Antarctica is being overwhelmed by a triple whammy of climate chaos that has driven sea ice to record lows, a new study has revealed. For decades, the frozen wilderness at the South Pole defied global warming trends, with ice continuing to grow until 2015, when it suddenly reversed. Now, scientists believe they have discovered why.
Compounding Events Ravage the Continent
Experts say a series of compounding events have ravaged the continent, including strengthening winds that pull warm water to the surface. These have been so extreme that vast amounts of ice equivalent to the size of Greenland have been wiped out, leading to record-breaking lows in 2023.
Dr Aditya Narayanan, lead author from the University of Southampton, said Antarctic sea ice helps drive a crucial ocean current system known as AMOC. He stated: '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.'
Three Stages of Sea Ice Decline
The study, published in Science Advances, was undertaken by 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.
- Stage 1 (around 2013): Strengthening winds began pulling warm, salty water from the deep ocean closer to the surface.
- Stage 2 (2015): Intense winds mixed the deeper heat directly into the surface layer, rapidly melting sea ice, particularly in East Antarctica.
- Stage 3 (since 2018): The ice-ocean system has become trapped in a cycle where, with less ice to melt, the surface remains salty and warm, preventing new ice from forming.
The scientists also found a significant imbalance in how the ice is retreating across the continent. East Antarctic ice loss is 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 melted the sea ice during the summers of 2016 and 2019.
Global Consequences
'This isn't just a regional problem – Antarctic sea ice acts as Earth's mirror, reflecting solar radiation back into space,' co-author Dr Alessandro Silvano said. '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 team also warned that human-driven climate change is fuelling stronger winds, exposing the Southern Ocean's surface and pushing deep-sea heat upwards. 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.'
Study Conclusions
The study concludes: 'We have shown that Antarctic sea ice loss in recent years was the compound result of a range of drivers acting in three distinct phases. This has led to a sustained low sea ice state unprecedented in the observational record. There is good reason to believe that upwelling-favourable conditions…are likely to persist under the influence of greenhouse gas emissions and the ozone hole.'
Related Concerns: Ice Shelves at Risk
Earlier this week, a separate group of experts warned that rapidly melting ice shelves in Antarctica could trigger global sea levels to rise even faster than expected. Antarctica's vast floating ice shelves surround about 75 per cent of the continent's coastline and act like a vast buttress, holding back the flow of inland glaciers. However, Norwegian researchers have discovered that deep channel-like grooves beneath the ice are trapping swirling eddies of relatively warm ocean water. That warm water melts ice beneath the surface 10 times faster than normal, threatening the structural integrity of the entire ice shelves.
Lead author Dr Qin Zhou, senior scientist for Norwegian research organisation Akvaplan-niva, told the Daily Mail: 'These ice shelves may be more vulnerable to ocean warming than previously assumed. If the Antarctic shelves were significantly weakened or even started to collapse, it would release the gigatonnes of ice currently being held back in the ice sheet.' The ice sheet currently holds enough fresh water to raise sea levels by a staggering 58 meters (190 feet), threatening millions of people with flooding. While the researchers don't think the entire ice sheet will melt, they warn that sea levels are likely to be a lot higher than previous climate models have predicted.
Antarctica's ice sheets contain 70 per cent of the world's fresh water, and if all the ice sheets were to melt due to global warming, Antarctica would raise global sea levels by at least 183 feet (56 metres). Given their size, even small losses in the ice sheets could have global consequences. In addition to rising sea levels, meltwater would slow down the world's ocean circulation, while changing wind belts may affect the climate in the southern hemisphere.
