The dataset comprises chlorophyll-a concentrations from water samples taken during RRS James Clark Ross cruise JR304, from 15/11/2014 - 17/12/2014. The cruise sailed from Punta Arenas, Chile, returning to Stanley, Falkland Islands. Samples were taken during transit to Signy Island (South Orkneys), and then up through the Scotia Sea to BAS survey sites P2 and P3 as well as near South Georgia and in the Western Core Box survey area to the north of the island of South Georgia. 112 samples were collected from the ship’s uncontaminated underway supply, with an intake at approximately 6 m depth, every two hours during transit periods. 103 samples were collected, using a rosette sampler, from the upper 1000m during CTD (conductivity, temperature and depth probe) deployments. Each 300ml sample was filtered through a 0.8μm pore size, 25mm diameter, MPF300 filter, rinsed with milliQ water, placed in an eppendorf tube and stored at -20°C for later analysis. Samples were extracted in 90 % acetone for 22-24 hours at 4°C and measured on a Trilogy Turner Designs 7200 lab fluorometer calibrated with a pure chlorophyll-a standard (Sigma, UK) and set up following the method of Welschmeyer (1994). Data have not been adjusted for blanks. The data set was from the annual Western Core Box Cruise run by British Antarctic Survey (BAS). Data were collected to support the PhD of Anna Belcher and provide seasonal context for the cruise in terms of the primary production in the surface ocean. Chlorophyll samples were taken by Jenny Thomas (BAS), Gabi Stowasser (BAS), Sophie Fielding(BAS), Vicky Peck (BAS), Jess Gardner (University of East Anglia and BAS), Cecilia Liszka (BAS), Manon Duret (National Oceanography Centre, NOC), Anna Belcher (NOC), Anna Mikis (Cardiff University) , Marianne Wootton (Sir Alistair Hardy Foundation for Ocean Science), Sebastien Floter (GEOMAR Kiel). Chlorophyll samples were analysed aboard the R.R.S. James Clark Ross by Manon Duret and Anna Belcher from NOC.