Data-based estimates of the ocean carbon sink variability–first results of the Surface Ocean pCO2 Mapping intercomparison (SOCOM)

[摘要] Using measurements of the surface-ocean CO₂ partial pressure(pCO₂) and 14 different pCO₂ mapping methods recently collated bythe Surface Ocean pCO₂ Mapping intercomparison (SOCOM) initiative,variations in regional and global sea–air CO₂ fluxes are investigated.Though the available mapping methods use widely different approaches, we findrelatively consistent estimates of regional pCO₂ seasonality, in linewith previous estimates. In terms of interannual variability (IAV), allmapping methods estimate the largest variations to occur in the easternequatorial Pacific. Despite considerable spread in the detailed variations,mapping methods that fit the data more closely also tend to agree moreclosely with each other in regional averages. Encouragingly, this includesmapping methods belonging to complementary types – taking variability eitherdirectly from the pCO₂ data or indirectly from driver data viaregression. From a weighted ensemble average, we find an IAV amplitude of theglobal sea–air CO₂ flux of 0.31 PgC yr⁻¹ (standard deviationover 1992–2009), which is larger than simulated by biogeochemical processmodels. From a decadal perspective, the global ocean CO₂ uptake isestimated to have gradually increased since about 2000, with little decadalchange prior to that. The weighted mean net global ocean CO₂ sinkestimated by the SOCOM ensemble is −1.75 PgC yr⁻¹ (1992–2009),consistent within uncertainties with estimates from ocean-interior carbondata or atmospheric oxygen trends.

[学科分类] 地球化学与岩石