World of Change: Antarctic Sea Ice

Unlike the Arctic—an ocean basin surrounded by land—the Antarctic is a large continent surrounded by an ocean. Because of this geography, sea ice has more room to expand during the winter. However, that ice also stretches into warmer latitudes, leading to more melting in the summer. Antarctic sea ice usually peaks in September, around the end of the Southern Hemisphere’s winter, and retreats to a minimum in February.

These image pairs show the average concentration of Antarctic sea ice for the month of September (left) and the following February (right) from 1990 to 2026. Opaque white areas indicate the highest concentrations, and dark blue areas are open water. The images include only areas where ice concentration was at least 15 percent, a threshold scientists commonly use to count an area as ice-covered in satellite data. Scientists refer to the total area of these regions as the “sea ice extent.”

According to NASA and the National Snow and Ice Data Center (NSIDC), Antarctic sea ice in 2026 likely reached its annual maximum extent on September 14 (below). On that date, the ice covered an estimated 17.59 million square kilometers (6.79 million square miles), making it the third-lowest maximum on record.

From Record Highs to Record Lows

From 1979 to 2014, total Antarctic sea ice increased by about 1 percent per decade. Whether the increase was a sign of meaningful change is uncertain because ice extents vary considerably from year to year around Antarctica. For three consecutive years, from 2012 to 2014, satellites observed new record highs for winter sea ice extent. These highs occurred while Arctic ice was in steep decline.

The climb came to an end in 2015, and significant decreases in sea ice around Antarctica started to occur in 2016. There have since been years with small rebounds, but overall, Antarctic sea ice coverage has largely remained lower than normal. Both the record low minimum and record low maximum occurred in 2023. 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.

Seeing Through the Clouds

To determine sea ice extent, scientists rely on satellites with passive microwave sensors that measure the microwave energy Earth naturally emits. Sea ice emits more of this energy than open water, so it stands out in microwave images. Because microwaves pass through clouds, the satellites can observe sea ice regularly, regardless of weather.

The record began in late 1978 with data collected by NASA’s Nimbus-7, followed by Defense Meteorological Satellite Program (DMSP) satellites starting in 1987, and by NASA’s Aqua satellite between 2002 and 2011. In 2025, scientists began using observations from the Japan Aerospace Exploration Agency’s GCOM-W satellite. 

Images and story by NASA Earth Observatory, using materials provided by the National Snow and Ice Data Center and NASA's Earth Science News Team. Updated on October 8, 2026.

References & Resources

• NASA Earthdata (2026, October) Sea Ice. Accessed October 8, 2026.
• NASA Earth Observatory (2016, September 16) Sea Ice. Accessed October 8, 2026.
• NASA Earth Science (2026, September 23) Arctic Sea Ice Reaches 2026 Annual Minimum Extent. Accessed October 8, 2026.
• National Snow and Ice Data Center (2026, September 23) Arctic sea ice has reached minimum extent for 2026; Antarctic sea ice maximum most likely reached as well. Accessed October 8, 2026.
• National Snow and Ice Data Center (2026, March 9) Antarctic sea ice extent arrives at a near-average minimum. Accessed October 8, 2026.