Antarctica briefing

Warming and Circulation

Last reviewed October 13, 2026

Antarctica is not warming in one simple, uniform pattern. The peninsula, West Antarctica, the high interior, the atmosphere above them, and the ocean around them can change at different rates. The larger signal is nonetheless clear: human-added heat has entered the coupled atmosphere–ocean system, and the Southern Ocean has absorbed and redistributed an exceptional share of it.

The ocean is the main heat reservoir

The ocean has absorbed most of the excess heat accumulating in the Earth system. A 2024 modelling study reported by the British Antarctic Survey estimated that the Southern Ocean accounted for 83 ± 33% of global ocean heat uptake over the historical period. The broad uncertainty matters, but so does the scale: a region covering about one-fifth of the global ocean has been a dominant heat sink.

That historical share is not a fixed law. The same study projected a smaller Southern Ocean share as aerosol and greenhouse-gas forcing evolve, while the region remains important to both heat and carbon uptake. Past uptake has moderated atmospheric warming while committing the ocean and ice shelves to long-lived change.

The Antarctic Circumpolar Current flows around the continent and connects the Atlantic, Pacific, and Indian oceans. Water masses formed or transformed in the south carry heat, carbon, oxygen, and nutrients through the global ocean. That is why an Antarctic change can be remote in geography and global in consequence.

Sea ice: a summer rebound and a low winter maximum

Antarctic sea ice expands and contracts dramatically each year. Unlike land ice, its melting does not materially raise sea level. It does influence the exchange of heat between ocean and atmosphere, the formation of dense water, habitat, and the timing of biological productivity.

The 2026 summer minimum reached 2.58 million square kilometres on February 26, according to the National Snow and Ice Data Center’s March 9 report. It ranked sixteenth lowest in the 48-year satellite record: still 260,000 square kilometres below the 1981–2010 average, but 730,000 square kilometres above the record low set in 2023.

The September maximum

The winter result was less reassuring. In its October 12 account, NASA reported that Antarctic sea ice likely reached its annual maximum on September 14, 2026, at an estimated 17.59 million square kilometres. That was the third-lowest annual maximum in the satellite record. This is the seasonal peak, not the average extent across September.

NSIDC’s October 7 analysis also described a sharp retreat after the maximum and exceptionally low daily extents in early October. That is a dated account of the start of the melt season, not a live reading or a forecast of the next summer minimum.

The February and September results are not contradictory. One measures how little ice remained after summer; the other measures how far the cover grew through winter. A less extreme minimum did not guarantee a normal growth season. Neither result, by itself, settles the long-term trajectory. Researchers are testing whether the post-2016 decline reflects a lasting structural shift in the atmosphere–ocean–sea-ice system.

Circulation and weather

Antarctic conditions interact with winds, ocean fronts, and atmospheric waves that extend beyond the continent. Those connections are real, but simple claims that a particular Antarctic change “caused” a particular distant storm or heat wave usually run ahead of attribution science.

Some relationships are better established than others. Changes in Southern Hemisphere westerly winds affect ocean upwelling and the location of major fronts. Ozone depletion and greenhouse forcing have both influenced those winds. The downstream effects vary by season, region, and timescale. Responsible interpretation states the mechanism without pretending that every link is equally settled.

What is known—and what is not

Known: the Southern Ocean has been a dominant reservoir for human-added heat; warm water reaching continental shelves can increase basal ice-shelf melt; and Antarctic sea ice has experienced several exceptional lows since

  1. The relatively near-average February 2026 minimum was followed by the third-lowest winter maximum in the satellite record.

Still uncertain: whether the recent sea-ice regime will persist, how Southern Ocean circulation will reorganize, and the strength of particular links to regional weather outside Antarctica.

Primary sources