Gridded temperature, salinity and chlorophyll-a fluorescence from a Seaglider deployed for 21 days in the Celtic Sea in April 2015 under the Sensors on Gliders programme.

An iRobot Seaglider carrying a Seabird CT Sail, Paine pressure sensor and Wetlabs ECO-puck was deployed in the Celtic Sea, Northwest European Shelf for 21 days between the 4^th and 25^th April 2015. It maintained a position within 10 km of 49 degrees 24.3'N, 8 degrees 32.9'W and completed 1547 profiles between the sea surface and 120 m water depth. Its mission was to observe the evolution of the water column structure and the accumulation of phytoplankton biomass during spring phytoplankton bloom. Following the extraction of raw data and application of manufacturer calibrations, thermal lag corrections were applied to the temperature following the methods of Garau et al. (2011) and drawing upon a flight model similar to that described by Frajka-Williams et al (2011). Unrealistically high and low values of salinity, derived after thermal inertia corrections, were removed. Further, salinity values within 40 m of the surface (where the vertical speed of the glider was typically unstable) that were greater than 3 standard deviations from the mean salinity within top 40 m were removed. Each salinity profile was smoothed with an 8 m running mean window. Four calibrated CTD casts taken within 1.6 km of the glider were used to calibrate the gliders temperature and salinity. Based on the mean temperature and salinity of water between 80 m and 105 m the glider CT sensors were found to be reading 0.0277 degC and 0.0024 psu too low. These constant offsets were corrected for. Chlorophyll-a fluorescence was derived based on the manufacturers calibrations and checked against a fluorometer on the CTD. There is evidence of quenching within the surface 30-40 m during the day which has not been removed or corrected for here. Temperature, salinity and chlorophyll-<i>a</i> fluorescence were gridded onto regular 1 m depth intervals and the profile average position and time calculated. The glider was funded by the NERC Sensors on Gliders Programme and deployed during a NERC Shelf Sea Biogeochemistry Programme cruise (DY029). The British Oceanographic Data Centre (BODC) created the metadata entry and is responsible for holding master copies of the data.<br>Frajka-Williams, E., C. C. Eriksen, P. B. Rhines and R. R. Harcourt. 2011. Determining Vertical Water Velocities from Seaglider. J. Atmos. Oceanic Technol. 28: 1641-1656. doi:10.1175/2011jtecho830.1.<br>Garau, B., S. Ruiz, W. F. G. Zhang, A. Pascual, E. Heslop, J. Kerfoot and J. Tintore. 2011. Thermal Lag Correction on Slocum CTD Glider Data. J. Atmos. Oceanic Technol. 28: 1065-1071. doi: 10.1175/jtech-d-10-05030.1.