Recent deceleration of oceanic pCO2 increase in the western North Pacific in winter

Abstract

Recent changes in oceanic CO2 partial pressure (pCO 2sea) have attracted increasing interest as they relate to the increase in atmospheric CO2 and climate change. We report decadal changes in the growth rates of pCO2sea in latitudinal zones from 3°N to 33°N along the repeat hydrographic line at 137°E in the western North Pacific in winter. The growth rates of pCO 2sea for 1999-2009 (-0.3 0.9 [mean 1σ] to 1.7 ± 0.5 μatm yr-1) were lower than those for 1984-1997 (0.7 ± 0.3 to 2.2 ± 0.6 μatm yr-1) at most latitudes, indicative of the recent notable deceleration of pCO2sea increase. For latitudes around 10-20°N, we attribute the reduction in the growth rate of pCO2sea for 1999-2009 primarily to the reduction in the contribution from dissolved inorganic carbon (DIC) originating from a reduction in carbon accumulation associated with the expansion of the western Subtropical Gyre towards the south. © 2012. American Geophysical Union. All Rights Reserved.