Carbon isotope measurements of atmospheric CO2 at a coastal station in Antarctica

A 3-years series of weekly 3-days integrated CO₂ samples analysed for ¹³C/¹²C isotopic ratio is presented, as well as a 2-years continuous sample series of 1-2 weeks integration time, analysed for ¹⁴C activity. The samples have been collected at the German Georg von Neumayer research station situated at the Antarctic coast at 70°s. 8°W. The ¹³C measurements show a slightly decreasing trend in δ¹³C of -0.038 * 0.009‰/year as is to be expected due to the global fossil fuel CO₂ release. A significant seasonal variation is not detectable in the ¹³C record. The δ¹⁴C activity of the atmospheric CO₂ samples is constantly lower by -11±2‰ if compared to the northern hemisphere clean air level. The opposite effect should be expected from an observed CO₂ concentration difference of about 3-4 ppm between the two hemispheres if due to ¹⁴C free fossil fuel CO₂. A total (supposedly regional) ¹⁴C depletion of about -20‰, to -25‰, compared to low latitudes in the southern hemisphere, can be attributed to exchange of atmospheric CO₂ with low ¹⁴C surface water (Δ¹⁴C = - 100‰,) due to upwelling in the circum polar region between 50°s and 70°s. This effect can qualitatively be reproduced by a simple one-dimensional atmospheric model.