Long-term trend of CO2and ocean acidification in the surface water of the Ulleung Basin, the East/Japan Sea inferred from the underway observational data

[摘要] Anthropogenic carbon is responsible for both global warming and oceanacidification. Efforts are underway to understand the role of ocean in a highCO₂ world on a global context. However, marginal seas received littleattention despite their significant contribution to biogeochemical cycles.Here we report the CO₂ increase and ocean acidification in the surfacewaters of the Ulleung Basin (UB) of the East/Japan Sea, and possible causesare discussed. Fourteen observations of surface fCO₂ were made in theperiod from 1995 to 2009. The contribution of temperature variation to theseasonality of fCO₂ was almost equivalent to the non-thermal effect inthe UB. However, the difference of relative contribution with the seasonmakes two seasonal peaks of fCO₂ in the surface water of the UB.Non-thermal effect contributed to the surface fCO₂ drawdown in summer,whereas the surface fCO₂ elevation in winter. The decadal trend offCO₂ increment was estimated by harmonic analysis. The estimated ratesof increase of fCO₂ were 1.8 ± 0.4 μatm yr⁻¹ forthe atmosphere and 2.7 ± 1.1 μatm yr⁻¹ for the surfacewater. The ocean acidification trend, calculated from total alkalinity andfCO₂, was estimated to be −0.03 ± 0.02 pH units decade⁻¹.These rates seem to be higher than observations at most other oceantime-series sites during the same period of time. Sustained observations arerequired to understand more accurate trend in this area.

[学科分类] 地球化学与岩石