Measurements and trend analysis of O2, CO2 and δ13C of CO2 from the high altitude research station Junfgraujoch, Switzerland — A comparison with the observations from the remote site Puy de Dôme, France

Atmospheric O2 and CO2 flask measurements from the high altitude research station Jungfraujoch, Switzerland, and from the observatory at Puy de Dôme, France, are presented. Additionally, the Jungfraujoch δ13C record of CO2 is discussed. The observations on flask samples collected at the Jungfraujoch station show, since 2003, an enhancement of the oxygen trend which amounts to about 45 per meg/year with a corresponding CO2 increase of around 2.4 ppm/year. This enhancement is comparable with that observed at the Puy de Dôme station where oxygen, since mid 2002, has decreased with a rate of about 50 per meg/year whilst the CO2 increase was of around 1.7 ppm/year but exhibiting a higher variability. Several processes influence δO2/N2. However, these processes are marked with different oxidation ratios (O2:CO2) that can be used to distinguish them. The apparent slopes calculated from correlation plots between de-trended CO2 and δO2/N2 records as well as between corresponding trends are significantly larger than the observed terrestrial exchange and fossil fuel emission slopes indicating a strong oceanic influence. Since ocean–atmosphere exchange can have very variable O2:CO2 ratios depending on processes within the ocean, it is to our understanding the only possibility to explain our observations. The stability of the δO2/N2 scale is critical in this regard, therefore, it is addressed here and we found no significant scale drift which would influence our trend calculations. In our view more important are criterions on the data selection before trend analysis.