Biologically processed carbon drives the annual marine carbon sink over centuries after CO2 emissions cease

durch Dr. Wolfgang Koeve (GEOMAR, BM)

Mittwoch 15.04.2026, 13:15 → 14:30 Europe/Berlin

5-1.213 - PAZIFIK / PACIFIC- Rechte Seite - Großer, unterteilbarer Konferenzraum (GEOMAR - Standort Ostufer / GEOMAR - East Shore)

Abstract
Physical-chemical uptake has dominated the ocean‘s uptake of carbon since preindustrial times. However, it remains unclear how the ocean carbon uptake will evolve after emissions cease and which mechanisms will drive these changes. Here we use Earth System models to study the evolution of the annual growth rate of the marine carbon uptake under ambitious CO2 mitigation scenarios that achieve net zero CO2 emissions within the upcoming decades. With net zero emissions, we find a rapid shift of the processes that govern the growth rate of marine carbon uptake. The physical- chemical uptake of anthropogenic CO2 decreases in response to decreasing atmospheric CO2. In contrast to the decreasing physical- chemical uptake, we observe a growing relevance of carbon uptake attributable to the biological carbon pump (DICremin). The time elapsed between turning net-zero and when marine carbon uptake is dominated by biological pump carbon (δDICremin > 0.5*δDIC) scales with cumulative CO2-emissions since pre-industrial times. For scenarios with global warming targets of around +1.5°C, this point may be reached already around the turn of this century.
Exploring further what drives the increasing contribution of the biological carbon pump, i.e., the ‘gain’ versus the ‘loss’ side (Frenger et al., 2024, https://doi.org/10.1111/gcb.17124) of DICremin, we find in output from CMIP6 models (Wilson et al., 2022, https:// doi.org/10.1073/pnas.2204369119) that the increase in the biological pump carbon is driven by an overall slowing down of the ocean circulation leading to less re-emergence of DICremin at the ocean surface and a higher accumulation of DICremin below the surface ocean. This increase in DICremin is partly offset by a projected decrease in the export of organic matter into the interior ocean.

Seminar link
https://geomar.webex.com/geomar/j.php?MTID=ma522f5f4b0af40855947a88dcf5482d3