The data included in this repository includes the biogeochemical model output of nitrogen isotope fields. These data were generated by simulations with the NEMOv4.0 Ocean General Circulation Model, SI3 sea ice model, and Pelagic Interactions Scheme for Carbon and Ecosystem Studies version 2 (PISCESv2) biogeochemical model. Nitrogen isotopes were integrated within PISCESv2 for the purpoes of this study. All data here are in longitude, latitude and time cordinates. No depth coordinate is provided as all values are averaged over the upper 100 metres of the model. The file names mean the following: ETOPO - refers to how the curvilinear, native grid of the model was re-gridded to a regular 360x180 longitude-latitude grid uisng the etopo60 coordinate system. JRA55 - these are the reanalysis-driven simulations, for which we used the Japanese Atmospheric Reanalysis (JRA55do). future - these are the emissions-driven simulations (historical from 1850-2005, then according to Representative Concentration Pathway 8.5 from 2006-2100.) picontrol - these are parallel to the emissions-driven simulations but do not include the increase in emissions. ndep - refers to if the historical increase in anthropogenic nitrogen deposition was included in the simulation d15Nno3 - isotopic composition of nitrate averaged over the upper 100 metres d15Npom - isotopic composition of particulate organic matter averaged over the upper 100 metres predictors - the average values of salinity, N* and particulate organic matter over the upper 100 metres annualave - annual averages, so that the data are inter-annual 1970-1990ave_months - average monthy values over the period 1970-1990.