The concentration of atmospheric carbon dioxide at the Japanese Antarctic Station, Syowa

Abstract

Precise and continuous measurements of the atmospheric CO2 concentration have been made at Syowa Station, Antarctica since February 1984. The diurnal CO2 variation was hardly observable throughout the year. The secular CO2 trend was variable with time, showing slow increase in 1984, 1986 and 1988 and rapid increase in 1985 and 1987. The annual CO2 increase was especially large in 1987, which may be related to the 1986/1987 ENSO event. The average rate of annual CO2 increase over the last 5 years was about 1.6 ppmv yr-1. The average seasonal CO2 cycle showed minimum and maximum concentrations in mid-April and early in October, respectively, and its peak-to-peak amplitude was about 1.1 ppmv. The measured seasonal cycle was variable from year to year, but there was no indication of a long-term increase of the amplitude. It was found that irregular CO2 variations with amplitudes of 0.2 ppmv at most and periods of a few weeks show high correlation with airmass exchange by synoptic scale weather disturbances. The results from Syowa are compared with those from the South Pole and Cape Grim, Tasmania.