For decades, Antarctica seemed to defy global warming. Since satellites began monitoring the poles in the late 1970s, the seasonal growth and retreat of Antarctic sea ice – frozen seawater that expands around the continent each winter – appeared remarkably resilient. It was often described as the “heartbeat of the planet”.

Unlike the Arctic, where sea ice declined rapidly as the planet warmed, Antarctic sea ice showed little overall loss. It even expanded between 2007 and 2015. But that resilience has now broken.

Since 2015, Antarctic sea ice has declined sharply. In 2023, winter sea ice extent fell to record lows — so far below the long-term average that scientists considered it an event with roughly a one-in-3.5-million probability of occurring by chance.

Antarctica was long considered a part of the climate system expected to change slowly. The speed of the recent sea ice decline has therefore come as a shock.

Scientists did........

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