Spatiotemporal variability of air–sea CO2 fluxes in response to El Niño-related marine heatwaves in the tropical Pacific Ocean Article Swipe
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· 2025
· Open Access
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· DOI: https://doi.org/10.1016/j.marenvres.2025.106949
· OA: W4406064517
The tropical Pacific is the largest oceanic source of carbon dioxide (CO<sub>2</sub>) emissions, where persistent marine heatwaves (MHWs) frequently occur. During persistent MHW events which are associated with strong El Niño events, CO<sub>2</sub> outgassing is notably reduced, however, its detailed spatiotemporal response to MHWs has not been fully characterized. In this study, we showed a high degree of consistency between CO<sub>2</sub> source regions in the central and eastern tropical Pacific Ocean and the occurrence regions with average annual MHW days exceeding 45 days (co-occurring area covers 80% of the area where MHWs occur). The spatiotemporal variability of the air-sea CO<sub>2</sub> flux on interannual and longer timescales can be reconstructed from annual MHW days and occurrence frequency, respectively, in the central and eastern Pacific Ocean of the co-occurring region. In this region, El Niño-related MHWs reduce the air-sea CO<sub>2</sub> flux density up to 0.4-0.8 molC/m<sup>2</sup>/yr per 100 MHW days, corresponding to a reduction of CO<sub>2</sub> emissions by approximately 0.1 PgC per 100 MHW days. This is a 10%-40% reduction in CO<sub>2</sub> emissions during MHW periods, with the strongest impact (30%-40% CO<sub>2</sub> emission reduction) in the equatorial Pacific (5°S-5°N) of the central and eastern Pacific Ocean. In contrast, air-sea CO<sub>2</sub> flux variations in coastal eastern upwelling region of the co-occurring region are mainly subjected to seasonal mixed layer variations, and thus not notably affected by El Niño-related MHWs on interannual timescales. By establishing the reproducibility between MHWs and air-sea CO<sub>2</sub> flux variations, our results pave a way for detailed future spatiotemporal evolutions of MHW-induced changes in air-sea CO<sub>2</sub> flux in the tropical Pacific Ocean.
