A patch of cooling ocean south-east of Greenland, known as the cold blob, is likely caused by a slowdown in the Atlantic Meridional Overturning Circulation, according to new research. The findings add to concerns about potential future climate impacts in Europe and beyond. Scientists remain divided on the exact causes.
Over the past 150 years, one area south-east of Greenland has cooled by up to 1°C while the rest of the planet has warmed. Researchers led by Stefan Rahmstorf at the Potsdam Institute for Climate Impact Research used climate reanalyses based on satellite, buoy and ship data to examine the phenomenon. Their analysis showed reduced heat loss from the ocean surface since 1955 and cooling extending 1000 metres deep. This points to the AMOC transporting less heat northward rather than atmospheric factors like winds or clouds being the main driver. Other studies have reached different conclusions. A 2022 analysis by Chengfei He attributed the cooling mainly to a northward shift in the jet stream, while a 2021 study found stronger winds explained most of the effect. Rahmstorf said winds and clouds account for only a modest fraction of the cold blob. The research raises the possibility that the nearby subpolar gyre could pass a tipping point as early as the 2040s, potentially cooling parts of western Europe more rapidly than a full AMOC collapse. Experts note that limited data means alternative explanations cannot yet be ruled out.