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posted by martyb on Wednesday October 05 2016, @05:45PM   Printer-friendly

Phys.Org is reporting on the results of a recent study by University of Washington oceanographers. The paper, published 28 July, 2016 in Geophysical Research Letters [abstract only, full text paywalled] details research pointing to a cause of the slowdown in the Atlantic Ocean circulation currents.

From the Phys.org article:

The ocean circulation that is responsible for England's mild climate appears to be slowing down. The shift is not sudden or dramatic, as in the 2004 sci-fi movie "The Day After Tomorrow," but it is a real effect that has consequences for the climates of eastern North America and Western Europe.

Also unlike in that movie, and in theories of long-term climate change, these recent trends are not connected with the melting of the Arctic sea ice and buildup of freshwater near the North Pole. Instead, they seem to be connected to shifts at the southern end of the planet, according to a recent University of Washington study in the journal Geophysical Research Letters.

"It doesn't work like in the movie, of course," said Kathryn Kelly, an oceanographer at the UW's Applied Physics Laboratory. "The slowdown is actually happening very gradually, but it seems to be happening like predicted: It does seem to be spinning down."

The study looked at data from satellites and ocean sensors off Miami that have tracked what's known as the Atlantic overturning circulation for more than a decade. Together they show a definite slowdown since 2004, confirming a trend suspected before then from spottier data.

[...] "It appears that this 10-year slowdown is not related to salinity," Kelly said. In fact, despite more ice melt, surface water in the Arctic is getting saltier and therefore denser, she said, because of less precipitation. "That means the slowdown could not possibly be due to salinity—it's just backwards. The North Atlantic has actually been getting saltier."

[More...]

Instead, the authors saw a surprising connection with a current around the southern tip of South Africa. In what's known as the Agulhas Current, warm Indian Ocean water flows south along the African coast and around the continent's tip toward the Atlantic, but then makes a sharp turn back to join the stormy southern circumpolar current. Warm water that escapes into the Atlantic around the cape of South Africa is known as the Agulhas Leakage. The new research shows the amount of leakage changes with the quantity of heat transported northward by the overturning circulation.

"We've found that the two are connected, but I don't think we've found that one causes the other," Kelly said. "It's more likely that whatever changed the Agulhas changed the whole system."

She believes atmospheric changes may be affecting both currents simultaneously.

"Most people have thought this current should be driven by a salinity change, but maybe it's the [Southern Ocean] winds," Kelly said.

The finding could have implications for northern European and eastern U.S. climates, and for understanding how the world's oceans carry heat from the tropics toward the poles.

Have any Soylentils noticed any effect from the current slowdown?


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  • (Score: 1) by khallow on Thursday October 06 2016, @03:15AM

    by khallow (3766) Subscriber Badge on Thursday October 06 2016, @03:15AM (#410942) Journal

    Hoover Dam is right next to Las Vegas too, and Lake Mead is YUGE. These days the water levels are low though, and we might see climate change kill Las Vegas.

    Resource mismanagement is not climate change. There's a two thousand year reconstruction [noaa.gov] of rainfall in the Colorado river watershed which shows several droughts more severe than the present. From the link:

    Droughts in the West, including in the Upper Colorado Basin, have been getting more widespread and severe during the last 50 to 90 years of instrument-based weather records (large-scale U.S. weather records go back to 1895). Tree ring records provide a useful paleoclimatic index that extends our historical perspective of droughts centuries beyond the approximately 100-year instrumental record. A 2129-year paleoclimatic reconstruction of precipitation for northwest New Mexico indicates that, during the last 2000 years, there have been many droughts more severe and longer-lasting than the droughts of the last 110 years. This has implications for water management in the West. For example, the Colorado Compact is the legal agreement used for allocation of Colorado River waters among the western states. The Compact was negotiated early in the 20th century during a very wet period, which was not representative of the long-term climatic conditions of the West.