[AAS07-P04] 西太平洋における表層水のCO2分圧および大気海洋間CO2フラックスの変動
キーワード：CO2分圧、太平洋、ENSO
Temporal and spatial variations of CO2 partial pressure in surface sea water (pCO2,sea) observed in the western Pacific were analyzed in terms of physics and chemistry of the ocean and the CO2 fluxes between the atmosphere and ocean were also evaluatedand the CO2 flux between the atmosphere and ocean . The pCO2,sea has been observed continuously on-board a cargo ship “Trans Future 5” on her round-trip between Japan and Australia. Systematic observations for the atmospheric pCO2 (pCO2,air) were have been also conducted in the western Pacific by a grab-sampling method using container ships sailing almost similar route.
In the equatorial region, interannual variabilities of pCO2,sea were clearly observed, and were highly correlated with the El Niño Southern Ocsillation (ENSO). Higher pCO2,sea observed in 2008 and 2012, coincident with La Nina, could be caused by transport of high salinity, low temperature and high dissolved inorganic carbon water upwelled off the coast of Peru to the observation line at the western Pacific Ocean. When large and strong El Nino occurred from 2015 to 2016, significant increase of pCO2,sea was observed between 25°N and 25°S. The pCO2,sea increase could be associated with remarkable decrease of the precipitation observed in the western Pacific region.
The CO2 flux between the atmosphere and the ocean was calculated by using the air-sea pCO2 difference in pCO2 (DpCO2) between the atmosphere and the surface ocean, sea surface temperature and wind speed at 10m height. In the western Pacific Ocean, the largest CO2 absorption was found at 20°S (−13.0 gC m-2 yr-1), and the net CO2 outgassing at equatorial area (1.2 gC m-2 yr-1) were found.
The increase in pCO2,sea associated with the strong El Niño event in 2015 and 2016 may have caused a decrease in the oceanic CO2 absorption throughout the western Pacific.
In the equatorial region, interannual variabilities of pCO2,sea were clearly observed, and were highly correlated with the El Niño Southern Ocsillation (ENSO). Higher pCO2,sea observed in 2008 and 2012, coincident with La Nina, could be caused by transport of high salinity, low temperature and high dissolved inorganic carbon water upwelled off the coast of Peru to the observation line at the western Pacific Ocean. When large and strong El Nino occurred from 2015 to 2016, significant increase of pCO2,sea was observed between 25°N and 25°S. The pCO2,sea increase could be associated with remarkable decrease of the precipitation observed in the western Pacific region.
The CO2 flux between the atmosphere and the ocean was calculated by using the air-sea pCO2 difference in pCO2 (DpCO2) between the atmosphere and the surface ocean, sea surface temperature and wind speed at 10m height. In the western Pacific Ocean, the largest CO2 absorption was found at 20°S (−13.0 gC m-2 yr-1), and the net CO2 outgassing at equatorial area (1.2 gC m-2 yr-1) were found.
The increase in pCO2,sea associated with the strong El Niño event in 2015 and 2016 may have caused a decrease in the oceanic CO2 absorption throughout the western Pacific.