percent of the water are included.
Scientists use this threshold to determine which areas qualify as ice-covered when calculating the total "sea ice extent." Antarctic Sea Ice Shifts From Record Growth to Historic Lows For decades, Antarctic sea ice appeared to be moving in the opposite direction from the rapidly shrinking ice in the Arctic. Between 1979 and 2014, sea ice extent around Antarctica increased by approximately 1 percent per decade. However, because Antarctic ice coverage naturally fluctuates considerably from year to year, researchers remain uncertain whether this gradual increase reflected a meaningful long-term change.
The expansion became particularly noticeable between 2012 and 2014, when Antarctic winter sea ice set new record highs for three consecutive years. These records stood in stark contrast to conditions at the opposite pole, where Arctic sea ice was undergoing a steep decline. But Antarctica's upward trend ended in 2015.
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