pCO2 and δ13C in the air and surface sea water in the western North Pacific

In order to ascertain yearly variability, the pCO₂ in the air and surface sea water was measured during the winter season in and over the western North Pacific from 1981 to 1985, and δ¹³C measurements were taken from 1982. The seasonality was also studied in the area off Japan’s coast. The distribution of pCO₂ in the surface sea water was found to vary with geographical location; it is low in the mid-latitudes and high in the equatorial region. During the El Niño Event in 1982/1983, the horizontal distribution of pCO₂ was greatly disturbed, with a relatively low temperature and a high pCO₂ level in the equatorial region in the western North Pacific.

Surface sea water in the temperate zone shows a seasonal variation in pCO₂, which is low in winter and high in summer.

It was found that pCO₂ in the air over the ocean decreases with distance from the Japanese islands, and south of 15°N it is nearly constant. Between 1982 and 1985, the δ¹³C of CO₂ in the air south of 15°N decreased at 0.022 ± 0.006%, yr^-1 and the pCO₂ increased at 1.11 ± 0.04 ppm yr^-1. The secular variation of pCO₂ and δ¹³C in the surface sea water with the CO₂ increase in the air, was not ascertainable from observations from 1981 to 1985.