The Peterborough Examiner e-edition

Research advances date for likely summer ice-free Arctic by decade

Northern waters could be open for months by 2030

BOB WEBER

New research has moved up the time by which the Arctic Ocean is predicted to be free of summer ice.

A paper published Tuesday in the journal Nature has concluded those northern waters could be open for months at a time as early as 2030, even if humanity manages to drastically scale back its greenhouse gas emissions.

“It brings it about a decade sooner,” said Nathan Gillett, an Environment and Climate Change Canada scientist and one of the co-authors of the study.

Gillett and his colleagues had noticed the growing differences between what climate models say should be happening to sea ice and what’s actually going on.

“The models, on average, underestimate sea ice decline compared with observations,” Gillett said.

They wanted to know how much they’d have to tweak the model to make it fit the data — and what those tweaks might reveal if they were projected into the future.

To do so, the scientists first teased out the effect of greenhouse gases from other factors that affect sea ice loss, such as artificial 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 per cent of sea ice loss.

With greenhouse gases isolated 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 better fit with satellite images of ice cover.

That more accurate assessment of the influence of greenhouses turned out to come with a warning.

Previous estimates had suggested Arctic summer sea ice wouldn’t disappear until the 2040s at the earliest. If humanity managed to bring its emissions down, year-round sea ice might even survive.

But, once the model had been brought in line with what was happening on the water, predictions of summer ice disappearance got a lot closer. “The range is then 2030 to 2050,” Gillett said. “And even under the lowest emission scenario, with the scaling the Arctic is ice-free.”

Nothing is certain, Gillett cautions. But this is close. “I would say it’s extremely likely.”

That would mean that, by the end of the melt season in September, the Arctic would have less than one million square kilometres of sea ice, even under low emissions. If emissions remain high, that ice-free period could last months. The average ice extent for April 2023 was 14 million square kilometres.

As well, the study is the first to measure sea ice trends for every month of the year. Previous studies have focused on the summer months.

By comparing ice extent yearover-year — February 2019 against February 2018, for example — the data showed ice loss from climate change in every month of the year.

Gillett said an ice-free Arctic would certainly hasten the warming of lands around the waters — already warming at three times the global average. The fragile ecosystem that depends on sea ice — home to everything from algae to polar bears — would change utterly.

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2023-06-07T07:00:00.0000000Z

2023-06-07T07:00:00.0000000Z

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