Rapid increase of pCO 2 and seawater acidification along Kuroshio at the east edge of the East China Sea.

Rates of seawater acidification and rise of partial pressure of CO ₂ (pCO ₂ ) at ocean margins are highly uncertain. In this study, nine years of time-series data sampled during 2010-2018 along Kuroshio Current near the East China Sea (ECS) were investigated. We found trends of surface seawater pCO ₂ at 3.70 ± 0.57 μatm year ^-1 and pH at -0.0033 ± 0.0009 unityear ^-1 _, both of which were significantly greater than those reported from other oceanic time series. Mechanistic analysis showed that seawater warming caused rapid rates of pCO ₂ increase and acidification under sustained DIC increase. The faster pCO ₂ growth relative to the atmosphere resulted in the CO ₂ uptake through the air-sea exchange declining by ~50 % (~-0.8 to -0.4 mol C m ^-2  year ^-1 ) over the study period. Our results imply that rapidly warming boundary currents could potentially present an elevated pCO ₂ trend, leading to a gradual reduction and eventual loss of oceanic CO ₂ uptake under climate change.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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