Temporal variations of atmospheric CO2 concentration and carborn isotope ratio in Ny-Alesund, Svalbard

Ground based observation of the atmospheric CO_2 concentration and its carbon isotope, δ^C, have been performed in Ny-Ålesund, Svalbard since 1991. The CO_2 concentration and δ^C observed in 1991-1999 showed clear seasonal cycles with peak-to-peak amplitudes of 16.5‰ ppmv and 0.8,respectively. From comparison of the seasonal cycles, it was found that the seasonal CO_2 cycle in Ny-Ålesund is mainly caused by seasonal change of biospheric activities. Interannual variations of the CO_2 concentration and δ^C superimposed on their secular trends were also observed. Comparing both of the interannual variations revealed that the cause was primarily ascribed to the imbalance of the CO_2 exchange between the atmosphere and the terrestrial biosphere