Antarctica’s sea ice is unlikely to fully recover from its record low cover in 2023, researchers have found. Photo: iStock
The record-shattering low sea ice cover around Antarctica observed in 2023 was an “exceptionally unlikely” event, scientists have confirmed. Researchers analysed data from multiple climate models and found that the extreme ice loss event would have been exceptionally rare, with a chance of one in 2,000 in a world without climate change.
The findings, published in journal Geophysical Research Letters, suggested that the Antarctic sea ice is undergoing a concerning change. It may transition to a new, lower state over the next few decades.
“The [modelling] evidence adds to existing observational evidence that the last few years’ low sea ice could signal a lasting regime shift in the Southern Ocean,” Rachel Diamond, from the British Antarctic Survey and the lead author of the study, told Down To Earth.
Every year, the Southern Ocean around Antarctica freezes to form sea ice, peaking at the end of winter. It reaches its lowest point in February, during the summer months from December to February.
On February 19, 2023, Antarctic sea ice extent hit a new low at 1.77 million square kilometres, which is 1.02 million sq km (36 per cent) less than the average minimum from 1979 to 2022. Satellite records have been kept since 1979.
“Antarctic sea ice is vital for the survival of species like penguins and Antarctic ecosystems and sea ice is one of the key controls of global ocean currents that can impact global climate,” the expert explained. Without sea ice, the ocean absorbs sunlight and gives off heat to the atmosphere, warming it up.
Following the event, scientists debated whether natural variations or climate change were to blame.
So the team turned to global climate models (GCM) to study past sea-ice changes and predict future changes over decades or centuries. A GCM is a complex mathematical representation of the atmosphere, land surface, ocean, sea ice and their interactions.
An analysis of data from 18 different climate models revealed that record low sea ice cover is highly unlikely to have occurred in the absence of climate change.
“Strong climate change — meaning the temperature changes we’re already seeing and those expected if emissions continue to rise rapidly — in the models makes it four times more likely that we see such a big decline in sea ice extent,” Caroline Holmes, the study’s co-author, said in a statement.
Furthermore, the team discovered that Antarctica’s sea ice is unlikely to fully recover from its record low cover in 2023. “The average sea ice extent does recover somewhat over the subsequent years, but it doesn’t completely recover to [its] original levels even after 20 years,” Diamond explained.
On February 20, 2024, Antarctic sea ice reached its minimum extent for the year officially, according to United States’ National Aeronautics and Space Administration. It recorded the second-lowest extent on record, highlighting a trend of declining coverage over time.
Antarctic sea ice has been declining since 2015, following an increase of about a per cent per decade from 1979 to 2014.
Researchers are not sure of what triggered the 2023 event yet. Ocean processes, heat stored beneath the Southern Ocean’s surface and warm sea surface temperatures in the first half of 2023 are thought to be contributing factors. Strong north-to-south winds and storm systems could also have played a role, the researchers speculated.
They argued that it is critical to understand what processes caused the exceptionally low Antarctic Sea ice extent in 2023 and whether this could indicate a long-term regime change in the Southern Ocean.
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