Browsing by Author "Mikaloff-Fletcher, SE"

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    NIWA’s δ13C-CO2 measurement programme: twenty years of monitoring in New Zealand and Antarctica, including the performance assessment of an in-situ analyser at Baring Head
    (American Geophysical Union, 2018-12-13) Moss, RC; Brailsford, GW; Martin, R; Nankivell, C; Nicol, S; Trans, PP; Mikaloff-Fletcher, SE; Michel, S; Keeling, RF; Werczynski, S; Gorjan, P; Sperlich, P
    NIWA is monitoring atmospheric trace gas species at multiple locations in New Zealand and Antarctica. NIWA’s main monitoring sites include i) Baring Head (BHD), a coastal site at the Southern tip of New Zealand’s North Island, ii) Lauder (LAU), an inland site in the central South Island of New Zealand and iii) Arrival Heights (ARH), an observatory on Ross Island in McMurdo Sound in Antarctica. Stable carbon isotopes in atmospheric carbon dioxide (δ13C-CO2) are measured at all three sites and represent a tracer to constrain CO2 fluxes. NIWA’s δ13C-CO2 measurements started in 1997 at BHD and ARH, while it commenced in 2009 at LAU. At all three sites, air is sampled in flasks during specific meteorological conditions, i.e. during Southerly events at BHD to sample Southern Ocean background air, or during mid-afternoon at LAU when the atmospheric boundary layer is well mixed. All flasks are analysed for δ13C-CO2 at the main gaslab in Wellington, using the same Gas Chromatography coupled Isotope Ratio Mass Spectrometry (GC-IRMS) system, ensuring optimal internal data consistency. Our instrument comprises a purpose-built GC unit and a commercial IRMS (MAT 252, Thermo Fisher, Bremen, Germany). In the last 20 years, the δ13C-CO2 monitoring programme has generated 1,708 measurements, with about 1182 from BHD, 158 from ARH, 368 from LAU. BHD is also sampled for δ13C-CO2 analysis within the NOAA and the Scripps flask networks, providing continuous intercomparison time series. In collaboration with the Australian Nuclear Science and Technology Organisation (ANSTO), we monitor Radon at BHD since 2015. Radon indicates if the sampled air has been in contact with terrestrial air masses, highlighting the potential for contamination with CO2 from terrestrial sources, which would impact on δ13C-CO2 observations. We also collaborate with Thermo Fisher (Bremen, Germany) and deployed Delta Ray – an in-situ analyser for δ13C and δ18O in atmospheric CO2 – at BHD. We compare the Delta Ray time series of δ13C and δ18O to δ13C-CO2 measurements in co-located flask samples as well as to continuous CO2 mole fractions, Radon and meteorological data from BHD.