Look out over Antarctica in the summer, and time seems frozen. The South Pole's midnight sun appears to hover in place, never dropping below the horizon for weeks between November and January.
Until recently, Antarctic sea ice fluctuated between relatively stable summer minimums and winter maximums. But after a record minimum in 2016, things began to shift. Two record lows soon followed, including the smallest minimum ever in February 2023 at just 737,000 square miles . By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over.Now, in 2024, the sea ice extent has reached another near-record low: just 766,400 square miles on Feb. 20.
The ocean's heartbeatWhen summer turns to winter in the Antarctic, sea ice expands from its minimum of around 1 million square miles to 7 million square miles , covering 4% of Earth's surface in irregular, porcelain-white tiles. Sea ice also helps to drive the conveyor belt of ocean circulation. As sea ice melts, cold water cascading from the continental shelf drives the deep water farther down and out, fueling a circumpolar stream that drives all of the world's ocean currents. In fact, 40% of the global ocean traces its origins to the Antarctic coastline, making it vital in regulating regional climates across the planet.
The Arctic's future has always been simple and bleak: a steady plunge in ice coverage by more than 12% each decade. "If we start losing sea ice annually and the same process occurs in the Antarctic as it does in the Arctic, then the Antarctic will warm at an accelerated rate.” It will be a disaster for the planet," Siegert said.
As sea ice loss tends to occur in regions of high ocean warming, the latter has changed the way the atmosphere and the ocean interact to form ice, shifting the Antarctic system into a new state. It was this change, Purich said, that caused last year's record low. Moreover, the deep ocean currents surrounding Antarctica, which have already slowed by 30% since the 1990s, are predicted to slow by a further 40% by 2050.
The weakening of the Antarctic-driven ocean circulation could also hasten the collapse of key ocean currents, such as the Atlantic meridional overturning circulation , which helps maintain temperate climates in the Northern Hemisphere.