Tuesday , October 26 2021

We might be wrong about ocean circulation and it will have a big impact



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It can be the biggest wild card in the climate system. Scientists have long been afraid that the so-called "rollover" in the Atlantic could slow down or even stop because of climate change – which would have enormous consequences for the planet.

But at the same time, researchers have a limited understanding of how circulation actually works, because measuring it in its huge and distant currents is extremely difficult. And now, an important new research that aims to do just that is a dramatic review of our understanding of our own circulation.

A new series of 21-month observations on the ice waters of Greenland have revealed that most of the rollover – which not only wastes water but also returns to the south of the ocean – takes place to the east rather than the west from the vast ice island.

If this is correct, the climate models that indicate that circulation will slow down, because climate change may need to be reviewed to take this into account.

The magnitude of the scientific surprise on a scale of 1 to 10 is quite high, said Susan Lozier, an oceanographer at Duke University, who led a study published on Thursday in science.

"I personally, maybe 7 years old," she said. "But I think it could be more than 9 for the community."

The new results come from $ 32 million in OSNAP or from the rollover of the North Atlantic Subpolar program, the first attempt to comprehensively measure turnover in the remote regions concerned. It is believed that these icy seas are cold, salty waters – very dense – under the sea surface at a depth and then back to the south to the southern hemisphere.

This "rollover" process is decisive, as north-north dumping in the North effectively leads to warmer, more saline water in the north, using a current system that includes Gulf Stream. This heat supply, in turn, creates a climate throughout the region and especially in Europe.

A better understanding of how circulatory works work, as some scientists have already suggested that it is slowing down and has great consequences, including ocean warming and rising sea levels from the eastern coast of the United States.

Global temperature maps in recent years have shown a strange cold temperature in the ocean to the southeast of Greenland, as well as very warm temperatures off the coast of New England.

The cold region, known as the "cold" and "warming hole", is surprisingly abnormal at a time when the Earth and its oceans are otherwise warming up. It is suggested that this means that the amount of heat transported to the north is reduced.

Warm waters near New England, in this interpretation, would have a significant effect – the extra ocean heat that hangs in several southern waters, not a trip to the north.

In this debate, the OSNAP project, whose leaders say they are not using the climate issue, is going to measure their own movements.

The OSNAP array is a kind of scientific line that moves across the North Atlantic from Canada to Scotland, touching the southern end of Greenland. In these waters, researchers have deployed 53 ocean mooring sites, each with several tools.

Vessels have different measurements – ocean temperature, salinity and other readings – at different depths across the Atlantic. And this is how they can get the pulse to say about rollover.

A similar transatlantic measurement system already exists far south to Florida, but scientists believe it is important to measure circulation in less hospitable northern waters, where there is actually sinking, to understand how it works.

And that is where things become interesting. Turning around the massive flow of about 15 million cubic meters of water per second could occur on both sides of Greenland.

To the west is the Labrador Sea, between Canada and Greenland, where great attention has been paid. Particularly afraid that the vast amount of lime waters coming from the west of Greenland, home to some of the largest and most active glaciers, could cause considerable damage here by refreshing the waters and preventing sinking.

In the meantime, east of Irmingers, Greenland and the Norwegian Sea. And the new study reveals that, contrary to many earlier discoveries, most of the water overflows occur in the East rather than in the West.

OceanCirculationCurrents Web(Penny Holliday National Oceanographic Center, Southampton UK)

"I think one of our researches is one of the biggest reports received at home, that the above mentioned documents, which have been discussed, are almost like the wrong cutting of the tree," said Bob Pickart, oceanographer at Woods Hole Oceanographic Authority and one. from the authors of the study.

Duke Lozier said he did not want to criticize older modeling studies – they have been constantly improving, and the new work is on the increase. However, she noted that OSNAP's empirical results differ from some models.

"Some of these models, based on observations, produce five times the amount of Labrador sea water they should be prepared for," said Lozer.

This is important because they are the same models that predict that the climate will heat up and the sea around Greenland will refresh due to melting or more precipitation of the Arctic ice, the loss of salinity may hamper the sinking process and slow down circulation.

But there is still much to learn. The new study is the first major report on OSNAP results, and is only 21 months of mooring data. It is too little time to reveal the change in circulation.

Stephen Rahmstorf, a climate researcher at the Potsdam Institute for Climate Impact Research in Germany, who has suggested that a recession has already started, partly based on the visible cooling and warming model – said the new observations are valuable. However, much more time will be needed to draw the main conclusions.

"It is still a very short time series, more like a snapshot, and I wouldn't want to draw any conclusions about the climatic timeline that I have been most interested in," he said in an e-mail.

The main question now is that if the water sinking actually happens in the east of Greenland, what does it say about the vulnerability of circulation? The answer may be where the rising cold and fresh water from Greenland, which enters the ocean in all directions, eventually ends when it goes into deeper waters.

It is also a little understandable.

Marco Tedesco, who is studying Greenland's Columbus University Earth Observation Center at Lamont-Doherty, said that the new research will increase the focus on the melting of the east coast of Greenland, which is closer to the point of rollover.

"East Greenland is likely to be the next culprit, hiding in the apparent vision, but it was overshadowed by the strong personality of the West Bank," said Tedesco.

2019 © The Washington Post

This article was originally published The Washington Post.

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