Assessing local CO2 contamination revealed by two near-by high altitude records at Jungfraujoch, Switzerland

Remote research stations are guarantor of high-quality atmospheric measurements as they are essentially exposed to pristine air masses. However, in a context of increasing touristic pressure for certain sites, attention should be paid to the local anthropogenic emission related to the infrastructure itself. Among emissions, carbon dioxide (CO2) is the most important anthropogenic greenhouse gas and a major contributor to the current global warming. Here, we compared two years of CO2 dry air mole fraction records from Jungfraujoch (Swiss Alps) measured at the Sphinx Laboratory (3580 m a.s.l.; JFJ) and the East Ridge facility (3705 m a.s.l.; JER; horizontal distance of similar to 1 km), respectively. Both stations show an overall increase of the annual mean CO2 mole fraction in line with current global trends. On a daily basis, values during the night (00h00-06h00) show robust coherence with variability ranging within the measurement uncertainties matching the WMO compatibility goal of 0.1 ppm, which we considered to be background air CO2 mole fraction for Central and Western Europe. However, JFJ record shows superimposed short-term variability with diurnal CO2 spikes centered around noon. Whereas the variability occurring during time intervals ranging from days to weeks seem to be driven by inputs of air masses from the planetary boundary layer, we suppose that the super-imposed diurnal CO2 spikes occurring essentially in summer are explained by local emission sources related to the infrastructure (visitors, tourism, etc). Nevertheless, we cannot point to a single triggering cause for those spikes as it probably results from a combination of factors. In order to minimize these local emissions, smooth collaboration between all the involved stakeholders is required.