Observed Regional Impacts of Marine Heatwaves on Sea‐Air CO₂ Exchange

Abstract Marine heatwaves (MHWs) have devastating effects on ecosystems. Yet a global assessment of the regional impacts of MHWs on the sea‐air exchange is missing. Here, we analyze 30 global observation‐based sea‐air flux data sets from 1990 to 2019. Globally, the oceanic uptake is reduced by 8% (3%–19% across data sets) during MHWs. Regionally, the equatorial Pacific experiences a 31% (3%–49%) reduction in release and MHWs often coincide with extreme sea‐air flux anomalies in this region. The oceanic uptake decreases during MHWs by 29% (19%–37%) and 14% (5%–21%) in the low‐to‐mid latitude Northern and Southern Hemisphere, respectively. Reduced dissolved inorganic carbon in the tropics weakens outgassing, while high ocean temperatures diminish uptake in the low‐to‐mid latitudes. In the subpolar North Pacific and Southern Ocean, enhanced carbon uptake occurs during MHWs, but uncertainties in p data sets limit a comprehensive assessment in these regions.