This dataset consists of measurements of underway meteorology, navigation and sea-surface hydrography collected aboard RRS James Cook cruise JC156, which ran between Southampton and Guadeloupe from 20 December 2017 to 01 February 2018. Navigation data were collected using an Applanix POSMV system and meteorology and sea-surface hydrography were collected using the NMF Surfmet system. Both systems were run through the duration of the cruise, excepting times for cleaning, entering and leaving port, and while alongside. This cruise formed the field component of NERC Discovery Science project 'FRidge: The impact of mid-Ocean Ridges on the Ocean's Iron Cycle'. The main objectives of the project were to: 1. Document the changes in iron supply, cycling and speciation along the diverse hydrothermal systems of the northern Mid-Atlantic Ridge. 2. Link observational science with state-of-the-art ocean modelling to assess the global influence of mid-ocean ridges on the ocean iron cycle and the sustenance of surface productivity. To deliver on these objectives, a research expedition to the Atlantic Ocean was carried out to measure trace metals, nutrients and ocean physics over and around the Mid-Atlantic Ridge. Ultimately, this will be able to address the broader question of how the amount of iron from mid-ocean ridges can influence phytoplankton growth in the open ocean. The Discovery Science project was composed of Standard Grant reference NE/N010396/1 as the lead grant with child grant NE/N009525/1. The lead grant ran from 04 September 2017 to 03 March 2020, and was led by Professor Maeve Lohan of University of Southampton, School of Ocean and Earth Sciences. The child grant ran from 01 August 2017 to 31 August 2020, and was led by Dr Alessandro Tagliabue. The data from this project will be a part of the UK contribution to the international GEOTRACES programme. Research takes place along the GEOTRACES International Section GA13. The underway discrete salinity samples data and the underway navigation, meteorology and sea-surface hydrography data have been received by BODC as raw files from the RRS James Cook, processed and quality controlled using in-house BODC procedures and are available online.