Is the Gulf stream nearing collapse? New climate study suggests it's possible.
It's definitely slowing down and becoming more unstable. The impact on global weather patterns could be enormous.
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The Atlantic Meridional Overturning Circulation (AMOC), of which the Gulf stream system is a major part, may be in danger of collapse, according to new research by Niklas Boers, Department of Mathematics and Computer Science, Freie Universität Berlin, just published in Nature Climate Change. Because the AMOC redistributes heat the consequences of such a failure would be severe for the world’s weather,. Writes the University of Copenhagen:
The finding is worrying as well as a surprise. The AMOC, to which also the Gulf stream belongs, is responsible for the relatively mild temperatures in Europe and influences weather systems worldwide. A collapse of this ocean current system, which has so far not been considered likely under the current levels of global warming will therefore have severe consequences on global and especially European weather and climate.
Boers study is part of the European TiPES project, coordinated by the University of Copenhagen, Denmark and the Potsdam Institute for Climate Impact Research, Germany. It expands on previous research, including a February 2021 study from the PIK titled Gulf Stream System at its weakest in over a millennium (Link below). Stefan Rahmstorf explains the AMOC like this:
“AMOC is a large system of ocean currents that carry warm water from the tropics northwards into the North Atlantic. The Gulf Stream System works like a giant conveyor belt, carrying warm surface water from the equator up north, and sending cold, low-salinity deep water back down south. It moves nearly 20 million cubic meters of water per second, almost a hundred times the Amazon flow."
Previous model simulations and data from paleoclimate proxy records suggest that the AMOC can be in two distinct modes: A strong mode, which it is in currently or a substantially weaker mode of operation. This implies that abrupt transitions between the two circulation modes can happen. Such a sudden transition would be disastrous. From the Copenhagen statement:
A collapse from the currently attained strong circulation mode would therefore—among other impacts—cool Europe substantially as well as strongly impact the tropical monsoon systems.
Scientists have been studying the AMOC directly only since 2004 but the circulation process leaves so-called fingerprints in sea-surface temperature and salinity patterns in the Atlantic ocean. Boers’ detailed analysis of these fingerprints suggests that the AMOC weakening during the last century is indeed likely to be associated with a loss of stability, and thus with the approaching of a critical threshold beyond which this major global water circulation system could collapse.
While prior papers found consistent evidence that the AMOC slowdown in the 20th century is unprecedented in the past millennium and is likely linked to human-caused climate change, Boers’ paper introduces what he calls “a robust and general early-warning indicator for forthcoming critical transitions.” From Boers’ paper:
Significant early-warning signals are found in eight independent AMOC indices, based on observational sea-surface temperature and salinity data from across the Atlantic Ocean basin. These results reveal spatially consistent empirical evidence that, in the course of the last century, the AMOC may have evolved from relatively stable conditions to a point close to a critical transition.
Boers seems a bit puzzled by the findings himself. In the University of Copenhagen statement, he says:
"Most evidence suggests that the recent AMOC weakening is caused directly by the warming of the northern Atlantic ocean. But according to our understanding, this would be unlikely to lead to an abrupt state transition. Stability loss that could result in such a transition would be expected following the inflow of substantial amounts of freshwater into the North Atlantic in response to melting of the Greenland ice sheet, melting Arctic sea ice and an overall enhanced precipitation and river runoff."
The statement adds:
However, although a first sign of regional destabilization of the Greenland Icesheet has been detected, recent Greenland runoff should not be sufficient for destabilizing the AMOC.
So there you have it—not exactly a prediction nor a date but yet another troubling sign that the destruction of our atmosphere by the carbon that is warming the planet may well be more rapid and deadly than we have previously thought. The final answer to this one will be among the biggest climate tipping points of all.
Dig Deeper
Observation-based early-warning signals for a collapse of the Atlantic Meridional Overturning Circulation (Niklas Boers)
Ocean current system seems to be approaching a tipping point (University of Copenhagen)
Gulf Stream System at its weakest in over a millennium (Science News)
What is the Atlantic Meridional Overturning Circulation?
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