Reconstruction of the atmospheric CO2 concentration history from an Antarctic deep ice core, Dome Fuji using a wet extraction technique: analysis procedures,dating of air in ice and concentration variations (scientific paper)

摘要

In order to deduce the atmospheric CO2 concentration variations over the past 320 kyr, air samples were extracted from the Dome Fuji deep ice core using a wet extraction method, and their CO2 concentration values were determined with a reproducibility of 1.0 ppmv. By measuring the CO2 concentrations of firn air samples collected at Dome Fuji, it was found that the effective bubble close-off depth can be defined by the mid-point of the close-off zone. For dating the air in the ice core, the age difference between ice and air (Δage) was estimated by using a densification model to be between 1000 and 5000 years, showing small and large values during the interglacial and glacial periods, respectively, due primarily to variations of precipitation. The CO2 concentration variations with a mean time resolution of about 1.1 kyr over the last three glacial-interglacial cycles showed a good correlation with those of δ18O, which suggests that the Southern Ocean played an important role in the variation of the atmospheric CO2 concentration during the last three glacial-interglacial cycles.