Hydrographic and nutrient data from 1975-2020 on the Scotian Shelf, Northwest Atlantic

Subsurface nutrients on the Scotian Shelf, an ocean region at the convergence of the subpolar and subtropical western boundary currents (i.e., Labrador Current and Gulf Stream), are chiefly modulated by upstream shelf and slope waters. Yet little is known about long-term fluctuations in the advective transport of nutrients to the shelf. To examine the relationships between subsurface nutrient concentrations and dominant slope water masses at the Scotian Shelf break, we assembled all available hydrographic data (temperature, salinity) and dissolved nutrient data (nitrate, phosphate, silicate) for the period 1975-2020. Hydrographic and nutrient data were extracted from the Fisheries and Oceans Canada (DFO) data archives MEDS (Marine Environmental Data Section Archive; DFO, 2023a) and BioChem (DFO, 2023b; Devine et al., 2014), respectively, and predominantly include data from current DFO programs (e.g., Atlantic Zone Monitoring Program (AZMP)) and legacy datasets. Hydrographic data consist of vertical water column profiles collected using a conductivity-temperature-depth (CTD) profiler, generally mounted to a rosette sampler equipped with Niskin bottles for discrete water and nutrient sampling (Mitchel et al., 2002). Nutrient (nitrate, phosphate, silicate) measurements generally followed well established colorimetric techniques outlined in detail in the AZMP sampling protocol (Mitchell et al., 2002). Only nutrient data that passed initial quality control (i.e., BioChem quality flags of 1 and 0) are included in the datasets provided here (see Devine et al., 2014 for details on quality control (QC) procedures). In addition to hydrographic and nutrient parameters, datasets further include information on designated regions (e.g., WSS: Western Scotian Shelf, CSS: Central Scotian Shelf, ESS: Eastern Scotian Shelf) as defined in Lehmann et al (2023).