New study predicts Arctic Ocean will be 'ice free' in summer by middle of this century - Whitecourt Star

The forecast may not alter even if the world cuts current CO2 emissions as best it can

The new study on Artic Ocean ice predicts that a stunning change will have happened even before the middle of the current century. Dirk Notz

A startling new analysis of climate models, made by scientists at Montreal’s McGill University and elsewhere, has made a grim prediction — within decades, the Arctic Ocean will hold practically no summer ice at all.

Science Alert reports that the new study predicts the stunning change will have happened even before the middle of the current century, and the forecast may not alter even if the world cuts current CO2 emissions as best it can.

The study was published in the journal Geophysical Research Letters. In it, scientists looked at 40 different climate models that mimic how sea ice patterns will evolve in the Arctic in the coming decades. The researchers used various mocked-up situations, including some where emissions continued as they are (offering little or no protection to the climate) and some where the emissions were sharply reduced.

The state-of-the-art models used were from the World Climate Research Program’s Coupled Model Intercomparison Project, known as CMIP6.

In the majority of simulations, the Arctic Ocean loses practically all of its summertime ice, whatever the measures taken, by 2050. The paper predicts:

“The CMIP6 models simulate a large spread for when Arctic sea-ice area is predicted to drop below 1 million km2, such that the Arctic Ocean becomes practically sea-ice free.

“However, the clear majority of all models, and of those models that best capture the observed evolution, project that the Arctic will become practically sea-ice free in September before the year 2050 at future anthropogenic CO2 emissions of less than 1,000 [gigatonnes of] CO2 above that of 2019 in all scenarios.”

Scientists have sounded the alarm on a devastating depletion of ice in the Arctic for decades. But the speed of the deterioration under the new models has been an eye-opener.

Dirk Notz, a polar geophysicist from the University of Hamburg in Germany, told Science Alert:

“If we reduce global emissions rapidly and substantially, and thus keep global warming below 2 °C relative to pre-industrial levels, Arctic sea ice will nevertheless likely disappear occasionally in summer even before 2050. This really surprised us.”

In a release on the study, the McGill University team pointed out that although the ice did deplete under low emissions scenarios, “How often the Arctic will lose its sea-ice cover in the future critically depends on future CO2 emissions, the study shows.”

Ice was expected, under high-emissions modelling, to vanish rapidly. But that was not expected to always be the case under low-emissions scenarios. And humans must play their part.

“If emissions are reduced rapidly, ice-free years only occur occasionally,” the McGill release reads. “With higher emissions, the Arctic Ocean will become ice-free in most years. This tells us that humans still determine how often the Arctic Ocean will be ice-free in the summer, depending on our future level of emissions.”

“While the Arctic sea-ice extent is decreasing during this transition to an ice-free Arctic, the year-to-year variability in extent greatly increases, making life more difficult for local populations and ice-dependent species,” says Bruno Tremblay, associate professor in the Department of Atmospheric and Oceanic Sciences at McGill.

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2020-04-23 14:11:44Z
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