Slocum glider data from Units 345 ("Cabot"), 490 ("Fortyniner"), 397 ("Nelson") and 399 ("Rayleigh") in the Celtic Sea during the Shelf Sea Biogeochemistry Project, 2014-2015.

The Shelf Sea Biogeochemistry Project (SSB) was a 5-year project (2014 to 2019) that aimed to deliver an improved understanding of key physical-biogeochemical interactions over a range of shelf sea environments and across successive seasons. From November 2014 to August 2015, four autonomous underwater gliders (Units 345, 419, 397 and 399) were deployed in the Celtic Sea to do repeat transects from the inner shelf (Central Celtic Sea/CANDYFLOSS station) to the shelf break (Celtic Sea 2 site near the shelf break). Each glider carried a CTD packet to measure temperature and conductivity, an Aanderra oxygen optode, and a WetLabs Triplet Eco puck to measure CDOM, chlorophyll and water-column backscatter. In total, the gliders collected over 17998 profiles over a combined distance of 5941 km. The gliders captured the seasonal transition from well-mixed to stratified water column (Unit 345), including the onset of seasonal stratification (Unit 419), the spring phytoplankton bloom (Unit 399), and the highly stratified summer conditions with a pronounced sub-surface chlorophyll maximum (Unit 399). Across the 9-month deployment, and in conjunction with the SSB project, these gliders provided key insights into the physical and biogeochemical variability of the Celtic Sea region across seasonal timescales.