Global Warming Weakens AMOC While Temporarily Strengthening Nordic Overturning Circulation

Ocean Science, 20 Apr 2026

Global warming and increased freshwater input from melting ice are weakening the Atlantic Meridional Overturning Circulation (AMOC), while initially strengthening the Nordic Overturning Circulation (NOC), which circulates water between the North Atlantic and Nordic Sea. This occurs because fresher, less dense water in the sub-polar North Atlantic weakens the AMOC by reducing the density difference with lower-latitude waters, while at the same time temporarily strengthening the NOC by increasing the density difference between the North Atlantic and Nordic Sea, increasing northward heat transport. For several decades, this stronger NOC may partially offset some regional cooling from a weakened AMOC by moving more heat northward. However, the study warns that if deep ocean convection (the sinking of cold, dense water that helps drive these currents) shuts down, both circulation systems could collapse. A shutdown could have major climate consequences, including cooler temperatures in Europe, more frequent extreme winter cold events, sea-level rise in North Atlantic coastal regions, and reductions in summer rainfall and crop productivity.

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