Rapid increase of pCO₂ and seawater acidification along Kuroshio at the east edge of the East China Sea

Rates of seawater acidification and rise of partial pressure of CO₂ (pCO₂) 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 pCO₂ 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 pCO₂ increase and acidification under sustained DIC increase. The faster pCO₂ growth relative to the atmosphere resulted in the CO₂ 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 pCO₂ trend, leading to a gradual reduction and eventual loss of oceanic CO₂ uptake under climate change.