Variation of carbon dioxide partial pressure in the western North Pacific surface water during the 1982/83 El Niño event

To clarify the effect of oceanic condition on the pCO₂ in the surface sea water, observations of pCO₂ in the surface water of the western North Pacific were performed in January and February during the years from 1981 through 1985. An El Niño event occurred in the tropical Pacific Ocean from 1982 through 1983 and its effect was expected to appear in general oceanic conditions such as relatively low water temperatures, and high salinities in the surface sea water of the tropical and western region. Throughout the El Niño event, pCO₂ value in surface water in tropical and western region increased by up to 20 to 40 μatm above the normal values. Near the equator along the meridian of 137°E, it was found that a remarkable increase of pCO₂ was strongly correlated with the increase of salinity in the surface sea water. This finding could be related to eastward displacement of warm water and enhanced upwelling of subsurface water in this area. On the other hand, in the area from 14°N to 5.5°N along the meridian of 137°E, the pCO₂, and temperatures in the surface sea water, which were strongly correlated with each other, showed lower values than normal by up to 20 μatm and 1°C, respectively, in the year of the El Niño event. In the area from 14°N to 5.5°N, it was found that the variation of pCO₂ was stongly correlated with that of water temperatures, with a rate of about 4% pCO₂/°C.