Impact of atmospheric CO2 doubling on the North Pacific Subtropical Mode Water

In order to investigate responses of the North Pacific Subtropical Mode Water (NPSTMW) to climate change, the impact of atmospheric CO2 doubling with 1% annual increase is examined using a coupled climate model (GFDL CM2.1). Under the CO2 forcing, the surface waters in the formation region of NPSTMW and the core layer of NPSTMW become warmer and freshener. The total volume of NPSTMW increases by about 40% due to warming. The inter‐annual and decadal variability of NPSTMW is significantly correlated with the variability of the Kuroshio heat transport, and less correlated with variability of sea surface temperature and winter monsoon index in comparison with the control run.