Earth’s Hidden Ocean Thermostat Kept Climate in a Life-Friendly Range
Geologists propose a long-running feedback among sea level, ocean phosphate, oxygen levels, and the burial of organic carbon in sediments helped stabilize Earth’s climate for about 60 million years. High sea levels trap phosphate on shelves, reducing marine productivity and carbon burial, keeping atmospheric CO2 high; lower sea levels release more phosphate, boosting life and increasing carbon burial, which lowers CO2 and cools the planet. The strongest burial occurs in a narrow sea-level window (~10–40 meters above today), and over time shifting oxygen minimum zones narrowed this window, contributing to the climate’s resilience.