Antarctica and Earth's climate

Antarctica loses more heat to space than it receives from the Sun. White snow reflects most sunlight, the air is very dry and the plateau is high, so the continent acts as the southern hemisphere's major cooling center. It also holds the planet’s cold-weather records, collected in The extremes of the Earth.

The temperature difference between Antarctica and the tropics drives winds and currents that carry heat from the equator to high latitudes. The westerly winds that circle the continent, blowing over ocean with no land barriers, are part of that system.

That is why changes in Antarctica do not stay there: they alter ocean circulation, sea level along coasts worldwide and weather on southern continents.

According to Bedmap3 mapping, coordinated by the British Antarctic Survey and published in 2025, Antarctica's ice sheet contains about 27 million cubic kilometers of ice. If it melted entirely, it would raise sea level by about 58 meters. The IPCC projections for this century are much lower than that, but the figure shows the size of the stockpile.

Only ice grounded on land raises sea level when it melts. Sea ice and floating ice shelves are already afloat and barely change sea level, like an ice cube in a glass. But ice shelves buttress the glaciers behind them: when they break up, those glaciers accelerate toward the ocean, as described in Antarctic ice.

Most of the ice lies in East Antarctica, much of it over bedrock above sea level. In West Antarctica, much ice rests on bedrock below sea level, which makes it more exposed to warmer ocean waters.

The GRACE satellites, a NASA partnership with the German space agency, from 2002 to 2017, and GRACE Follow-On, since 2018, measure tiny variations in Earth's gravity that reveal how much ice the continent gains or loses. According to NASA, between 2002 and 2025 Antarctica lost on average about 135 billion tonnes of ice per year, raising sea level by about 0.4 millimeter per year.

Loss is not uniform across the continent. West Antarctica and the Peninsula are losing ice, especially in the Pine Island and Thwaites glaciers, which drain into the Amundsen Sea. Parts of East Antarctica have gained some mass from increased snowfall, but not enough to compensate.

IMBIE, an international group that compares measurements from multiple satellites, calculated in 2018 that Antarctica lost about 2,700 billion tonnes of ice between 1992 and 2017, equivalent to 7.6 millimeters of sea-level rise, and that the annual loss tripled from 2012 onward.

Numbers vary between studies, depending on method and period, and from year to year with snowfall. What measurements commonly show is ice loss over recent decades.

Sea ice around Antarctica grows and shrinks every year. According to the 1981–2010 average from NSIDC, the U.S. snow and ice data center, it reaches about 18.7 million square kilometers in September and falls to about 2.8 million in February.

Until 2015, its extent remained stable and even increased slightly, unlike the Arctic. From 2016 it declined: the minimum of February 21, 2023, at 1.79 million square kilometers, was the smallest since satellite records began in 1978, and the maximum of September 2023 was also the smallest on record.

The minima of 2022, 2024 and 2025 are tied as the second smallest, near 1.98 million square kilometers. In 2026 the minimum, on February 26, rose to about 2.58 million, still below the average.

Scientists continue to debate the contribution of factors such as warmer subsurface ocean waters, winds and natural variability. With less sea ice, the ocean absorbs more solar heat, and ice shelves and emperor penguin colonies, which rely on ice to raise chicks, become more exposed.

The ozone layer, between about 15 and 35 kilometers altitude, filters part of the Sun's ultraviolet radiation. In May 1985 Joe Farman, Brian Gardiner and Jonathan Shanklin of the British Antarctic Survey published Halley station measurements showing that each spring ozone over Antarctica dropped dramatically.

The cause is chlorine and bromine released by substances such as CFCs, used in refrigerators, aerosols and foams. In winter, extreme cold forms clouds in the polar stratosphere; when the Sun returns in September and October, reactions on those clouds destroy ozone. That is why the hole appears in the southern spring and closes by year’s end.

The Montreal Protocol, of September 16, 1987, gradually eliminated those substances and is one of the few treaties ratified by every country.

According to NASA and NOAA, the 2025 ozone hole was the fifth smallest since 1992, averaging 18.71 million square kilometers between September 7 and October 13, and began to recover almost three weeks earlier than the decade’s recent norm. The World Meteorological Organization assesses that the Antarctic ozone layer should return to 1980 levels around 2066 if current rules are maintained.

The Antarctic Circumpolar Current flows from west to east around the continent, with no land in its path, and links the Atlantic, Indian and Pacific oceans. It helps keep Antarctica isolated from warmer waters to the north, as described in Geography of Antarctica.

Near the coast, when seawater freezes the salt is left behind in the remaining water, which becomes denser and sinks. This very cold, salty water — Antarctic Bottom Water — spreads along the ocean floor as far as the Northern Hemisphere and drives a circulation that takes centuries to circle the planet.

The Southern Ocean also stores heat and carbon. Studies using measurements and models indicate that the ocean south of latitude 30°, which covers about 30% of the ocean area, accounts for roughly 40% of the human-caused carbon dioxide absorbed by the oceans and about three quarters of the excess heat they take up.

For that reason, changes in the amount of ice and freshwater at the Antarctic coast are closely monitored: they can alter bottom water formation and the strength of that circulation.

Antarctica was not always frozen. Around 90 million years ago there were forests near the South Pole, and fossils of dinosaurs, plants and marsupials have been found on the continent.

Permanent ice began to cover the continent about 34 million years ago, when atmospheric carbon dioxide declined and seaways opened between Antarctica, South America and Australia, allowing the circumpolar current to isolate the continent.

Ice cores show that over the past 800,000 years atmospheric carbon dioxide varied between about 180 and 300 parts per million, tracking the glacial cycles. According to NOAA, the global average for 2024 rose above 420 parts per million.

Numbers about Antarctica change with each new measurement and vary considerably from year to year. A single summer with little sea ice or a year with heavy snowfall does not by itself indicate a trend; what matters are multi-decade time series.

Satellite measurements began in 1978 for sea ice and in the early 1990s for ice-sheet elevation. To separate natural variability from human-caused warming, scientists combine these series with ice-core records, marine sediments and models.

The most used datasets are public and come from NASA and NOAA, the NSIDC, the British Antarctic Survey, the World Meteorological Organization and the IPCC reports, which compile published science from around the world.