Concentrations and stable isotopic composition of particulate organic carbon and nitrogen from water column samples collected in the central Arctic Ocean in 2019/2020 during the MOSAiC campaign

Concentrations and stable isotopic composition of particulate organic carbon and nitrogen from CTD-rosette casts during the MOSAiC (PS122) drift expedition in the central Arctic Ocean (see Fong et al. 2024 for details). 2-10 L of water were filtered onto precombusted GF/F filters (nominal pore size 0.7 µm) and frozen at -20°C. All samples were freeze dried. Samples for measurements of δ13C values, %C and %N were acidified by contact with HCl fumes for 4 h in a vacuum-enclosed system to remove carbonates, while samples for N stable isotope analysis were analyzed raw. Samples were analyzed using a continuous flow isotope ratio mass spectrometer (Delta V Plus with a Conflo IV interface, Thermo Scientific) interfaced with an elemental analyser (EA Isolink, Thermo Scientific) at the Littoral, Environment and Societies Joint Research Unit stable isotope facility (CNRS - University of La Rochelle, France). Normalization was done using reference materials (USGS61 and USG63, US Geological Survey). A subset of 28 dried and acidified samples was analyzed at AWI for POC and PON concentrations only, using a using a CHNS-O elemental analyzer (Euro EA 3000, HEKAtech) with acetanilide as a calibration standard.