Variability of oceanic carbon cycle in the North Pacific from seasonal to decadal scales

摘要

Variability of upper-ocean carbon cycle in the North Pacific during 1958–2010 period is investigated using a physical-biogeochemical model. Comparisons with in situ data from five different oceanographic environments in the South China Sea, Monterey Bay, North Pacific gyre, northwestern Pacific, and Gulf of Alaska indicate that the model usually captures observed seasonal and interannual variability in both sea surface pCO_2 and sea-air CO_2 flux. Seasonal variability of pCO_2 and CO_2 flux in the North Pacific follows the change in sea surface temperature (SST) closely with high and low values in summer and winter, respectively. Total CO_2 modifies pCO_2 seasonal pattern in an opposite manner with respect to SST, and surface wind speed modifies the magnitude of CO_2 flux variations. On interannual and decadal time scales, sea surface pCO_2 is primarily controlled by anthropogenic CO_2, followed by modulations by the El Ni~no-Southern Oscillation and the Pacific Decadal Oscillation (PDO), while sea-air CO_2 flux is significantly regulated by the PDO and the North Pacific Gyre Oscillation (NPGO). We show that anthropogenic CO_2 tends to amplify the influence on CO_2 flux from the PDO but to damp the influence from the NPGO.