Nitrogen and oxygen isotopes of dissolved inorganic nitrate from CTD niskin depth profiles from cruises NP2017 and NP2018 in Kongsfjorden and Rijpfjorden (Svalbard) during July-August 2017 and July 2018, respectively.

Nitrogen and oxygen isotopes of nitrate in seawater samples are determined from samples collected onboard RV Lance in Kongsfjorden and Rijpfjorden (Svalbard) from 29th July 2017 to 5th August 2017 (NP2017) and from 13th July 2018 to 15th July 2018 (NP2018) as part of the Changing Arctic Ocean programme. Seawater samples were filtered inline from Niskin bottles and stored frozen until sample analysis on land. Samples were measured for δ15N_NO₃ and δ18O_NO₃ on a GasBench II coupled with a Delta V Advantage using the denitrifier method. International standards USGS 34 and IAEA N3 and a North Atlantic Deep Water internal standard were run alongside seawater samples for inter-comparability. Measurements of δ15N_NO₃ and δ18O_NO₃ were corrected to AIR and VSMOW and the reference standards. Reproducibility is 0.3 and 0.5‰ for δ15N_NO₃ and δ18O_NO₃ respectively.