Nitrate isotope measurements from CTD niskin depth profiles from Changing Arctic Ocean cruise JR16006 in the Barents Sea during summer 2017.

Nitrate isotope samples were collected onboard the RRS James Clark Ross in the Barents Sea from 30/06/2017-08/08/2017 as part of the Changing Arctic Oceans project. Seawater samples were filtered inline from the Niskin bottles, and frozen at -20°C until analysis on land. Samples were measured for δ¹⁵N-NO3 and δ¹⁸O-NO3 of nitrate using the Denitrifier method and bacterial strain P. aureofaciens. Samples were corrected using international reference standards IAEA-N3 and USGS-34 and an internal standard of North Atlantic Deep Water was run with each batch to check for inter-run comparability. Final values were calculated using the correction scheme of Weigand et al., (2016) with reproducibility of 0.1 and 0.3‰ for δ¹⁵N-NO3 and δ¹⁸O respectively.