Extreme coastal El Niño reduces ocean carbon outgassing off Peru

This is the authors' abstract. We don't add key points for this paper.

The southeastern tropical Pacific exhibits strong El Niño–Southern Oscillation (ENSO)‐driven interannual carbon variability. Previous studies have established carbon response to basin‐scale El Niño, but the response to coastal El Niño, a distinct mode confined to the Peruvian coast, remains poorly constrained. Using observation‐based p CO 2 products and a forced global physical‐biogeochemical ocean model at ~ 0.5° horizontal resolution, we quantify and decompose the carbon response to the 2017 coastal El Niño. During this event, nearshore CO 2 flux decreased by as much as 14.65 TgC yr −1 , comparable to the extreme basin‐scale events. This reduction was driven by weakened coastal winds that lowered gas transfer efficiency and suppressed upwelling of CO 2 ‐rich subsurface waters. Mean cross‐shore circulation further transported low‐ p CO 2 waters into the open ocean. This wind‐driven and spatially confined coastal pathway is distinct from basin‐scale El Niño, which suppresses outgassing through thermocline deepening, highlighting coastal El Niño as a distinct mode of carbon variability.