Antarctica is experiencing a dramatic convergence of climate extremes this winter: an area of sea ice the size of France has failed to form along the continent's west coast, while temperatures at a research base on the Antarctic Peninsula broke all previous records by a significant margin. Scientists are warning of serious consequences for ecosystems, glaciers, and global sea levels.

Satellite data shows that the Bellingshausen Sea — a body of water on the western side of the Antarctic Peninsula — is almost entirely ice-free, despite June being the heart of the Southern Hemisphere winter, when sea ice normally expands rapidly. The region is missing roughly 650,000 square kilometres of ice compared with the 1991–2020 average, nearly ten times the size of the Australian state of Tasmania. Across the whole continent, sea ice coverage stood at 11.4 million square kilometres on 10 June, well below the long-term average of 12.6 million square kilometres for that date. "I don't think we will see sea ice there any more. It's done," said Dr Will Hobbs, an Antarctic sea ice expert at the University of Tasmania, describing the situation as "depressing." He noted this is the third time in four years that ice coverage in the region has fallen to such extreme lows.

At the same time, Argentina's Esperanza research base, situated at the northeastern tip of the Peninsula, recorded a maximum temperature of 15.4°C on 5 June — more than 20°C above the seasonal average of -6.2°C and breaking a record that had stood since 1998. Researchers on nearby King George Island reported that the landscape had shifted from predominantly white to brown, grey, and green as snow and ice melted under persistent above-freezing temperatures and unusually heavy rainfall. Chilean glaciologist Luis Muñoz observed that rain was actively melting the Collins Glacier, which should normally be accumulating new snow at this time of year.

The absence of sea ice is compounding these problems in several ways. Sea ice typically acts as a buffer, cooling warmer air masses flowing in from the north; without it, heat events over the Peninsula can intensify. More critically, floating ice shelves in front of the Pine Island and Thwaites glaciers — two of Antarctica's largest contributors to sea level rise — may break up more quickly if protective sea ice remains absent for extended periods, potentially accelerating ice loss from the glaciers themselves. The Bellingshausen Sea is also vital habitat for krill, which shelter under ice in winter, grazing on algae; their decline ripples through an entire food web. Emperor penguins, already reclassified as "endangered" following a catastrophic 2022 breeding failure in the same region that killed thousands of chicks, face renewed pressure as sea ice forms too late and breaks up too early.

While scientists are cautious about attributing any single event directly to climate change — British polar researcher Thomas Caton Harrison noted that Antarctica's unique ocean currents and wind patterns make the fingerprint of global warming harder to detect there than elsewhere — he said there is "credible evidence that climate change is playing a role." The broader global context is stark: the past three years have been the warmest on record worldwide. Researchers stress that sustained, long-term monitoring is essential to fully understand what is unfolding at the bottom of the world, even as its ecosystems are already visibly changing.