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Gulf Stream – Atlantic Meridional Circulation
A collapse of the AMOC could trigger sharp cooling in parts of Europe, even if the rest of the world continues to warm. Some models indicate that there could be episodes of extreme cold in winter, with cities like London occasionally approaching -20 °C.
For years, scientists have warned about the slowdown in the Atlantic Ocean circulation system, which plays a fundamental role in regulating temperatures in the Northern Hemisphere.
A new modeling study adds an unsettling detail: whether the Atlantic Meridional Overturning Circulation (AMOC) weakens, the path of the Gulf Stream should gradually move north along the east coast of the United States.
Satellite observations suggest this could already happening. The same model also shows that a sudden, sharp jump in the path of the Gulf Stream could act as an early warning sign of a much more serious rupture.
The research, recently in the journal Nature Communications Earth & Environment, was led by René van Westen e Henk Dijkstrafrom the University of Utrecht, in the Netherlands.
The team sought to establish a connection between something difficult to measure directly — the intensity of the AMOC — and something we can track more easily: the Gulf Stream route.
AMOC is, in essence, a gigantic conveyor belt. At the surface, warm, salty water moves north from the tropics toward Europe.
As this water reaches higher latitudes, coolsbecomes denser and sinks. This deep, colder water, then return to the south along the ocean floor.
The Gulf Stream is one of the components of this system: this is the fast surface current that follows from the Gulf of Mexicoo along the east coast of the United States and then turns eastward in the Atlanticin the North Carolina area.
The concern is that AMOC will be vulnerable to decreasing salinity in the North Atlantic. As the Greenland ice melts and dumps more fresh water into the ocean, that water can dilute the salt water that normally sinks. Less sinking means less upheaval, which can weaken the entire circulation.
One of the most frustrating aspects of this story is that the direct measurements from AMOC are relatively recent., explains .
The flow has only been monitored continuously by instruments at anchor since 2004, which is not long enough to confidently distinguish a true long-term decline from natural fluctuations.
Some reconstructions, based on historical sea surface temperatures, suggest that the AMOC could have weakened by about 15% since 1950 — but these reconstructions are not equivalent to direct measurements.
The Utrecht team sought a different kind of race: if the AMOC weakens, will leave a mark elsewhere in the system?
In their simulations, the researchers concluded that a weakening of the AMOC should push the Gulf Stream north — that is, it would reach the coast of the United States further north before diverting towards the open Atlantic.
Professor van Westen stated that this hypothesis is attractive because the path of the Gulf Stream is something that can actually be monitored satellite, thus becoming a practical “indirect indicator” of changes in deeper circulation.
According to the study, the satellite signal already exists. The Gulf Stream appears to have moved north about 50 kilometers in the last 30 years.
Since this deviation coincides with what the physics-based model predicts during a weakening AMOC, this reinforces the hypothesis that the largest system ever is slowing downthe researchers point out.
The model points to a specific mechanism: the West Margin Deep Currenta cold, salty flow that runs south along the seafloor off North America, as part of the AMOC.
Under normal conditionsthis deep current flows under the Gulf Stream and exerts a kind of “southward pull” on it. But as AMOC weakens, this deep margin current also weakens. With less force to pull it down, the bend of the Gulf Stream gradually moves north.
The most dramatic result appears much later in the simulation. After centuries of gradual change, the Gulf Stream suddenly jumps more than 200 km to the north in just two years. About 25 years later, AMOC collapses into the model.
The implication is unsettling: a rapid and unusual change in the position of the Gulf Stream could be precursor to a collapse at a point of no returnoffering one of the clearest early warning indicators identified so far by scientists.
Van Westen said the key point is that this warning sign is simple to monitor: You can follow the path of the Gulf Stream from space, and if it suddenly jumps north, that could be a serious warning sign.
Previous investigations suggest that a collapse of AMOC could trigger a sharp cooling in parts of Europeeven in a warming world. Some models indicate that there could be episodes of extreme cold in winter, with cities like London occasionally approaching -20 °C.
The study also raises an uncomfortable point. If a sudden Gulf Stream jump is indeed a late warning sign, it may already be too late to halt the collapse — but there may still be enough time to prepare a response.
This could mean better thermal insulation of homes, strengthening infrastructure and a reassessment of areas where certain agricultural crops can grow reliably.
And if the Gulf Stream ever makes an abrupt leap north, the study suggests it could be the closest we have to a warning light intermittent to a major change in the Atlantic circulation — with serious consequences for Europe and other regions.
