A new scientific assessment shows that the key ocean system in the Atlantic Ocean - the Atlantic Meridional Overturning Circulation (AMOC) - is significantly closer to collapse than previously thought, with the consequences of such a scenario being catastrophic for Europe, Africa and the Americas, writes "The Guardian".
The system, which carries warm waters from the tropics to Europe and the Arctic, also includes the well-known Gulf Stream, which is its surface part. It is through it that the warm waters reach the North Atlantic, where they cool and sink, driving the deep circulation. The AMOC is now at its weakest in about 1,600 years due to climate change.
The new study finds that the climate models that predict the most severe slowdown are actually the closest to reality. According to the scientists, this means that by the end of the century the AMOC could slow by between 42% and 58% - a level that almost inevitably leads to collapse.
The study combines real ocean observations with climate models, thereby significantly reducing the uncertainty in the predictions. Lead author Dr Valentin Portmann from the Inria research center in France says that the system is weakening more than expected and is approaching a critical point. Prof. Stefan Rahmstorff from the Potsdam Institute for Climate Impact Research stresses that the "pessimistic" scenarios now look the most realistic and warns that the point of irreversible collapse could be reached as early as the middle of this century.
A collapse of the AMOC would have severe global consequences - from a shift in the tropical rainfall belts on which millions of people depend for agriculture, to extremely cold winters and droughts in Western Europe. In addition, sea levels in the Atlantic region could rise by an additional 50 to 100 centimeters.
Scientists explain that the slowdown in the current is associated with rapid warming in the Arctic, which changes the density of ocean waters and makes it difficult for them to sink - a key mechanism for the functioning of the system. An additional factor is the melting of the Greenland ice sheet, which is bringing freshwater into the ocean and further weakening the circulation - an effect that is not even fully accounted for in current models.
The new study, published in the journal Science Advances, uses advanced statistical methods to identify the most reliable climate models. According to experts, even without a complete collapse, a significant weakening of the AMOC in the coming decades now seems almost certain and would have serious consequences for global climate.