Seasonal and inter-annual variations in pCOsea2 and air-sea CO2 fluxes in mid-latitudes of the western and eastern north pacific during 1999-2006: Recent results utilizing voluntary observation ships

We have investigated the seasonal and inter-annual variations of the difference in partial pressure of co2 between surface seawater (pcosea2) and overlying air (pcoair2) and the air-sea co2 flux in the mid-latitudes of the western north pacific (wnp; 25-40°n,140-170°e) and eastern north pacific (enp; 25-40°n,120-150°w) from 1999 to 2006 using the latest voluntary observation ship data. in the wnp and enp,the area-averaged δpco2 (pcoair2 - pcosea2) was at its minimum in late summer (-4.6 to 6.7 μatm in the wnp and -32.5 to -20.5 μatm in the enp) and at its maximum in late winter (51.0 to 59.8 μatm in the wnp and 35.1 to 46.2 μatm in the enp). the wnp acts as a moderate sink for atmospheric co2 (4.1 to 5.5 mmol m-2 d-1),while the enp acts as a weak sink (1.1 to 1.9 mmol m-2 d-1). because δpco2 is mainly controlled by pcosea2,we have evaluated the effect of the factors controlling pcosea2: sea surface temperature (sst),salinity (sss),dissolved inorganic carbon (tco2),and total alkalinity (at). in the wnp,not only sst but also tco2 plays an important role in the seasonal pcosea2 variation,while the sst could only explain most of the pcosea2 variation in the enp. from 1999 to 2006,pcosea2 increased at a significantly lower rate (0.53±0.11 μatm yr-1) than pcoair2 (1.81±0.01 μatm yr-1) in the wnp,and at a slightly lower rate in the enp (1.32±0.16 μatm yr-1). the air-sea co2 flux increased at a rate of 0.19±0.05 mmol m-2 d-1 yr-1 in the wnp and 0.09±0.03 mmol m-2 d-1 yr-1 in the enp,suggesting that the wnp is a stronger sink for atmospheric co2 © 2010,meteorological society of japan.