Geothermal heating affecting ocean stratification and circulation after the Last Glacial Maximum

Geothermal heat flux through the seafloor is shown to influence the deep ocean's stratification during the Last Glacial Maximum (LGM, approximately 21,000 years ago). A fully coupled climate model indicates that geothermal heating leads to weaker density stratification, resulting in warmer, fresher deep waters, enhanced formation of Antarctic Bottom Water (AABW), and a deeper Atlantic Meridional Overturning Circulation (AMOC). These effects are linked to increased abyssal vertical mixing and altered sea-ice dynamics. In contrast, modern-day geothermal heating produces saltier AABW, driven by a different response of sea ice. By altering vertical mixing and sea-ice behavior, geothermal heating can have triggered the atmospheric CO2 release during the termination.