- 1Institute for Chemistry and Biology of the Marine Environment, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany.
- 2Helmholtz Institute for Functional Marine Biodiversity (HIFMB) at the University of Oldenburg, Oldenburg, Germany.
- 3Department of Earth System Science, University of California Irvine, Irvine, CA, USA.
- 4Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, CA, USA.
The efficiency of the ocean to store atmospheric CO2 in the coming century strongly depends on the stability of marine carbon reservoirs. Marine dissolved organic carbon (DOC) contains more carbon than all living biomass on Earth combined (∼660 gigatons C) and is recalcitrant against remineralisation at a decadal to millennial timescale, which offers an additional carbon pump to sequester carbon from active air-sea gas exchange with a millennial-scale stability (microbial carbon pump). However, the fate of this key carbon reservoir in a changing future climate is unknown, because the impact of environmental controls on bacterial remineralisation of DOC to CO2 are not explicitly considered in global Earth System Models.
We developed a dynamical model for dissolved organic matter (DOM) that explicitly depicts the production of DOM through primary production and its degradation by heterotrophic microorganisms, and coupled it interactively to the marine biogeochemistry module of UVic ESCM, an Earth system model of intermediate complexity (EMIC). Being based on present-day simulations with the model, it is revealed that the factor that limits bacterial growth in the model and meta-genomic data indicating bacterial nutrient limitation show a similar pattern in the global ocean. Together with other experimental data, we suggest a strong link between the future developments of DOC and macronutrient cycles.
Our model indicates that an increase in the global DOC pool under global warming ranges from 17 to 42 gigatons C at the end of the 22nd century in a future simulation based on a high-emission scenario (SSP5–8.5). The estimated accumulation rate (2 GtC dec−1) is comparable to the amount of the terrestrial input of DOC to the ocean by rivers, underlining its quantitative relevance for the global DOC budget. Our results suggest that DOM-microbe interactions governed by bacterial nutrient limitation provide negative feedback on the climate state via DOC buildup, reinforcing the growth of DIC sequestration by the conventional biological pump (6 GtC dec−1 for > 1000 m depth) in the same simulation.
How to cite: Kurahashi-Nakamura, T., Dittmar, T., Martiny, A. C., and Lennartz, S. T.: Enhanced storage of carbon in marine dissolved organic matter in scenarios of global warming, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16067, https://doi.org/10.5194/egusphere-egu25-16067, 2025.
