EVALUATION OF THE SOUTHERN OCEAN PCO_2 IN CMIP5 CARBON/CLIMATE COUPLED MODELS

摘要

Shipboard measurements and satellite-derived products are used to examine the meridional variations of surface water pCO_2 in Drake Passage. During austral winter, the observed pCO_2 equalibrates with the overlying atmo- sphere at the Polar Front (PF), suggesting no sea-to-air CO_2 flux in this region. These observations are used to evaluate eight available CMIP5 ESMs. Four of the eight ESMs show elevated pCO_2 near the PF, causing a signifi- cant sea-to-air CO_2 flux. Winds in these models are gen- erally stronger than the scatterometer winds, magnifying the sea-to-air CO_2 flux in addition to upwelling rich Dis- solved Inorganic Carbon (DIC) to the surface and driving stronger equatorward Ekman currents. Surface equator- ward ocean currents in the models are much stronger than satellite-derived currents, implying too week poleward eddy-driven currents to compensate the stronger equator- ward Ekman currents. Because of the strong stratification in some of these ESMs, the strong equatorward surface currents advect the upwelled DIC out of the Drake Pas- sage. This, together with the significant sea-to-air CO_2 flux, is likely to reduce the DIC inventory in Drake Pas- sage.