Celtic Sea

Vertical spatial coordinates; Date and time; Salinity of the water column; Temperature of the water column; Chlorophyll pigment concentrations in water bodies; Horizontal spatial co-ordinates

Fluorometers; salinity sensor; water pressure sensors; water temperature sensor

An iRobot Seaglider (Serial Number 534) 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 4th and 25th April 2015. It maintained a position within 10 km of 49° 24.3’ N, 8° 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°C 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-a 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 UK Natural Environment Research Council (NERC) Shelf Sea Biogeochemistry Programme cruise (DY029). The processed data are held at BODC in Matlab format.

British Oceanographic Data Centre
Joseph Proudman Building 6 Brownlow Street
Liverpool
Merseyside
L3 5DA
United Kingdom