Why the melting of Arctic ice has temporarily reversed global warming

The book, published in Nature Geoscience was directed by Lloyd Keigwin of the Woods Hole Oceanographic Institution with researchers from this institution as well as Scripps and Oregon State University.

The researchers behind this study, working aboard US Coast Guard Cutter Healy, badyzed deep oceanic mud sediments, which contain shells of dead marine organisms long known as foraminifera. In these shells, scientists have detected a long – sought anomaly recorded in the language of oxygen atoms.

The shells contained a disproportionate volume of oxygen 16, a lighter form (or isotope) of the element that is found in high levels in glaciers. This is because the oxygen 16, containing two fewer neutrons and therefore lighter than the oxygen 18, evaporates more easily from the ocean but does not fall off as easily . As a result, it often falls as snow at high latitudes and is stored in large expanses of ice.

"It's the smoking gun for detecting glacial lake explosions," Driscoll said. And that means that the results can also be the trigger for younger Younger Dryas.

It is thought that at the end of the ice age and when the huge layer of Laurentide ice began to recede in North America, the meltwaters fed large lakes. at the top of the depressed surface of the continent. This included the gigantic glacial lake Agbadiz, which extended from the Great Lakes to the northwest of most of Canada.

Previous research had shown that for a long time, much of the freshwater drained the Mississippi River and the Gulf of Mexico. . But at one point, as the ice sheet continued to shrink, the stream of water appeared to have been suddenly redirected north or east, where it could cause further damage to the ocean circulation in the north. l & # 39; Atlantic.

There has long been a scientific debate on where all the meltwater actually entered the ocean, some claiming that this would have occurred in the St. Lawrence River, which is now Between Montreal and Quebec City and opens in the Atlantic

. Research indicates that flood waters flowed from the Mackenzie River, which flows through the Northwest Territories and flows directly into the Arctic Ocean.

This would certainly have been a huge flow of fresh water. "I would say somewhere between the Mississippi and the Amazon," said Keigwin,

which could have interfered with Atlantic traffic, which is crucial as it carries warm water north and warms thus the high latitudes. Eventually, the waters of the traffic become very cold when they travel north, but because they are also very salty, they sink due to their high density and return to the south.

Achilles talcum of circulation. And the new study argues that, although glacial water would have entered the seas very far near the current Alaska-Canada border, it would have then circulated around the Arctic, traveling south after Greenland and penetrating key regions However, not everyone is convinced, including some researchers who have already published results suggesting that the flood or the flow was rather at the same time. 39, is across the St. Lawrence River.

"They have produced a good signal of freshwater release in the Arctic Ocean, but the findings are based on an uncertain timeline that, in trying to link events so closely, requires confirmation Independent ", Peter Clark, a geoscientist from Oregon State University who has published evidence to support the theory of the St. Lawrence River, said in an email.

Anders Carlson, co-author of Clark A colleague from Oregon State University sent out a geological survey stating that, as he said in an email, "the waters of Lake Agbadiz were clearly directed to the east. at the beginning of the Younger Dryas. "

" This does not prevent Younger Dryas "Carlson wrote," but the floods are of local origin and are not related to the drainage of Lake Agbadiz. "

the gigantic lake freshwater and other melting events to the Atlantic interfered with the circulation of the ocean – they simply disagree about how it is arrived there.

The question becomes whether it is possible to interfere even more dramatically with traffic "I do not think there are lakes on earth that are big enough to do that", said Keigwin. "It must come from the ice, because it's the largest reservoir of freshwater, and Greenland is the mbad of ice you'd be most suspicious of, because it's there, ready to do enough damage. "

no Lake Agbadiz. "Greenland does not have great lakes for storing water," Driscoll said. On the contrary, it releases stable currents of water in the form of glacial runoff that often goes directly into the ocean and releases huge icebergs that slowly melt.

Nobody therefore necessarily expects a sudden flood when Greenland melts. Nevertheless, Driscoll and Keigwin both believe that regular Greenland losses over time, especially if they accelerate, can accumulate.

Climatologists will be eager to point out that, even if the Atlantic traffic shows or stops, carrying as much heat and leading to some cooling of the northern hemisphere, the overall trend of the Global warming will be continuous and could carry it.

We will not repeat Younger Dryas directly, but we can learn from them.

The Washington Post