Persistently strong oceanic CO2 sink in the western subtropical North Pacific

Abstract

The long-term trend of the partial pressure of CO2 in surface seawater (pCO2sea) in late-January to early-February during the past two decades was examined in the western North Pacific along the repeat line at 137°E from 3°N to 34°N. The growth rate of pCO2sea at each 1° in latitude ranged from +1.3 ± 0.2 to +2.1 ± 0.3 μatm yr-1, and the average was +1.7 ± 0.2 μatm yr-1. The growth of pCO2sea is attributable mainly to the uptake of anthropogenic CO2 in surface water and, to a small extent, to the regional changes in sea surface temperature (SST). The net air-to-sea CO2 flux in January-February that accounts for 40 to 60% of the annual flux remained at a similar level in the subtropical regions (7°N to 34°N). In the equatorial region (3°N to 6°N), however, a slight increase in the CO2 efflux was seen. Copyright 2005 by the American Geophysical Union.