Polar and subpolar shelf seas dominate enhanced coastal CO<sub>2</sub> uptake during marine heatwaves.
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- Record sourced from PubMed, PMID 42680758.
- Also identified by DOI 10.1038/s41467-026-77165-0.
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Abstract
Marine heatwaves (MHWs) perturb air-sea CO<sub>2</sub> fluxes, but their cumulative impact on the global coastal carbon sink remains poorly understood. Using four observation-based CO<sub>2</sub> flux datasets, with priority given to a global coastal product, we find that MHWs enhance net CO<sub>2</sub> uptake in global shelf seas by 11.0 ± 1.6% from 1985 to 2020, in contrast to reduced uptake in the open ocean. The enhancement is largely attributable to polar and subpolar shelf seas, where frequent MHWs coincide with sea-ice loss and non-thermal reductions in dissolved inorganic carbon (DIC), outweighing reduced uptake or enhanced outgassing in lower-latitude, warming-dominated regions. Analysis with a global ocean biogeochemical model suggests that the observed DIC reductions are largely linked to enhanced biological carbon fixation. Our findings reveal region-specific MHW impacts on coastal carbon dynamics, highlighting a critical role of high-latitude shelf systems in the global carbon budget under ongoing climate change.