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SNAPO-CO2 data-set : A synthesis of total alkalinity and total dissolved inorganic carbon observations in the global ocean (1993-2022)
Since 2004, the Service facility SNAPO-CO2 (Service National d’Analyse des Paramètres Océaniques du CO2) housed by the LOCEAN laboratory (Paris, France) has been in charge for the analysis of Total Alkalinity (AT) and Total dissolved inorganic carbon (CT) of seawater samples on a series of cruises or ships of opportunity conducted in different regions in the frame of French projects. More than 44000 observations are synthetized in this work. Sampling was performed either from CTD-Rosette casts (Niskin bottles) or collected from the ship’s seawater supply (intake at about 5m depth). After completion of each cruise, discrete samples were returned back at LOCEAN laboratory and stored in a dark room at 4 °C before analysis generally within 2-3 months after sampling (sometimes within a week). AT and CT were analyzed simultaneously by potentiometric titration using a closed cell (Edmond, 1970). Certified Reference Materials (CRMs) provided by Pr. A. Dickson (Scripps Institution of Oceanography, San Diego, USA) were used to calibrate the measurements. The same instrumentation was used for underway measurements during OISO cruises (https://doi.org/10.18142/228) and OISO AT-CT data for 1998-2018 in the South Indian Ocean added in this synthesis.
The synthesis is organized in two files (one for Global ocean and the Coastal Zones, one for the Mediterranean Sea) with the same format:
Cruise name, Ship name, day, month, year, hour, minute, second, latitude, longitude, depth, AT (µmol/kg), Flag-AT, CT (µmol/kg), Flag-CT, Temperature (°C), Flag-Temp, Salinity (PSU), Flag-Salinity, nsample/cruise, nsample on file, sampling method.
Chemical oceanography, Physical oceanography
Ocean, total alkalinity, total dissolved inorganic carbon, temperature, salinity
79N, -73S, 180E, -180W
For each seawater sample, AT and CT were analyzed simultaneously by potentiometric titration using a closed cell (Edmond, 1970); concentrations calculated following Dickson et al (2007). https://doi.org/10.1016/0011-7471(70)90038-0
Edmond, J. M.: High precision determination of titration alkalinity and total carbon dioxide content of sea water by potentiometric titration, Deep-Sea Res., 17, 737–750, https://doi.org/10.1016/0011-7471(70)90038-0, 1970.
Dickson, A.G., Sabine, C.L., Christian, J.R.: Guide to Best Practices for Ocean CO2 Measurements. PICES Special, Publication 3, p. 191, 2007. https://www.ncei.noaa.gov/access/ocean-carbon-acidification-data-system/oceans/Handbook_2007.html