Using cavity ringdown spectroscopy for continuous monitoring of δ 13 C(CO 2 ) and ƒCO 2 in the surface ocean
2012; Wiley; Volume: 10; Issue: 10 Linguagem: Inglês
10.4319/lom.2012.10.752
ISSN1541-5856
AutoresMeike Becker, Nils Andersen, Björn Fiedler, Peer Fietzek, Arne Körtzinger, Tobias Steinhoff, Gernot Friedrichs,
Tópico(s)Atmospheric and Environmental Gas Dynamics
ResumoThe role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the flux strengths between the ocean and the atmosphere can be quantified by measuring the fugacity of CO 2 (ƒCO 2 ) as well as the dissolved inorganic carbon (DIC) concentration and its isotopic composition in surface seawater. In this work, the potential of continuous wave cavity ringdown spectroscopy ( cw ‐CRDS) for autonomous underway measurements of ƒCO 2 and the stable carbon isotope ratio of DIC [δ 13 C(DIC)] is explored. For the first time, by using a conventional air‐sea equilibrator setup, both quantities were continuously and simultaneously recorded during a field deployment on two research cruises following meridional transects across the Atlantic Ocean (Bremerhaven, Germany—Punta Arenas, Chile). Data are compared against reference measurements by an established underway CO 2 monitoring system and isotope ratio mass spectrometric analysis of individual water samples. Agreement within ΔƒCO 2 = 0.35 µatm for atmospheric and ΔƒCO 2 = 2.5 µatm and Δδ 13 C(DIC) = 0.33‰ for seawater measurements have been achieved. Whereas “calibration‐free” ƒCO 2 monitoring is feasible, the measurement of accurate isotope ratios relies on running reference standards on a daily basis. Overall, the installed CRDS/equilibrator system was shown to be capable of reliable online monitoring of ƒCO 2 , equilibrium δ 13 C(CO 2 ), δ 13 C(DIC), and p O 2 aboard moving research vessels, thus making possible corresponding measurements with high spatial and temporal resolution.
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