“The first ice-free day in the Arctic won’t change things dramatically,” said 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.”

For the first time, an international research team, including CU Boulder climatologist Alexandra Jahn and Céline Heuzé from the University of Gothenburg in Sweden, used computer models to predict when the first ice-free day could occur in the northernmost ocean. An ice-free Arctic could significantly impact the ecosystem and Earth’s climate by changing weather patterns.

The findings were published 3 December in the journal Nature Communications, accelerating the rate of decline that previous projections placed on Arctic sea ice change.

Jahn and Heuzé projected/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 earliest ice-free day in the Arctic Ocean could occur within three years. In total, nine simulations suggested that an ice-free day could occur in three to six years.

The researchers found that a series of extreme weather events could melt two million square kilometers or more of sea ice in a short period of time, but a drastic cut in emissions could delay the timeline for an ice-free Arctic and reduce the time the ocean stays ice-free, according to the study.

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