CLIMATEWIRE | By the end of the decade, the Arctic Ocean could see its first ice-free day on record — even with modest levels of global warming.
It’s an unlikely scenario, but it’s possible. And it’s growing more plausible as humans continue pouring greenhouse gases into the atmosphere.
Scientists raised the alarm in a study published Tuesday in the scientific journal Nature Communications.
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The research — which relies on climate models simulating trends in global temperatures and Arctic sea ice concentrations — warns the only way to avoid an ice-free day within the next few years is to cut emissions fast enough to stay consistent with the Paris Agreement’s most ambitious goal, capping global warming at 1.5 degrees Celsius.
Yet experts agree the world is all but certain to blow past that target, with current global climate pledges putting the planet on track for more than 2.6 C of warming by the end of the century.
That means the Arctic’s first ice-free day is likely to occur within two decades, the new study finds. But if the right conditions line up, it could happen within three to six years.
“It’s definitely a very unlikely event,” said Alexandra Jahn, a climate scientist at the University of Colorado, Boulder, who co-authored the study with University of Gothenburg scientist Céline Heuzé. “We’re looking at the outer edge of what could happen.”
The worst-case scenario would require a perfect storm of weather and climate conditions over the next few years, Jahn said.
Temperatures would need to be unusually warm, especially in the fall, winter and spring. That’s more likely to happen when high-pressure weather systems move over the Arctic, trapping warm air in place. Stormy weather also could help prime the ocean for rapid melting — breaking up the sea ice and helping it dissolve faster into the ocean.
If all of these conditions occurred together — and persisted for a few years — the Arctic Ocean could experience a catastrophic ice loss event by 2027.
Whether it happens that quickly is largely up to chance. But that day is on the horizon, barring a dramatic shift in humanity's response to global warming.
Climate change has caused sea ice to dwindle for decades, and without it an ice-free Arctic Ocean would be impossible under any circumstances, Jahn said.
But the exact year it occurs will depend on natural fluctuations in the weather, giving scientists an uncertainty range spanning several decades.
The study is careful to focus on just the first ice-free day — by scientific definitions, that’s the first time Arctic sea ice cover shrinks below 1 million square kilometers, or 386,102 square miles, on the surface of the ocean. That makes it different from other recent studies, which have investigated the timelines for the Arctic’s first ice-free month or ice-free summer.
If the first ice-free day does occur within the next few years, it will probably be followed by several more. In these model simulations, the ice-free period lasts 11 to 53 days. That means it could end in less than two weeks, or it could drag on into the first ice-free month — another climate milestone.
Jahn cautions that these are improbable scenarios, with less than a 5 percent chance of occurring under current circumstances. But the likeliest model scenarios still suggest that the first ice-free day will occur by midcentury or potentially sooner. Studies predicting the first full ice-free month have suggested similar timelines if the world blows past the 1.5 C threshold.
That doesn’t mean climate action doesn’t matter for the Arctic, Jahn cautioned — just the opposite. Reducing greenhouse gas emissions as much as possible will limit the total amount of sea ice that melts away, making ice-free summer events less frequent and protecting sea ice cover in the colder parts of the year.
“Even if we miss the target, we can stick to 1.6 degrees,” Jahn said. “Then that will be a great achievement and will definitely have a big impact on how the Arctic will look like in the second part of the 21st century.”
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2024. E&E News provides essential news for energy and environment professionals.