Arctic ice has experienced ‘irreversible’ thinning since 2007, study finds


Arctic sea ice declined dramatically in 2007 and never recovered. New research suggests the loss was a fundamental shift unlikely to be reversed this century, if ever – perhaps evidence of the kind of climate tipping point scientists have warned the planet could pass as let her warm up.

The conclusion comes from three decades of data on the age and thickness of ice escaping from the Arctic every year east of Greenland. Scientists from the Norwegian Polar Institute have found a stark difference in ice levels before and after hitting an all-time low in 2007.

In the years since, the data shows that the Arctic has entered what researchers have called a “new regime” – a regime that results in a trend towards much thinner and younger ice cover than it does. was before 2007, according to the researchers. They link the change to rising ocean temperatures in the rapidly warming Arctic, due to human emissions of greenhouse gases.

“Our analysis demonstrates the lasting impact of climate change on Arctic sea ice,” they wrote in the journal Nature.

Walt Meier, a senior researcher at the National Snow and Ice Data Center at the University of Colorado Boulder, compared the 2007 low to a boxer getting punched. All punches leading up to it weaken the fighter, but this biggest punch is too much for the boxer to overcome.

This does not mean that the Arctic ice is completely eliminated, but that it cannot recover quickly.

“You’re in a new situation, a new balance, where you can’t easily go back to where you were,” said Meier, who was not involved in the new research.

The scientists’ analysis is based on data captured in the Fram Strait, a passage between Greenland and the Norwegian archipelago known as Svalbard through which sea ice regularly flows on its way to the Atlantic. North. Underwater radar systems can detect the volume of ice flowing overhead, while satellites and buoys track ice movement and weather in the Arctic.

They found a dramatic change occurred in 2007, when the Colorado Ice Research Center reported record sea ice cover 38% below normal and 24% below the previous record set. in 2005.

Until 2007, they observed sea ice at a variety of thicknesses and ages, often with bumps and ridges that originated from former pack ice packs. But in recent years, the ice floes have been smoother and have a more uniform thickness, indicating that they are younger and have a shorter lifespan. It’s a concern for a variety of reasons: rising sea levels, loss of habitat for arctic creatures, and lessening of the albedo effect, which is when ice reflects sunlight back into the space. A less icy Arctic absorbs more solar heat.

Overall, sea ice spends 37% less time in the Arctic before escaping through Fram Strait to melt into the Atlantic, about 2.7 years on average since 2007, the researchers found. . The amount of ice thicker than 4 meters (about 13 feet) crossing the strait fell more than 50% from the record low of 2007.

The research bolsters previous studies that show losses of nearly all of the oldest and thickest ice that once covered the Arctic, and that pack ice is circulating around the Arctic and moving through Fram Strait faster as the ice cover is collapsing.

The study articulates scientists’ concerns since the 2007 record (and since broken in 2012). At the time, some wondered if this was the start of an epic meltdown. That didn’t happen, but there was no significant rebound either.

Researchers have been reluctant to be overly declarative about potential changes to the Arctic sea ice system as a whole because there is so much variability in ice cover from year to year, Meier said. The new study could change that, he said.

“They’re making a pretty good case and putting together a lot of data to say, yes, there’s a fundamental change and we’re in this new regime,” Meier said.

Some, however, disagree on one of the researchers’ conclusions.

“I’m not convinced it’s irreversible,” said Harry Stern, a mathematician and sea ice researcher at the University of Washington’s Applied Physics Laboratory. “If you reverse the conditions, you could reverse the changes in ice thickness.”

The study authors said this would take a long time, even under the most optimistic scenarios of global warming and reduced emissions. Even if carbon dioxide emissions fell to zero within the next 50 years, it would take decades more for the ocean to lose all the heat it has accumulated since humans started burning fossil fuels and to emit greenhouse gases.

“Given that the heat content of the ocean in areas of sea ice formation…has increased,” the authors wrote in an email response to questions, “we suggest that the changes are irreversible at least with the current climate”.

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