Climate change may be to blame for historic Antarctica sea ice loss, study finds

Record low levels of sea ice around Antarctica last year could be linked to climate change, a study has found. Researchers at the British Antarctic Survey (BAS) found the continent’s historically low sea-ice levels were a one-in-2,000-year event without climate change – but four times more likely under its effects. They studied 18 climate models to conclude that the event was “very extreme”. Rachel Diamond, lead author of the paper published in the Geophysical Research Letters journal, told The National sea ice loss last year was “unprecedented” in the satellite record, which stretches back 45 years. The team used models to work out how likely the sea-ice loss was and whether climate change made it more likely. “We found that the 2023 Antarctic sea ice loss was a very rare event. According to the models, we expect to see it less than once-in-2,000 years without climate change. “We found that strong climate change, in line with what we have been seeing and what we might expect to see in the future without mitigation, increases the chances of the sea ice loss we saw to being a one-in-500-year event. “One in 500 years is still very rare but the results do suggest that climate change made the 2023 loss more likely.” She added: "This tells us that the event was very extreme. Anything less than one in 100 is considered exceptionally unlikely." The study also suggested the record loss could have a lasting impact. “We found that after such extreme sea ice loss, not all of the sea ice around Antarctica recovers, even after 20 years. “That tells us that even if we see sea ice beginning to recover over the next few years, it still might on average stay relatively low for decades.” This would affect penguins, whales and other animals that rely on the ice for their habitat, the researchers said. Louise Sime, a co-author of the study, said: "The impacts of Antarctic sea ice staying low for over 20 years would be profound, including on local and global weather and on unique Southern Ocean ecosystems, including whales and penguins." Antarctica , the world’s fifth largest continent, is about 50 times the size of the UK. In 2023, Antarctic sea ice reached record-low levels, with more than 2 million square kilometres less ice than usual during winter – about 10 times the size of the UK. Until 2015, Antarctica's winter sea ice had been growing in size since satellite records began in 1978. Antarctica's vast expanse of sea ice regulates Earth's temperature, as the white surface reflects the Sun's heat into the atmosphere and cools the water beneath it. Without it, the planet would be a much hotter place. Last year a scientific study found that almost half of Antarctica ’s ice shelves have shrunk in the past 25 years, suggesting human-induced global warming was a possible cause. Researchers at the University of Leeds found that 71 of the 162 ice shelves that surround the continent in the Southern Hemisphere reduced in volume from 1997 to 2021, releasing 7.5 trillion tonnes of meltwater into the oceans. Almost all the ice shelves on the western side of Antarctica , which is exposed to warm water, became smaller, while those on the more protected eastern side stayed the same size or increased in volume, it said. Ice shelves, which float on the seas surrounding Antarctica , act as giant “plugs” at the end of glaciers, slowing down the flow of ice draining into the oceans. If they weaken or reduce in size, the rate of ice lost from the glaciers increases.