Global Courant
New research has pushed back the time when the Arctic Ocean is predicted to be free of summer ice.
An article published Tuesday in the journal Nature concludes that those northern waters could be open for months as early as 2030, even if humanity manages to drastically cut its greenhouse gas emissions.
“It brings it about a decade earlier,” said Nathan Gillett, a Canadian environmental and climate change scientist and one of the study’s co-authors.
Gillett and his colleagues had noticed the growing discrepancies between what climate models say should be happening to sea ice and what is actually happening.
“On average, the models underestimate sea ice reduction compared to observations,” Gillett said.
Greenhouse gas effects ‘scale up’
The researchers wanted to know how much they would need to adjust the model to make it fit the data — and what those adjustments might reveal if projected into the future.
To do this, the scientists first teased out the effect of greenhouse gases from other factors that influence sea ice loss, such as man-made chemicals from aerosols or natural events such as volcanic eruptions. The impact of aerosols was found to be negligible, and the study concluded that natural events contributed no more than 10 percent to sea ice loss.
With isolated greenhouse gases as the main culprit, they then looked at how those emissions were used in their climate model. By “scaling up” the effect of greenhouse gases, the researchers achieved a much closer fit with satellite images of ice cover.
A small cruise ship sign outside Cambridge Bay, Nunavut, on the western edge of the Northwest Passage, in the summer of 2022. (Matisse Harvey/Radio-Canada)
This more accurate assessment of the influence of greenhouses turned out to be accompanied by a warning.
Previous estimates had suggested Arctic summer sea ice would disappear as early as the 2040s at the earliest. If humanity succeeds in reducing its emissions, even sea ice could survive year-round.
But once the model was aligned with what was happening on the water, predictions about the disappearance of summer ice came a lot closer.
“The range then is 2030 to 2050,” Gillett said. “And even under the lowest emissions scenario, with the scaling up, the Arctic is ice-free.”
Summer ice will ‘very likely’ disappear
Nothing is certain, Gillett warns. But this is close.
“I would say it’s very likely.”
That would mean the Arctic would have less than a million square miles of sea ice by the end of the melting season in September, even with low emissions. If emissions remain high, that ice-free period could last for months.
The average ice size for April 2023 was 14 million square kilometers.
Also, the study is the first to measure sea ice trends for each month of the year. Previous studies focused on the summer months.
Comparing ice extent from year to year — February 2019 to February 2018, for example — the data showed ice loss from climate change in every month of the year.
‘More sensitive than we thought’
Pam Pearson of the International Cryosphere Climate Initiative, a network of policy experts and researchers, has seen the Nature study and said it is strong evidence that greenhouse gases are changing the Arctic faster than previously thought.
“More ice is being lost, faster than even the most recent models predict,” she wrote in an email.
“Today’s observations even exceed high-end predictions. Global ice supplies are simply more sensitive than we thought to small changes in warming.”
Gillett said an ice-free Arctic would certainly accelerate the warming of the countries surrounding the waters – already warming three times the global average. The fragile ecosystem that relies on sea ice — home to everything from algae to polar bears — would change dramatically.
And in terms of climate, what happens in the Arctic may not stay in the Arctic.
“People have been looking at the potential implications of Arctic warming for climate at lower latitudes,” Gillett said. “That’s still a matter of debate.”
