Atlantic Ocean’s slowdown tied to changes in the Southern Hemisphere!

“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.

Looking at other observations to determine the cause, the researchers ruled out what had been the prime suspect until now: that massive melting and freshening in the North Atlantic could stop water from sinking and put the brakes on the overturning circulation, which moves warmer water north along the ocean’s surface and sends cold water southward at depths.

“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.”