RRS James Cook Cruise JC159 28 February - 11 April 2018. Hydrographic sections from the Brazil to the Benguela Current across 24S in the Atlantic

A Hydrographic section was occupied at a nominal latitude of 24°S in the Atlantic Ocean during March and April 2018 on Cruise JC159 of RRS James Cook. The primary objective of this cruise was to measure ocean physical, chemical and biological parameters in order to establish regional budgets of heat, freshwater and carbon, and to infer decadal variability. In addition, 371 Niskin Bottles were sampled for microplastics, reflecting increasing awareness of plastics pollution in the oceans. A total of 121 CTD/LADCP stations were conducted, including one test station and two CFC bottle blank stations. In addition to temperature, salinity and oxygen profiles from the sensors on the CTD package, water samples from a 24 x 20 litre rosette were analysed for the following parameters at all stations: salinity; dissolved oxygen; inorganic nutrients; alkalinity and dissolved inorganic carbon; CFCs. Samples were collected for shore analysis for oxygen and carbon isotopes (del-18O, del13C and del-14C). Samples were collected and filtered for pigments (shore analysis) at 44 stations and for microplastics at 45 stations. 8 Argo floats were deployed, including two Bio-PROVOR floats and 2 Deep ARVORs. In addition, samples were collected from the ships’ underway system to calibrate and compliment the data continually collected by the TSG (thermosalinograph). Full depth velocity measurements were made at every station by LADCP (Lowered Acoustic Doppler Current Profiler) mounted on the frame of the rosette. Throughout the cruise, velocity data in the upper few hundred metres of the water column were collected by the ship’s VMADCP (Vessel Mounted Acoustic Doppler Current Profiler) transducers (75Hz and 150Hz) mounted on one of the two drop keels. Meteorological variables were monitored using the onboard surface water and meteorological sampling system (SURFMET). Bathymetric data were collected using the Kongsberg EM122 multibeam system and the EA640 echo sounder. This report describes the methods used to acquire and process the data on board the ship during cruise JC159.