A 5-year Validated Nitrate Dataset from the Ocean Observatories Initiative Pioneer - New England Shelf Array

The Ocean Observatories Initiative (OOI) deployed both the In-Situ Ultraviolet Spectrophotometer (ISUS) and Submersible Underwater Nitrate Sensor (SUNA) for continuous, in-situ measurement of nitrate. At the Pioneer-New England Shelf Array (Pioneer-NES), ISUS/SUNA sensors were deployed at 7-meters depth at the Inshore (ISSM), Central (CNSM), and Offshore (OSSM) Surface Mooring locations. The SUNA sensor replaced the ISUS sensors spring 2018. The SUNA was a major improvement in technology, with significant improvements in accuracy and precision. However, it still suffers from calibration drift due to lamp fatigue and biofouling as well as spectral interference due to bromide and fluorometric CDOM. Drift is corrected by application of post-cruise calibrations to recalculate the temperature-and-salinity corrected nitrate concentration following Sakamoto (2009a) and estimating a linear drift between pre-and-post cruise deployments. Validation is performed by comparison with discrete water samples collected during deployment/recovery of the sensors. These datasets include the nitrate data from the Pioneer-NES ISSM (CP03ISSM-RID26-07-NUTNRB000.nc), CNSM (CP01CNSM-RID26-07-NUTNRB000.nc), and OSSM (CP04OSSM-RID26-07-NUTNRB000.nc) SUNA instruments spanning Spring 2018 through Fall 2022. Each dataset contains the measured nitrate, the temperature-salinity corrected nitrate, the drift-corrected nitrate, and the nitrate following validation with bottle samples.