Antarctic Sea Ice Reaches Third Lowest 2026 Maximum Extent

Antarctic sea ice likely reached its annual maximum extent on September 14, 2026, covering an estimated 17.59 million square kilometers, according to NASA and the National Snow and Ice Data Center. The measurement marked the third-lowest maximum recorded since satellite observations began.

The annual peak occurred near the end of the Southern Hemisphere winter, when Antarctic sea ice typically reaches its largest area before retreating toward its February minimum, according to NASA.

NASA reported that Antarctic sea ice extent is measured using satellite observations of ice-covered regions with at least 15 percent ice concentration. The threshold is used by scientists to define the area counted as sea ice extent.

The Antarctic differs from the Arctic because it is a continent surrounded by ocean rather than an ocean basin surrounded by land. This geography allows sea ice to expand during winter but also exposes it to warmer latitudes where melting increases during summer.

NASA said Antarctic sea ice increased by about 1 percent per decade from 1979 through 2014, although yearly changes varied considerably. Satellite records showed record winter highs from 2012 to 2014 before major declines began in 2016.

Both the record low minimum and record low maximum Antarctic sea ice extents occurred in 2023, according to NASA. Scientists continue monitoring annual changes to determine whether recent declines represent a long-term shift or natural variation.

NASA uses passive microwave sensors aboard satellites to track sea ice because microwaves can pass through clouds and allow observations regardless of weather conditions. The record began in late 1978 with NASA's Nimbus-7 satellite.

Satellite data have also come from Defense Meteorological Satellite Program satellites starting in 1987, NASA's Aqua satellite between 2002 and 2011, and observations from the Japan Aerospace Exploration Agency's GCOM-W satellite beginning in 2025.