An ice-free Arctic is possible by the summer of 2027, even earlier than previous pessimistic predictions by climate scientists.
Arctic ice is shrinking at an unprecedented rate of 12 per cent every 10 years due to greenhouse gas emissions, potentially leading to its first ice-free day before the end of the decade. Such an event is expected to significantly alter the Earth's ecosystem and lead to more extreme weather.
Scientists at the University of Boulder Colorado in the US and the University of Gothenburg in Sweden used computer modelling to predict when the first ice-free day could occur. They carried out hundreds of computer simulations and found that, while still unlikely, an ice-free day was possible in the next three to six years as global air temperatures rise. The findings were published on Tuesday in the journal Nature Communications.
“The first ice-free day in the Arctic won’t change things dramatically,” said Alexandra Jahn, associate professor in the Department of Atmospheric and Oceanic Sciences and fellow at CU Boulder’s Institute of Arctic and Alpine Research. “But it will show that we've fundamentally altered one of the defining characteristics of the natural environment in the Arctic Ocean, which is that it is covered by sea ice and snow year-round, through greenhouse gas emissions.”
The team's previous analysis published in March found that the ice-free milestone could occur sometime in the mid-2030s. They have previously looked at the impact of an ice-free month in the Arctic.
At 1.65 million square miles, or 4.28 million square kilometres, this year's Arctic sea ice minimum – the day with the least frozen seawater – was one of the lowest on record since 1978, but above the all-time low observed in September 2012. That was a stark decline compared to the average coverage of 6.85 million square kilometres between 1979 and 1992. When the Arctic Ocean has less than 1 million square kilometres of ice, scientists say the Arctic is ice-free.
This year is on track to be the hottest on record, according to the World Meteorological Organisation, which has also issued a red alert to highlight that 2015-2024 will be the warmest decade in history.
Prof Jahn and Dr Céline Heuzé from the University of Gothenburg estimated the first ice-free Arctic day using output from over 300 computer simulations. They found that most models predicted that the first ice-free day could happen within nine to 20 years after 2023, regardless of how humans alter their greenhouse gas emissions.
The researchers found that a series of extreme weather events could melt two million square kilometres or more of sea ice in a short period of time: an unusually warm autumn first weakens the sea ice, followed by a warm Arctic winter and spring that prevents sea ice from forming. When the Arctic experiences such extreme warming for three or more years in a row, the first ice-free day could happen in late summer. Warm years have already happened – for example, in March 2022 areas of the Arctic were 10°C (50°F) warmer than average, and areas around the North Pole were nearly melting.
With climate change, the frequency and intensity of these weather events will only increase, according to Dr Heuzé. Sea ice protects the Arctic from warming by reflecting sunlight back into space. With less reflective ice, darker ocean waters will absorb more heat from the Sun, further increasing temperatures in the Arctic and globally. In addition, warming in the Arctic could change wind and ocean current patterns, leading to more extreme weather around the world.
But there is also good news: a drastic cut in emissions could delay an ice-free Arctic and reduce the time the ocean stays ice-free, according to the study. “Any reductions in emissions would help preserve sea ice,” Prof Jahn said.
