Long‐term record of atmospheric CO₂ and stable isotopic ratios at Waliguan Observatory: Seasonally averaged 1991–2002 source/sink signals, and a comparison of 1998–2002 record to the 11 selected sites in the Northern Hemisphere

Abstract

This paper investigates seasonally averaged atmospheric CO2 source or sink signals observed at Waliguan Baseline Observatory (WLG, 36°17′N, 100°54′E, 3816 m asl) in western China from 1991 to 2002. Both linear and geometric mean regressions as well as statistical significance test were performed between detrended CO2 and stable isotope monthly data by means of Keeling Model and Miller‐Tans Model. The estimated slope Δδ13C/ΔCO2 due to the seasonality in CO2 and δ13C is (−0.050 ± 0.004)‰ ppm−1, the mean source/sink isotopic signatures δs (i.e., δ13Cs and δ18Os) are (−26.159 ± 1.924)‰ and (−7.662 ± 2.113)‰, respectively, and the mean atmospheric δ13C discrimination δdis (i.e., δs minus δbg) where the δbg is the isotopic value of the background atmosphere was (−18.174 ± 1.959)‰ by the Keeling Model, in agreement with results from other continental background sites in the Northern Hemisphere. We suggest that exchange with terrestrial biosphere dominates the observed CO2, δ13C and δ18O seasonal cycles at WLG. In addition, atmospheric CO2 and δ13C data from 11 selected NH sites in the NOAA ESRL air sampling network from 1998 to 2002 were analyzed and compared to the WLG data for the same period to better address common and specific features observed in this region. The annual cycle amplitude differences, secular and seasonal Δδ13C/ΔCO2 discrepancies among sites will be useful to better understand carbon uptake and release especially on the Eurasian continent. The estimated δs during certain times at each specific site could possibly provide useful information on CO2 fluxes.

Implications for CO₂ emissions and sinks changes in western China during 1995–2008 from atmospheric CO₂ at Waliguan

“…Both CO 2 regional sources and sinks information observed at Waliguan represent a relatively large-scale area due to the high altitude and extensive topography within the region. Therefore, measurements from the site can provide essential information on sources and sinks within the Eurasian continent (Zhou et al, 2005(Zhou et al, , 2006. A detailed discussion of the site, measurements, and calibrations for the system has been addressed in previous studies (Wen et al, 1997;Zhou et al, 2003).…”

“…In China, the longest observational record of atmospheric CO 2 has been obtained from remote Waliguan since the 1990s (Zhou et al, 2003). Based on these data obtained in earlier years, the seasonality, secular trend, annual cycle, and inter-annual variability of atmospheric CO 2 have been presented and characterized (Zhou et al, 2003(Zhou et al, , 2005(Zhou et al, , 2006. For example, Zhou et al (2003) discussed the background characteristics after filtering the episodes by using a meteorology method.…”

Evaluation of in situ measurements of atmospheric carbon monoxide at Mount Waliguan, China

“…However, discreet air samples are still collected weekly for CO, CO2 and CH4 by the NOAA cooperative air sampling program (http://www.esrl.noaa.gov/gmd/ccgg/). Observations of these trace gases at WLG provide essential information on sources and sinks within the Eurasian continent because of its unique location (Zhou et al, 2005(Zhou et al, , 2006 …”

Observation of atmospheric CO₂ and CO at Shangri-La station: results from the only regional station located at southwestern China

“…In the past years, a lot of measurement campaigns or research programmes were also carried out in China (Wang et al, 2002;Gao et al, 2005;Zhou et al, 2006;Fu et al, 2009;Liu et al, 2009;Zhang et al, 2011). Most of them focussed on emissions from or concentrations in severely polluted areas.…”

“…The four WMO/GAW stations have in place in situ greenhouse gas measurement systems (for CO 2 , CH 4 , etc.) already for years and their observations have been thoroughly investigated along with associated data analysis, interpretation and publications (Zhou et al, 2004(Zhou et al, , 2006Yao et al, 2012;Fang et al, 2013;Zhang et al, 2013;Fang et al, 2014;Liu et al, 2014).…”