Irreversibility of ocean oxygen loss after CO2 overshoot

durch Haichao Guo

Mittwoch 18.06.2025, 13:00 → 14:30 Europe/Berlin

8A-002 - Hörsaal Ostufer / Lecture Hall East (GEOMAR - Standort Ostufer / GEOMAR - East Shore)

The rapid ongoing ocean deoxygenation stemming from increasing atmospheric carbon dioxide (pCO₂) and associated climate change alters ocean biogeochemical cycles and threatens marine ecosystems. The capacity of oceanic oxygen inventories to recover after pCO₂ is restored to pre-industrial levels remains a critical and unresolved gap in climate mitigation research. Based on 6000-year simulations in an Earth System Model of intermediate complexity, we found that ocean deoxygenation is largely irreversible after CO₂ overshoot. This is driven by the redistribution of salinity in the ocean (fresher upper ocean and saltier deep ocean), which suppresses ocean ventilation and results in a -0.8\% (-2.0 Pmol) net loss of the oceanic oxygen inventory. -0.8 % oxygen loss is comparable with what we have today and our study reveals that after carbon overshoot, marine ecosystems may face long-term ocean deoxygenation.