CTD profiles (chlorophyll, density, dissolved oxygen concentration, conductivity, optical backscatter, salinity, temperature, transmittance, pressure, down-welling PAR) collected during UK Shelf Sea Biogeochemistry cruise RRS Discovery DY034.

(1) National Oceanography Centre, Liverpool; (2) National Marine Facilities Sea Systems; (3) British Oceanographic Data Centre, Liverpool; (4) National Oceanography Centre, Southampton

This dataset contains in-situ sensor data from 35 CTD casts (downcast profiles and at upcast bottle firings) collected in the Celtic Sea. The measurements were collected during RRS Discovery cruise DY034 in August-September 2015, as part of the UK Shelf Sea Biogeochemistry research programme (SSB), in order to provide information on the water mass characteristics and water column structure across the Celtic Sea shelf. Measurements were carried out using stainless steel and titanium CTD units. The steel unit comprised a Sea-Bird Electronics (SBE) 9 plus underwater unit, an SBE 11 plus deck unit, a NOC-S stainless steel 24-way frame and 24 10 L OTE Water Samplers; all of which were mounted on a stainless steel 24-way CTD frame. Attached to the CTD were two SBE 3P temperature sensors, two SBE 4C conductivity sensors, one Paroscientific Digiquartz pressure sensor, one SBE 43 dissolved oxygen sensor, two Biospherical QCP Cosine PAR sensors, one WETLabs BBRTD light scattering sensor, one Benthos 916T altimeter one CTG Aquatracka MKIII fluorometer and one CTG Alphatracka MKII transmissometer. The titanium unit comprised a Sea-Bird Electronics (SBE) 9 plus underwater unit, an SBE 11 plus deck unit, a NOC-S titanium frame 24-way frame and 24 10 L OTE Water Samplers; all of which were mounted on a stainless steel 24-way CTD frame. Attached to the CTD were two SBE 3P temperature sensors, two SBE 4C conductivity sensors, one Paroscientific Digiquartz pressure sensor, one SBE 43 dissolved oxygen sensor, two CTD 2-pi Underwater PAR sensors, one WETLabs BBRTD light scattering sensor, one Benthos 916T altimeter one CTG Aquatracka MKIII fluorometer and one CTG Alphatracka MKII transmissometer. Raw data were initially extracted and processed using Seabird Data Processing Software. Modules DatCnv, WildEdit, Filter, AlignCTD, CellTM, Derive and BottleSum were all run. Custom Matlab routines were then used 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. Data were calibrated by comparison with independent samples (where available). Measurements at upcast bottle firings were also calibrated (when possible). The data were collected as part of the SSB research programme in the CaNDyFloSS: Carbon and Nutrient Dynamics and Fluxes over Shelf Systems (NE/K00185X/1) research programme component. SSB was co-funded by the Natural Environment Research Council (NERC) and the Department for Environment, Food and Rural Affairs (Defra). The programme took a holistic approach to the cycling of nutrients and carbon and the controls on primary and secondary production in UK and European shelf seas, to increase understanding of these processes and their role in wider biogeochemical cycles. The British Oceanographic Data Centre (BODC) created the metadata entry and is responsible for holding master copies of the data.