Carbon isotope measurements of atmospheric C02 at a coastal station in Antarctica

A 3-years series of weekly 3-days integrated COz 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 'T 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 "C measure-ments show a slightly decreasing trend in 6°C of-0.038 * 0.009%,/year as is to be expected due to the global fossil fuel Cot release. A significant seasonal variation is not detectable in the "C record. The AI4C activity of the atmospheric C 0 2 samples is constantly lower by- 1 I f 2%, if compared to the northern hemisphere clean air level. The opposite effect should be expected from an observed C 0 2 concentration difference of about 3 4 ppm between the two hemispheres if due to I4C free fossil fuel CO,. A total (supposedly regional) AI4C depletion of about-20%, to-2S%,, compared to low latitudes in the southern hemisphere, can be attributed to exchange of atmospheric C 0 2 with low I4C surface water (AI4C =- loo%,) 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. 1