CTD data from NERC Changing Arctic Ocean Cruise JR17005 on the RRS James Clark Ross, May-June 2018.

This data set contains a total of 72 CTD casts that were completed from the RRS James Clark Ross (cruise number JR17005), between the 13th May 2018 and 6th June 2018. The cruise was part of the Changing Arctic Ocean Programme funded by the Natural Environment Research Council, UK (www.changing-arctic-ocean.ac.uk). Three main transects were completed. The first from the deep water of the Greenland Basin up into the Norsk Trough on the East Greenland shelf at a latitude of 76°N. A second transect was completed at 79°N across the Fram Strait, starting at 10°W on the East Greenland Shelf and finishing a few miles off the coast of Svalbard. A third transect was completed to the south of Svalbard within Storfjorden at 77°N. Raw data were initially extracted and processed using Seabird Data Processing Software (v7.26.7). Modules DatCnv, WildEdit, Filter, AlignCTD, CellTM, Derive and BottleSum were all run. Custom Matlab routines were then used to apply a deep oxygen hysteresis correction, to remove out of water and surface soak values, to filter anomalous data points and to average the profiles onto a 1 db pressure grid. Each 1 db averaged profile (downcast) contains the following variables: latitude, longitude, day number, pressure (db), depth (m), primary and secondary temperature (°C), conductivity (mS/cm), salinity (psu) and potential density (kg m^-3), chlorophyll-a fluorescence (mg m^-3), beam attenuation (1/m), beam transmission (%), photosynthetically active radiation (W m^-2), oxygen concentration (µmol/L) and altimetry (metres above the bottom). Files are also provided that contain 5 second averages of all the above variables around the times of bottle firings (on the up casts). The SBE43 oxygen sensor was calibrated against Winkler titration samples (taken in triplicate) from 20 L Niskin bottles mounted onto the frame. Salinity samples analysed on a Guildline Autosal instrument were used to calibrate the salinity profiles.