RRS James Clark Ross Cruise JR18002, 3-22 Nov 2018. Repeat hydrographic measurements on GO-SHIP line SR1b.

The 24th complete occupation of the Drake Passage section SR1b obtained full-depth temperature, salinity, dissolved oxygen, and lowered ADCP velocity profiles at 29 stations between Burdwood Bank and Elephant Island, along with water column samples of salinity, dissolved oxygen, nutrients, carbonate system parameters, oxygen and carbon isotopes, and CFCs and SF6, and underway surface ocean and meteorological data and vessel mounted current measurements. The aims of these decadal repeat hydrographic measurements are to monitor the Antarctic Circumpolar Current’s properties and transports and contribute to understanding the Southern Ocean’s role in heat and carbon storage and transports and the contribution of ocean circulation to regional patterns of warming and sea level rise. They contribute to the international Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) and were funded by NERC through the Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA) National Capability programme and Transient tracer-based Investigation of Circulation and Thermal Ocean Change (TICTOC) large grant. At approximately half the stations large-volume samples were taken to measure radium and actinium isotopes to constrain iron fluxes as part of the NERC-funded RaCE:TraX project. The cruise also included opportunistic measurements of water column microplastics (funded by the Collaborative Antarctic Science Scheme) and nutrient isotopes, and experiments on phytoplankton nutrient limitation.