A new study revealed the principal ocean current in the Atlantic Ocean which includes the Gulf Stream could collapse as early as two years from now. When it happens, it would destroy marine ecosystems and cause mass weather disruptions.
Surface temperatures in the western North Atlantic Ocean area, including the Gulf Stream. Colder areas such as landmasses are in blue, hotter areas are in red. Image: NASA
The study, an updated look at how global heating due to the climate crisis has raised temperatures in the Atlantic Ocean and stratified the thermal profile of those waters, paints a terrifying picture of what could happen to currents there by 2025.
Ocean currents on the planet have continued to flow in the same way for all human history and long before that. Though there are always minor variations in the timing of the cycles and precisely where the water moves, waters in the large open seas of all oceans have always been in motion, in directions dictated by the principles of thermodynamics and pressures caused by the Earth’s rotation.
One of the most important of those oceanic currents, in terms of the physics of its movement, the impact it has on all major weather patterns throughout its transit, is the Atlantic Meridional Overturning Circulation (AMOC) current. It incorporates within it the Gulf Stream, a fast-moving warm water flow which begins its journey in the Gulf of Mexico, passes through the Florida straits in the Caribbean, then turns northwards along the southern East Coast of the United States. It eventually takes a sharp turn east approximately around 36° N latitude, just off the coast of North Carolina. From there it moves outwards toward Northwest Europe, where it splits. Part of it eventually becomes the North Atlantic Current and feeds into that flow, and another part moves southward as the Canary Current, where it recirculates off the West African coastline.
Computer models provided by NASA and NOAA are now providing a far more accurate model of how the Atlantic Meriodional Overturning Circulation current moves. Image: NOAA's Atlantic Oceanographic and Meteorological Laboratory
The AMOC current naturally flows northwards, bringing the hotter waters from the equator upwards toward the cooler regions in the north. The rotational motion of the Earth is responsible for causing the AMOC to twist towards Europe as it moves northwards. There, at the end of the current’s travels, cold water from underneath gets pushed upwards from physical forces and the hot water is pulled underneath, where it cools prior to the water once again heading southwards to complete the AMOC cycle.
Based on updated research directed by researchers Peter Ditlevsen of the Niels Bohr Institute and Susanne Ditlevsen of the Institute of Mathematical Sciences, with both groups part of the University of Copenhagen, Denmark, this natural motion of currents may be about to come to a crashing halt.
The timing of that halt is still in question. But based on already-observed braking in the rate of flow of the Gulf Stream which shows at its lowest speed in a minimum of 1,600 years, the accelerating superheating of all oceanic waters thanks to global heating due to the climate crisis, and the lesser amount of churning in the Atlantic ocean waters which mixes up cold waters from underneath with the hotter ones on top, estimates which once put the shutdown of the AMOC current to occur only by the end of the century have moved that up to almost certainly by 2050.
The new study by the University of Denmark researchers is now pulling that even closer at hand, to possibly as early as 2025.
The projection that the AMOC could slow to almost no movement in just two years is based in part on new data showing the far more rapid melting of the glaciers and ice cap of Greenland in recent years. Those in turn have been strongly impacted by the formation of more widespread and long-lived heat domes over the Arctic, which are reinforced in their own circulatory patterns by induced shifts in the northernmost jet streams high above the surface of the Earth.
As these and other researchers looking at the same AMOC stoppage scenario have indicated, despite that the AMOC is theoretically just a localized phenomenon, its impacts would extend far beyond its direct geographic borders. That is because the waters from the AMOC currents normally flow into others and no longer do so soon.
As an example of what will occur when the AMOC stops moving, one of the most dramatic effects will happen along the U.S. East Coast. Sea levels there will rise disproportionately and faster as larger volumes of water that would normally spread across the Atlantic are retained closer to land. As that happens, the lack of warm equatorial waters pushed towards Europe will cause average temperatures to fall there. While lower temperatures might ease some of the current heat wave phenomena spreading across the European continent, those thermal shifts are also expected to cause new and more treacherous oceanic storms in that part of the world.
Further south, as the AMOC’s recirculation of cooler waters from the north into the Canary Current which originates off the coast of Africa, temperatures will rise in those waterways. That will contribute to more tropical storms and powerful hurricanes spinning off the West African coastlines every year. It will also spawn another oceanic current pattern which is expected to flow further southwards, It would likely bring far more powerful tropical storms to countries to Venezuela and Brazil in Latin America, threatening the Amazon rainforest regions in ways they have not experienced in modern times.
Eventually those new hotter southwards currents will have additional serious implications for the already endangered Antarctic ice sheets at the South Pole. The hotter tropical waters will begin to flow southwards and are expected to raise temperatures in the seas just north of Antarctica, and force faster melting in the Antarctic.
Beyond just the water impacts, the damage to marine life throughout the AMOC current path would be catastrophic. Everything from phytoplankton to fish in more northern waters often caught for food, and to the largest of whales, would see their natural ecosystems fractured beyond repair. The higher temperatures alone would also drive many species to extinction.
Professor Peter Ditlevsen, the first-named author in the new study from the University of Copenhagen, warned of how badly this could affect so much of the normal planetary functions, and for life itself.
“I think we should be very worried,” he said in an interview about the new paper. “This would be a very, very large change. The AMOC has not been shut off for 12,000 years.”
The Potsdam Institute for Climate Impact Research’s Professor Niklas Boers, who led a team researching some of the same phenomena about eventual decline of the AMOC and published a paper on it in 2021, commended the new research for validating his group’s early conclusions.
“The results of the new study sound alarming but if the uncertainties in the heavily oversimplified model [of the tipping point] and in the underlying [sea temperature] data are included, then it becomes clear that these uncertainties are too large to make any reliable estimate of the time of tipping,” he said.
The paper summarizing the latest research study on the AMOC current and the Gulf Stream, “Warning of a forthcoming collapse of the Atlantic meridional overturning circulation,” published by Peter Ditlevsen and Susanne Ditlevsen, was published in the peer-reviewed journal Nature Communications, on July 25, 2023.