Increasing atmospheric CO2 enhances the carbon uptake of the coastal ocean

Observational reconstructions indicate a contemporary increase in coastal ocean CO2 uptake. However, the mechanisms and their relative importance in driving this globally intensifying absorption remain unclear. Here we integrate coastal carbon dynamics in a global model via regional grid refinement and enhanced process representation. We find that the increasing coastal ocean CO2 uptake is primarily driven by the upper ocean-atmosphere equilibration lag (41%), followed by climate-induced changes in the circulation (36%) and increasing riverine nutrient loads (23%). The comparatively weak riverine impact is mediated by enhanced advective export of organic carbon across the shelf break, thereby further adding to the carbon enrichment of the open ocean. The contribution of biological carbon fixation increases as the coastal ocean capacity to hold CO2 decreases under continuous climate change and ocean acidification. Our seamless coastal ocean integration advances carbon cycle model realism, which is relevant for addressing impacts of climate change mitigation efforts.

Mathis M., Lacroix F., Hagemann S., Nielsen D., Ilyina T. & Schrum C., 2023. Increasing atmospheric CO2 enhances the carbon uptake of the coastal ocean. Research Square. Article.

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