Air–sea CO2 fluxes in the East China Sea based onmultiple-year underway observations

[摘要] This study reports the most comprehensive data set thus far of surface seawaterpCO₂ (partial pressure of CO₂) and the associated air–sea CO₂fluxes in a major ocean margin, the East China Sea (ECS), based on 24 surveysconducted in 2006 to 2011. We showed highly dynamic spatial variability insea surface pCO₂ in the ECS except in winter, when it ranged across a narrowband of 330 to 360 μatm. We categorized the ECS into five differentdomains featuring with different physics and biogeochemistry to bettercharacterize the seasonality of the pCO₂ dynamics and to betterconstrain the CO₂ flux. The five domains are (I) the outer Changjiangestuary and Changjiang plume, (II) the Zhejiang–Fujian coast, (III) thenorthern ECS shelf, (IV) the middle ECS shelf, and (V) the southern ECSshelf. In spring and summer, pCO₂ off the Changjiang estuary was as lowas < 100 μatm, while it was up to > 400 μatm inautumn. pCO₂ along the Zhejiang–Fujian coast was low in spring, summer andwinter (300 to 350 μatm) but was relatively high in autumn (> 350 μatm). On the northern ECS shelf, pCO₂ in summer and autumn was> 340 μatm in most areas, higher than in winter and spring.On the middle and southern ECS shelf, pCO₂ in summer ranged from 380 to400 μatm, which was higher than in other seasons (< 350 μatm). The area-weighted CO₂ flux on the entire ECS shelf was−10.0 ± 2.0 in winter, −11.7 ± 3.6 in spring, −3.5 ± 4.6 insummer and −2.3 ± 3.1 mmol m⁻² d⁻¹ in autumn. It is importantto note that the standard deviations in these flux ranges mostly reflect thespatial variation in pCO₂ rather than the bulk uncertainty.Nevertheless, on an annual basis, the average CO₂ influx into theentire ECS shelf was 6.9 ± 4.0 mmol m⁻² d⁻¹, about twice theglobal average in ocean margins.

[学科分类] 地球化学与岩石