Poleward shift of AMOC source regions maintains stable supply of dense overflow waters to the North Atlantic Ocean

The Atlantic Meridional Overturning Circulation (AMOC), carrying warm, salty water to high latitudes, is a key component of the global ocean circulation with profound impacts on climate. To sustain the AMOC, dense-water formation at high northern latitudes, such as in the Nordic Seas and Arctic Ocean, is a requirement. Here, we use the high-resolution (1/12°) ocean reanalysis GLORYS12, corroborated by observations and other reanalyses, to show that a poleward expansion of warm Atlantic waters and corresponding sea-ice loss has caused a poleward shift of the dense water source regions in recent decades (1993-2020). This is manifested in enhanced surface water mass transformation in the Arctic Ocean, compensating for a reduction in the Nordic Seas. The associated strengthening of the Arctic Ocean overturning circulation has ensured that the transport of dense overflow waters across the Greenland-Scotland Ridge to the AMOC’s lower limb has remained stable. Our results thus provide evidence for a resilient northern overturning circulation in a warming climate.