Rising Temperatures and Antarctic Ice Loss Produce First Sign of Slowing Global Ocean Circulation

Communication Earth & Environment, 13 March 2023

This study combines historical measurements with climate models to reveal that global meridional overturning circulation (GMOC) patterns — the planet-wide system of large ocean currents — have weakened by up to 20% over the last five decades near the seafloor around Antarctica. As temperatures rise, warm meltwater from West Antarctica flows into the Amundsen, Bellingshausen and Ross seas where it slows the formation of cold bottom water. Without these bottom waters, global ocean circulation patterns will destabilize and extreme weather globally can become more frequent. While lower Southern Ocean circulation has slowed, currents closer to the surface are gaining strength. Together, these two changes may also decrease the Southern Ocean’s ability to draw CO2 from the atmosphere, and begin to trigger a cascade of similar changes in the neighboring South Atlantic and Indo-Pacific oceans. Unless emissions are reduced, the GMOC is projected to experience a large-scale slowdown as rising temperatures prevent mixing between ocean layers, disrupting the movement of heat, nutrients, and carbon between hemispheres.

https://www.nature.com/articles/s43247-023-00727-3