Rising Temperatures Expected to Weaken Major Polar-driven Ocean Circulation Systems

Nature and Environmental Research Letters, 26 February and 3 March 2025

Two recent studies refine predictions of North Atlantic and Antarctic ocean circulation behavior this century, highlighting the interconnectedness of the Earth’s polar oceans and climate system. Together, the studies emphasize the urgent need for mitigation of emissions, to avoid major disruption to the delicate balance of heat transport and carbon uptake regulated via the polar oceans.

In the first study, researchers analyzed 34 climate model simulations of the Atlantic Meridional Overturning Circulation (AMOC), experimenting with the freshening of the North Atlantic and high emissions scenarios. They found that the AMOC is unlikely to fully collapse by the end of the century. Increased greenhouse emissions however would likely dramatically weaken the AMOC, spurred by increased freshwater from the melting Greenland Ice Sheet; but Southern Ocean winds have the ability to sustain this major circulation system even in its weakened state, preventing it from stalling completely. The research points to the potential for formation of overturning circulation systems in the Pacific – a necessary counterbalance to AMOC weakening. The AMOC provides a vital source of heat and nutrients to Europe and the North Atlantic; its collapse would have severe consequences for climate, precipitation patterns, and ecosystems across parts of Europe, South America and Africa.

In the second study, researchers predict that under a high emissions scenario, the world’s strongest ocean current, the Antarctic Circumpolar Current (ACC), will weaken 20% by 2050. The ACC serves as a conduit between the Earth’s ocean basins and is linked with the AMOC via the Atlantic Ocean. Its strength therefore influences global heat and nutrient transport, as well as carbon uptake. Increased melt from the Antarctic Ice Sheet would likely weaken the ACC and produce cascading effects on other major ocean circulation systems.

Decline of Antarctic Circumpolar Current: https://iopscience.iop.org/article/10.1088/1748-9326/adb31c
Weakening Atlantic Meridional Overturning Circulation: https://www.nature.com/articles/s41586-024-08544-0
News and Views: https://www.nature.com/articles/d41586-025-00300-2