Greenland melt hasn’t slowed Atlantic current

Last year, a scientific study suggested a scenario that has long worried scientists was coming to pass: a slowdown in the North Atlantic ocean currents that usually redistribute warm and cold waters.

The circulation, called the Atlantic meridional overturning circulation or AMOC, transports enormous amounts of warmth northward from lower latitudes. If it slows down, there will be less heat transport to Europe and higher latitudes, as well as key consequences for warming and sea level rise along the U.S. East Coast.

And now, in the journal Nature Geoscience, a paper has emerged suggesting that while Greenland has already contributed enough water to begin to freshen seas, there hasn’t been enough freshwater yet to slow the AMOC.

The researchers, led by Claus Böning of the Helmholtz Centre for Ocean Research in Germany, used an estimate of 3,200 billion tons of freshwater that has poured out of Greenland between 1995 and 2010, and a prediction that due to increasing melt, that will total 7,500 billion tons by 2020. Their study then uses a model to determine where that freshwater will go.

They found the overturning circulation occurs more in the center of the Labrador Sea. “There’s an instability region in a very limited area off southwest Greenland, where eddies transport the water from the shelf into the interior Labrador Sea,” Böning said.

It was by including these eddies that the model found that most Greenland meltwater exits and flows farther southward.

While the remaining freshwater is probably having an effect, it’s not big enough yet to cause major changes.