The data set comprises temperature and salinity hydrocasts collected across the North Atlantic Ocean between 1910 and 1990. The measurements were collected by nine North Atlantic Ocean Weather Ships (OWS): OWS Alpha (1954 – 1974); OWS Bravo (1928 – 1974); OWS Charlie (1910 – 1982); OWS Echo (1910 – 1979); OWS India (1957 – 1975); OWS Juliet (1950 – 1975); OWS Kilo (1949 – 1973); OWS Lima (1948 – 1990); OWS Mike (1948 – 1982). This data set also includes measurements collected close to the general positions prior to the stationing of the Weather ships for the OWS Bravo, Charlie and Echo stations. Data from OWS Alpha, Bravo, Echo, India, Juliett and Kilo have been taken from the US National Oceanographic Data Center (NODC) compilations whereas those from OWS Charlie, Lima and Mike have been constructed from both the US NODC and International Council for the Exploration of the Seas (ICES) data holdings. In addition a daily averaged data set for OWS Charlie is available for the period 1975 - 1985 (supplied by Syd Levitus). This data set was supplied to the British Oceanographic Data Centre (BODC) by ICES. Additional files and more recent data can be acquired from the ICES website.