Summary:
Antarctic sea ice loss has been driven by a combination of deep ocean warming, intensified winds and long-term ocean changes that pushed the Southern Ocean into a prolonged low sea ice state, according to a study published in Science Advances. Researchers led by the University of Southampton found that the sharp decline in sea ice since 2015 followed three connected phases that progressively weakened the region’s ability to recover ice cover.
Using an observationally constrained sea ice and ocean model covering 2013 to 2023, the team found that stronger westerly winds first drew warm, salty Circumpolar Deep Water (CDW) closer to the surface. Intense wind-driven mixing in 2015 and 2016 then transferred that heat into upper ocean layers, triggering rapid ice melt, particularly in East Antarctica. Since 2018, reduced freshwater export from sea ice has helped maintain warmer and saltier surface waters, limiting large-scale ice recovery.
The study also identified regional differences across Antarctica. In East Antarctica, sea ice decline was mainly driven by subsurface ocean warming, while in West Antarctica atmospheric heat linked to cloud cover and warm subtropical air also contributed to melting. The researchers warn that continued human-driven climate forcing could keep the Southern Ocean in a prolonged state of reduced sea ice coverage.
— Press Release —
Antarctic sea ice collapse driven by triple whammy of climate chaos, scientists find
For decades, the frozen wilderness at the bottom of the world defied global warming trends, with ice levels actually growing – until 2015 when it suddenly reversed.
Now scientists say they have discovered why.
The study led by the University of Southampton shows that a series of compounding events flipped the Southern Ocean – which surrounds Antarctica – out of balance, dragging unusually warm, salty water from the deep up to the surface.
It was so extreme, said lead author Dr Aditya Narayanan, that it wiped out vast areas of ice equivalent to the size of Greenland, leading to record-breaking lows in 2023.
Dr Narayanan, an oceanographer from the University Southampton, added: “Antarctic sea ice in the Southern Ocean helps drive the planet’s ocean overturning circulation.
“However, since 2015, the region has undergone a huge transformation, with extreme ice loss around the continent.
“What started as a slow build-up of deep-sea heat under the Antarctic sea ice was followed by a violent mixing of water, ending in a vicious cycle where it’s too warm to let ice recover.
“It’s concerning because massive loss of sea ice destabilises the world’s ocean current systems, warming our planet far quicker than expected.”
The study, published in Science Advances, was undertaken by the Southampton experts working with scientists worldwide.
Using a sophisticated ice-measuring programme, the team found the sea ice decline happened in three stages, driven by shifting winds and warming oceans.
- Around 2013 – strengthening winds began pulling warm, salty water from the deep ocean, known as Circumpolar Deep Water, closer to the surface;
- In 2015 – intense wind mixed the deeper heat directly into the surface layer, rapidly melting sea ice, particularly in East Antarctica;
- Since 2018 – the ice-ocean system has become trapped in a cycle where, with less ice to melt, the surface remains salty and warm, inhibiting new ice from forming.
The study also found a striking asymmetry in how the ice is retreating across the continent, with East Antarctic loss almost entirely ocean-driven, fuelled by an upward surge of warmer deep water.
However, in West Antarctica, heat was trapped in the ocean by intense cloud cover, which was funnelled by warm air from the subtropics down to the pole, melting the sea ice during the summers of 2016 and 2019.
Paper co-author Dr Alessandro Silvano, also from the University of Southampton, said: “This isn’t just a regional problem, Antarctic sea ice acts as Earth’s mirror, reflecting solar radiation back into space.
“Its loss could destabilise the currents that store heat and carbon in the ocean, accelerating global warming, and also destabilise ice shelves that prevent glaciers from sliding into the sea, raising global sea levels.”
The Southampton-led research team also warned human-driven climate change is fuelling stronger winds, exposing the Southern Ocean’s surface and pushing deep-sea heat to the surface.
If this continues, the Southern Ocean could be pushed into a “prolonged low sea-ice state,” said Professor in Physical Oceanography Alberto Naveira Garabato from the University of Southampton.
He added: “If the low sea-ice coverage prevails into 2030 and beyond, the ocean may transition from a stabiliser of the world’s climate to a powerful new driver of global warming.”
Journal Reference:
Aditya Narayanan, Holly Ayres, Matthew H England, Alexander Haumann, Matthew R, Mazloff, Alessandro Silvano, Theo Spira, Shenjie Zhou & Alberto C. Naveira Garabato, ‘Compound drivers of Antarctic sea ice loss and Southern Ocean destratification’ , Science Advances 12, 19: eaeb0166 (2026). DOI: 10.1126/sciadv.aeb0166
Article Source:
Press Release/Material by James Haigh | University of Southampton
Featured image credit: Hugo Sykes | Pexels
