Atmospheric CO2 and δ13C Measurements from 2012 to 2014 at the Environmental Research Station Schneefernerhaus, Germany: Technical Corrections, Temporal Variations and Trajectory Clustering

Homa Ghasemifard,Ludwig Ries,Marvin Luepke,Michael Leuchner,Christian Schunk,Jia Chen,Ye Yuan,Annette Menzel

doi:10.4209/aaqr.2018.01.0010

Abstract

ABSTRACT This study presents continuous atmospheric CO2 and δ13C measurements by wavelength-scanned cavity ring down spectroscopy (Picarro G1101-i) at the high-mountain station Schneefernerhaus, Germany. δ13C values were post-corrected for methane and water spectral interferences using accompanying measurements of CH4 and H2O, and CO2 in dried air, respectively. The best precision of ±0.2‰ for δ13C and of ±4 ppb for CO2 was obtained with an integration time of about 1 hour for δ13C and 2 hours for CO2. The seasonality of CO2 and δ13C was studied by fitting background curves for a complete 2-year period. Peak-to-peak amplitudes of the averaged seasonal cycle were 15.5 ± 0.15 ppm for CO2 and 1.97 ± 0.53‰ for δ13C, respectively. Based on the HYSPLIT Model, air masses were classified into five clusters, with westerly and northeasterly flows being the most and the least frequent, respectively. In the wintertime, northwest and northeast clusters had a higher median level for ΔCO2 and a lower median level for Δδ13C (the difference between observed and background concentrations), likely caused by anthropogenic emissions. In the summertime, air masses from the northwest had the lowest ΔCO2 and the highest Δδ13C. Potential source contribution functions (PSCFs) were used to identify the potential source and sink areas. In winter, source areas for high CO2 mixing ratios (> 75th percentile) were mainly located in northwestern Europe. In summer, areas with high δ13C ratios (> 75th percentile), indicating a carbon sink, were observed in the air from Eastern and Central Poland.

Highlights

The sources and sinks of atmospheric carbon dioxide (CO2) play a critical role in governing global climate
This study presents continuous atmospheric CO2 and δ13C measurements by wavelength-scanned cavity ring down spectroscopy (Picarro G1101-i) at the high-mountain station Schneefernerhaus, Germany. δ13C values were post-corrected for methane and water spectral interferences using accompanying measurements of CH4 and H2O, and CO2 in dried air, respectively
CO2 mixing ratios simultaneously increase as δ13C values decrease, which is associated with seasonal vegetation activity

Summary

Introduction

The sources and sinks of atmospheric carbon dioxide (CO2) play a critical role in governing global climate. Especially fossil fuel combustion, cement manufacturing and land use changes trigger anthropogenic emissions and contribute to a steady increase of the atmospheric CO2 mixing ratio (IPCC, 2014; WMO, 2016; Xu et al, 2017). Half of the emitted CO2 is taken up by both the terrestrial biosphere and absorption in the ocean. The stable carbon isotope composition of CO2 (δ13C) allows distinguishing the exchange of fossil carbon from the atmosphere and surface reservoir fluxes (Keeling et al, 2011). Most plants of the terrestrial biosphere prefer to take up the light isotopologue 12CO2 and discriminate against 13CO2 (~18‰) (Farquhar et al, 1989). Since the discrimination by oceans is small, the carbon

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Conclusion