by the sea ice Arctic it dropped dramatically in 2007 and has never recovered. A paper published in Nature this week suggests the loss was a fundamental change and is unlikely to be reversed this century, if ever – thus evidence of one of the points of no return that scientists have warned the planet could face. to pass as it warms.
The conclusion comes from three decades of data on the age and thickness of the ice that leaves the Arctic annually as it flows into the North Atlantic east of Greenland. Scientists at the Norwegian Polar Institute discovered a remarkable difference in ice levels before and after it reached an all-time low in 2007.
In the years since, the data show that the Arctic has entered what researchers have called a “new regime” — one that brings with it a trend toward much thinner and younger ice cover than before 2007, the researchers say. researchers . Scientists link this change to rising ocean temperatures in the rapidly warming Arctic, due to greenhouse gas emissions. the greenhouse effect.
“Our analysis demonstrates its lasting impact climate change in Arctic sea ice,” write the authors of the article published this week in the journal Nature.
THE throw unconscious
Walt Meier, a scientist at the National Snow and Ice Data Center at the University of Colorado at Boulder, compared the 2007 low to a boxer taking a knockout punch. Every punch he takes weakens the boxer, but this biggest blow is too much for him to overcome.
This does not mean that the Arctic ice will be completely eliminated, but it does mean that it will not be able to recover quickly. “You’re in a new state, a new equilibrium, and you won’t be able to easily go back to where you were,” said Meier, who was not involved in the research now published in nature.
Data on this year’s potential maximum Arctic sea ice, released by the U.S. Ice Data Center on Wednesday, confirm what recent trends have been saying: The 5.64 million square miles of ice cover seen on March 6 was the fifth smallest of all records. This height generally coincides with the mean annual Arctic sea ice maximum.
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Follow the Ice Journey
The new analysis by scientists at the Norwegian institute is based on data collected from the Fram Strait, a passage between Greenland and the Norwegian archipelago known as Svalbard, through which Arctic sea ice regularly flows on its way to the North Atlantic. Underwater radar systems can detect the volume of ice flowing overhead, while satellites and buoys track the ice’s movement and the time it spends in the Arctic before escaping from the pole.
Researchers discovered a dramatic change in 2007, when the Colorado Ice Research Center reported record sea ice coverage, 38 percent less than normal and 24 percent less than the previous record, set in 2005.
By 2007, they observed sea ice of varying thickness and age, often with collisions of older ice pieces joining together. But in more recent years, the ice sheets have been softer and more uniformly thick, indicating they are younger and shorter-lived.
This is worrisome for several reasons: It could mean a loss of habitat for animals living in the Arctic and a reduction in the albedo effect, when ice reflects sunlight back into space. An Arctic with less ice absorbs more of the sun’s heat.
Globally, ice sheets are spending 37 percent less time in the Arctic before escaping through the Fram Strait to melt in the Atlantic, or about 2.7 years on average since 2007, the paper’s authors found. The amount of ice over 4 meters thick passing through the strait has fallen by more than 50 percent since the record low of 2007.
New cycle?
The research builds on previous studies showing losses of almost all of the older, thicker ice that once covered the Arctic, and confirms that ice sheets are flowing around the Arctic and through the Fram Strait faster as the ice sheet thins.
The study responds to concerns raised by scientists since the record low set in 2007 (and since broken in 2012). At the time, some wondered if this was the beginning of an epic collapse. It didn’t, but there wasn’t a significant resurgence either.
Researchers have been reluctant to be too bullish about possible changes in the Arctic 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, says Walt Meier. “In this paper they make a good case and put together a lot of data to say, yes, there is a fundamental change and we are in this new regime,” Meier said.
Some disagree, however, with 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 can reverse the changes in ice thickness.”
The study authors say, however, that this will take a long time even under the most optimistic scenarios. global warming and reducing emissions. Although carbon dioxide emissions carbon To drop to zero sometime in the next 50 years, it will take several decades for the ocean to lose all the heat it has accumulated since humans started burning. fossil fuels and issue greenhouse gases.
“Ocean heat content in regions of sea ice formation has increased,” the authors wrote in an emailed response to questions from The Washington Postconcluding, therefore, that: “we suggest that the changes are irreversible, at least with climate drift”.
