A new study suggests the Atlantic Ocean’s critical heat-regulating current system is more unstable than previously believed, posing a significant threat to Europe’s climate. Researchers from the Netherlands found that a substantial weakening of the Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream, could plunge parts of the continent into a deep freeze, creating a cold anomaly on an otherwise warming planet. The analysis indicates that under certain global warming scenarios, winter temperatures in Northwestern Europe could plummet, with Arctic sea ice expanding to its shores.
The AMOC acts as a massive conveyor belt, redistributing heat throughout the ocean and playing a vital role in regulating the global climate. However, there is growing concern that this system is becoming more sensitive. As climate change accelerates the melting of the Greenland ice sheet and increases rainfall, the North Atlantic is being flooded with freshwater. This reduces the water’s salinity and density, hindering the sinking process of cold, salty water that drives the entire circulation, causing it to weaken.
In a recent study, researchers from the Royal Netherlands Meteorological Institute (KNMI) and Utrecht University used a highly complex climate model to investigate how Europe’s climate would be affected by a major slowdown of the AMOC. They simulated a more than 80% weakening of the circulation under both moderate and high future CO2 emission scenarios. This marks the first time a model of this complexity has been used to detail the potential temperature impacts of such a collapse triggered by global warming.
Under a moderate global warming scenario, the model showed that a weakened AMOC would result in significant regional cooling across Europe. This effect would be amplified by the southward expansion of the Arctic sea-ice pack, which could reach the coastlines of Britain, Scandinavia, and the Netherlands. As sea ice reflects far more sunlight than the ocean, its presence would cause winter temperatures in these regions to drop dramatically.
Conversely, in a high-emission scenario where global warming is more extreme, the impact on European temperatures would be less severe. Although an AMOC collapse is more probable under these conditions, the much warmer ocean temperatures would prevent sea ice from advancing as far south. As a result, the extreme cooling effect would be partially offset by the background global warming.
The potential temperature changes are stark. In the Netherlands, a cold extreme that currently occurs once every ten years could see temperatures drop to -20°C. Scotland could experience extremes as low as -30°C, with a city like Edinburgh facing nearly half the year with minimum temperatures below freezing. The Scandinavian climate would be transformed, with Norway’s typically mild west coast potentially seeing temperatures fall below -40°C. While Southern Europe would be less affected by the cold, the increased temperature contrast with the north could fuel more powerful winter storms and greater day-to-day weather volatility. Other consequences of a weaker AMOC include reduced precipitation in Europe and faster sea-level rise in the Atlantic.
https://www.uu.nl/en/publication/what-will-happen-to-europe-if-the-gulf-stream-weakens-significantly