CTD or Conductivity Temperature Depth stations measure temperature, conductivity and depth of the water column at various depths from the surface to within 10m of the seafloor. A CTD is the oceanographic instrument used to determine the conductivity, temperature, and depth of the ocean. The CTD may be incorporated into an array of Niskin bottles referred to as a carousel or rosette. The sampling bottles close at predefined depths, triggered either manually or by a computer, and the water samples may subsequently be analysed further for biological and chemical parameters. CTD stations have been collected in the greater North Atlantic Ocean area and waters around Ireland. Some CTD stations have been collected in the Norwegian Sea and Caribbean Sea. CTD stations have been collected annually since 1999. CTDs are deployed from the Celtic Explorer research vessel via an engineer working a crane with a scientist in the scientific lab monitoring the observations and measurements as the device descends in the water column. CTD data is useful in monitoring health of the oceans. CTD data is mainly collected by the Oceanographic Services team within Ocean Science and Information Services (OSIS) of the Marine Institute (Ireland). CTD data is complete for each deployment observed.