Atmospheric CO2 concentrations and δ13C measurements along a hemispheric course (1998/99, Italy to Antarctica)

Continuous measurements of atmospheric CO2 concentrations were carried out along three ship-routes from Italy to Antarctica in 1994/95, 1996/97 and 1998/99. The growth rate of CO2 for four latitudinal belts with arbitrarily chosen boundaries (from 45°N to 80°S) is reported for the three expeditions. The northernmost belt shows the largest growth rate between 1996 and 1998 (close to 6 ppm/yr) while southern belts show an almost constant growth rate of 1.7 ppm/yr. Anthropogenic activities clearly affect both CO2 concentrations and growth rates. δ13C measurements were carried out on CO2 from 23 flask air samples collected during the 1998/99 expedition. Apart from negative values observed in highly polluted areas, a negative trend is observed across the Antarctic Convergence Area with no changes in the atmospheric concentration of CO2. The hypothesis of a biochemical origin of these light carbon isotope values is suggested.