As climate scientists release new evidence pointing to the possible “collapse” of the Gulf Stream, experts are warning that its disappearance would usher in a “calamitous climate catastrophe” not just for Canadians living on the east coast, but for hundreds of millions more people worldwide.
The warning comes amid a new study published in the journal Nature Climate Change, which found evidence of the Gulf Stream losing “stability” over the course of the last century. Should the stream continue to lose strength and eventually collapse, the study’s author warned of “severe impacts on the global climate system.”
The stream is essentially part of a larger overall current called the Atlantic Meridional Overturning Circulation (AMOC), a huge river of warm, salty water that originates from the American tropics in Mexico and flows through the upper layers of the Atlantic, eventually passing Newfoundland and Labrador and into the Nordic seas off the coast of Scandinavia and the U.K.
Some of the warm water would eventually go up into the Arctic, while some would become more dense after losing heat and moisture to the atmosphere, eventually starting to sink and ultimately returning towards the equator to heat up again, much like a “conveyor belt.”
In a press release from the Potsdam Institute for Climate Impact Research in Germany, the study’s lead author, Dr. Niklas Boers, described the current as one of Earth’s “key circulation systems,” but pointed to the stream as currently being at its weakest in the last 1,000 years.
The AMOC has been speculated to undergo two modes: the first of which is described as a strong current that helps the gush of warm water from the tropics maintain large parts of Europe’s current climate, while the second is described as a weak mode, which if activated is considered to be one of the world’s climate tipping points towards catastrophic damage.
Boers’ research pointed to the collapse of the stream from its currently strong mode to the weak mode as due to a number of factors, including the increased flow of fresh water from the melting Greenland ice sheet and sea ice from glaciers in the north, much of which is caused by the effects of global warming.
“I wouldn’t have expected that the excessive amounts of freshwater added in the course of the last century would already produce such a response in the overturning circulation,” Boers said in the press release.
“We urgently need to reconcile our models with the presented observational evidence to assess how far from or how close to its critical threshold the AMOC really is.”
According to University of Toronto professor Kent Moore, the waning strength of the stream could have dire consequences not just for Canada’s coastal communities, but for potentially hundreds millions of people worldwide.
Moore pointed to what he calls the most well-known evidence of a shift from strong to weak mode in the Gulf Stream — an event that occurred near the end of the Earth’s last ice age, around 13,000 years ago.
As large swaths of ice began to melt from the ice sheets in North America, the sudden influx of previously frozen fresh water being dumped into the ocean prevented the heavier saltwater in the stream from sinking and returning to the equator, resulting in a weaker current.
The result, according to Moore, was a cataclysmic event that sent what is considered Europe today into a “deep freeze” for about 1,000 years. As the Gulf Stream “shut down,” so did the flow of warm waters which brought warmth to the Scandinavian seas off the European continent.
Should the same “shut down” happen today, prompted by global warming, Moore said that the resulting consequences would also have a devastating effect on millions around the world — including parts of Canada.
Sea levels around communities in Canada’s Atlantic and the American northeast would rise while rain and weather patterns, which millions of people rely on to help provide crops and food, could shift within mere decades.
“So the impacts to Canada would be extreme,” said Moore. “I’m pretty sure that the Maritimes would become cooler because there’s not that source of warmth offshores, and sea levels would rise.”
According to Moore, however, the real problem arising from the loss of the Gulf Stream would be the rapid decrease in temperatures across Europe — resulting in a massive displacement of 50 million people there who would essentially no longer be able to live and thrive there.
“That’s the real issue — what will we do? How will we support those individuals?” asked Moore.
“Thinking globally, that would be the largest impact, just a total disruption to the whole thing — like almost every aspect of our life.”
As for how to prevent or slow the stream from collapsing, Moore said that it would be very unlikely for humans to find a way to “engineer” their way out of it.
Instead, he pointed to mitigating the effects of global warming as being the only approach.
“Even if we maintain temperatures as they are today, Greenland will still continue to melt because it’s just warm, and so to prevent Greenland from getting warmer, we need to reduce our use of CO2,” he said.
“And that’s really the only way to make sure that this transition doesn’t happen and avert what would really be a calamitous climate catastrophe”