Long-term, full depth observations of horizontal velocities spanning 17 months, collected in a temperate shelf sea (Celtic Sea) on the NW European Shelf.

Five consecutive deployments of an upward looking, narrowband 150 kHz FlowQuest Acoustic Current Profiler (ACP), mounted on a bedframe, recorded full depth observations of horizontal velocities [m/s] spanning 17 months (March 2014 -July 2015). The sampling location was at the centre of the Celtic Sea, at a nominal location of 49.4 N, -8.6 E, in a nominal water depth of 145 metres. During each deployment, an alongside Sea-Bird Electronics (SBE) 16plus SeaCAT CTD recorded pressure. All observations presented here were collected as part of the UK Shelf Sea Biogeochemistry programme. The aim of these observations was to observe the transition of velocity structure throughout a typical seasonal cycle in a temperate continental shelf sea. A battery failure within the first deployment resulted in loss of data from May 6^th 2014 09:35 onwards. Observations resumed when the 2^nd bedframe was deployed in June 2014. The data were collected as part of the SSB research programme in the CaNDyFloSS: Carbon and Nutrient Dynamics and Fluxes over Shelf Systems research programme component. SSB was co-funded by the 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.