Global Warming Has Made Gulf Stream Slowest in 1,600 Years, and That Could Impact Our Weather

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By: Sean Breslin
Published: April 12, 2018

For years, scientists have studied a spot in the North Atlantic Ocean that has bucked the trend of a warming world. Now, they know what impact this colder-than-average region is having on the Gulf Stream.

According to a study published Wednesday in the journal Nature, the Gulf Stream is flowing at its slowest rate in at least 1,600 years, and climate change is the likely culprit. If this slowing trend continues, the researchers fear a shutdown of the Gulf Stream's circulation is possible in the long-term, and that would have disastrous consequences, bringing rapid sea level rise to the East Coast, more extreme winters to Europe and numerous other side effects.

"We know somewhere out there is a tipping point where this current system is likely to break down," study co-author Stefan Rahmstorf, a climate scientist at Germany's Potsdam Institute for Climate Impact Research, told the Associated Press. "We still don’t know how far away or close to this tipping point we might be. ... This is uncharted territory."

(MORE: Four Hurricane Names Retired by WMO)

The slowdown is occurring with the Atlantic meridional overturning circulation (AMOC) in which warm, salty water flows northward, from the tropics toward the North Pole. From there, the water is cooled, sinks below warmer water and is carried southward along the Gulf Stream. But the slowdown means less water is turned over amid the Gulf Stream.

The AMOC has slowed 15 percent since the mid-20th century, the study also concluded.

Global warming is to blame for this slowdown in several ways, according to the study. One is that, despite being colder than the surrounding water, the ocean is simply warmer, and the cold water that's supposed to sink under the warm water just isn't as cold anymore. Also, melting sea ice is adding more fresh water to the mix, which makes it less dense and therefore less likely to sink.

"It’s a slow change at the moment, but we’re changing it," Levke Caesar, a physicist at Potsdam Institute and a co-author of the study, told the AP. "One danger is in the unknown of what will happen. We should expect changes."

The study was performed by Caesar, Rahmstorf and researchers from institutions in Germany, Greece, Spain and NOAA. The size of the cold zone studied measures about 2 million square miles, or about the size of India and Mexico combined, the AP also noted.

Some scientists who weren't involved in the study agreed with the findings, but others said a lack of data left them skeptical of the study. MIT professor Carl Wunsch said the study's "assertions of weakening are conceivable, but unsupported by any data" in an interview with the AP.

A separate study, also released Wednesday in the journal Nature, claims the 150-year slowdown of the AMOC is a result of natural changes, not man-made climate change. But both conclude the slowdown is occurring, and it could impact our weather in the coming years.

"If we do not rapidly stop global warming, we must expect a further long-term slowdown of the Atlantic overturning," Alexander Robinson, a co-author of the second study, told the Guardian. "We are only beginning to understand the consequences of this unprecedented process – but they might be disruptive.”

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