The Carbon Uptake and Seasonal Traits in Antarctic Remineralisation Depth (CUSTARD) data set comprises hydrographic data, including measurements of temperature, salinity and currents, complemented by bathymetric, meteorological and nutrient data. All the observational data from the project were collected at, and south of, the Ocean Observatories Initiative (OOI) Global Southern Ocean Array, located south-west of Chile. Data collection activities span from November 2018 to January 2020 over 3 cruises (DY096, DY111 and DY112). The main aim of the CUSTARD project is to quantify the seasonal drivers of carbon fluxes in a region of the Southern Ocean upper limb, and estimate how long different quantities of carbon are kept out of the atmosphere based on the water flow routes at the observed remineralisation depths. The lead grant was funded by the NERC grant reference NE/P021247/1 with child grants NE/P021328/1, NE/P021336/1, NE/P021263/1. NE/P021247/1 was held at the National Oceanography Centre, led by Adrian Martin. Child grants were lead by Mark Moore of University of Southampton, Simon Ussher of University of Plymouth and Dorothee Bakker of University of East Anglia respectively.