German Title: Untersuchung von atmosphärischem Kohlenmonoxid und Methan

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Abstract

The analysis of isotope ratios is widely used for the investigation of atmospheric trace gases. We measured the stable isotopes d13C and dD of atmospheric CH4 as well as d13C, d18O and the 14CO concentrations of atmospheric CO at Izana, Tenerife, from 1996 to 1999. We report the first directly measured dD seasonality for atmospheric background CH4. The large seasonal cycles in mixing and isotopic ratios of CH4 and CO enable inferences about the underlying source and sink processes. The large synoptic scale variations occurring for these trace gases at Izana made it possible to study source regions such as North America, Europe, as well as background conditions over the North Atlantic and Africa. We also measured d13C and dD on firn air samples from two Antarctic sites. From these measurements the atmospheric trends of d13C and dD of CH4 over the past fifty years have been reconstructed with the help of a firn air diffusion model. We find that parallel to increasing CH4 mixing ratios d13C increases, which is evidence for a growing contribution of the heavier anthropogenic CH4 sources. For dD we find a period of decline previous to 1975, followed by a gradual increase. This dD minimum is due to the non-equilibrium state between CH4 and its sources and sinks and has for the first time been detected for dD.

Translation of abstract (English)

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