Chemistry and the Environment, Short talk
EV-014

A decade of atmospheric CO2 mole fraction and stable isotope ratios at Jungfraujoch measured by QCLAS, GC-FID and IRMS

S. M. Pieber1, B. Tuzson1, S. Henne1, U. Karstens2, H. Moossen3, A. Jordan3, M. Rothe3, D. Brunner1, M. Steinbacher1, L. Emmenegger1*
1Air Pollution / Environmental Technology, Empa, Dübendorf, Switzerland, 2ICOS Carbon Portal, Lund University, Sweden, 3Max Planck Institute for Biogeochemistry, Jena, Germany

Long-term monitoring of the atmospheric carbon dioxide mole fractions (CO2) in pristine environments provides representative information on its long-term variability and rate of change. Such records are essential to understand the natural carbon cycle and the impact of anthropogenic activities. Stable isotope ratios (δ13C-CO2 and δ18O-CO2) provide additional constraints in models describing the source-sink processes in the carbon cycle, such as partitioning of CO2 between the different environmental reservoirs through physical, chemical and biochemical reactions: atmosphere, biosphere and ocean systems. Furthermore, evaluating atmospheric transport simulations against highly time-resolved observations helps refining bottom-up estimates of anthropogenic greenhouse gas fluxes and identifying gaps in our understanding of regional and category-specific contributions. This insight is critical in the efforts to monitor and mitigate anthropogenic impact on the environment. Key pre-requisites of long-term atmospheric observations are, however, high analytical precision, reliable operation resulting in adequate data coverage, and consistency among various monitoring sites and measurement techniques.

Here, we present a unique observational data set of atmospheric CO2, δ13C-CO2 and δ18O-CO2 for a nine year period (2009-2017) obtained at the high altitude research station Jungfraujoch, located in the Swiss Alps at 3580 m above sea level. The station contributes to Swiss, European and global monitoring programs and was labelled as a class 1 station within the European Integrated Carbon Observing System (ICOS) in 2018. The atmospheric CO2, δ13C-CO2 and δ18O-CO2 measurements are performed with two different analytical techniques and independent sampling strategies. High-resolution in-situ data are obtained continuously using a quantum cascade laser absorption spectrometer (QCLAS) [1-4]. Further, discrete air samples are collected as snapshots bi-weekly in form of triplicates in 1L glass flasks. The samples are subsequently analyzed off-line with gas chromatography and flame ionization detection (GC-FID) and isotope ratio mass spectrometry (IRMS) [5-6]. For interpretation and evaluation, we use receptor-oriented transport model simulations for CO2 mole fraction and δ13C-CO2 as described in [7] and references therein.

The comparison of the two independent sampling and measurement systems yielded good agreement and allowed determining decadal trends and seasonal profiles at Jungfraujoch under unpolluted free troposphere conditions. The high-resolution in-situ observations by QCLAS enhance our understanding of European CO2 sources and sinks by capturing hourly and diurnal variations and the shorter term dynamics of atmospheric CO2. Together with the transport simulations they allow to interpret the observed mole fractions when Jungfraujoch is influenced by air masses from the planetary boundary layer.

[1] Tuzson B, et al, 2008, APB, 92, 451;
[2] Nelson, DD, et al, 2008, APB, 90, 301;
[3] Tuzson B, et al, 2011, ACP, 11, 1685;
[4] Sturm P, et al, 2013, AMT, 6, 1659;
[5] Van Der Laan-Luijkx, IT, et al., 2013, AMT, 6, 1805;
[6] Ghosh, P, et al, 2005, RCMS, 19, 1097;
[7] Pieber SM, et al, 2020,
online at: https://presentations.copernicus.org/EGU2020/EGU2020-10588_presentation.pdf