This dataset comprises images, geochemical composition, isotopic ratio, and X-ray diffraction (XRD) data from samples of Fe-oxyhydroxide (FeOOH) and seafloor massive sulphide (SMS) collected during the RRS James Cook cruise JC224 (March - April 2022) to the 13°30' N ocean core complex (OCC) region of the Mid-Atlantic Ridge, also known as the Semenov Hydrothermal Field. A total of 23 Robotic Underwater Vehicle (RUV) dives were completed with the HyBIS RUV (Murton et al., 2012) in addition to 6 rock dredges setup with a chain bag dredge and a steel bucket dredge behind it. Sampling was focused on the previously described massive sulphide-hosting areas: Semenov-1, -2, -4 and -5 (Escartin et al., 2017), as well as one dedicated dive to a near-circular feature protruding on the southern slope of the OCC - termed the "bulge". Analysis of the 42 FeOOH and SMS samples occurred onshore at the National Oceanography Centre (NOC) and the University of Southampton and the samples are held for long-term storage at NOC Southampton and Cardiff University. A range of analytical methods were used to collect the data, including: inductively-coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), and reflective light microphotography. The key aims of these analyses were: (1) to improve understanding regarding the formation of Fe-oxyhydroxide samples at SMS systems, and (2) to determine the potential of Fe-oxyhydroxide as an additional resource at SMS systems. The data were collected as part of a PhD project funded under the Natural Environment Research Council (NERC) project Ultramafic-hosted mineral Resource Assessment (ULTRA) grant, NE/S004068/1. This collection consists only of the data collected under the PhD project and not all data associated with the ULTRA project.

This dataset consists of measurements of 224Ra and macronutrients in core top water, porewaters and sediments, as well as calculated 224Ra and macronutrient fluxes (via 224Ra/228Th disequilibrium) from benthic incubations of replicate mesocosms containing selected benthic macrofauna. The experiments were conducted at the Biodiversity Ecosystem Futures Facility (BEFF lab) at the National Oceanography Centre Southampton during 2022. Sediment was collected from Rame Mud, Plymouth, and benthic organisms were collected from Rame Mud and from Loch Linhe, Scotland. For each incubation, homogenised, sieved (500 µm) sediment was added to a mesocosm to 10 cm depth, overlain by approximately 15 cm (approx. 1.3 L) seawater (0.45 µm filtered, UV sterilised, salinity 33), and left to settle for 24 hours before conducting a full water exchange. After water exchange, 1 individual of either Paraleptopentacta elongata , Edwardsia claparedii, Turritellinella tricarinata, or Amphiura chiajei was weighed and morphological measurements were taken before being added to the mesocosm. 3 replicates containing 1 individual were run for each species, in addition to 3 replicate control mesocosms containing no macrofauna. All mesocosms were continually aerated and maintained in a temperature-controlled water bath for 10 days under a 12:12h on/off light cycle. On days 4 and 8, 2.5ml of a mixed Phaeodactylum tricornutum: Tetraselmis suecica phytoplankton culture was added to all mesocosms. For a subset of mesocosms (mesocosms 14 and 15 ), daily water column nutrient samples (10 ml, 0.2 µm filtered) were taken ~5 cm below the water surface and frozen at -20°C for subsequent analysis. Experiments 1 & 2 were set up in the same manner, except that in experiment 2 only one species was included, but at higher replication (8 replicate mesocosms containing 1 individual each of E. claparedii + 1 control mesocosm). Water samples for macronutrient concentrations were analysed using a QuAAtro 39 autoanalyser (Seal Analytical) and samples for Ra activity were analysed using a Radium Delayed Coincidence Counter (RaDeCC) system.The work was conducted to quantify the influence of different species and individuals of benthic macrofauna on benthic flux, using 224Ra as a naturally occurring tracer of sediment-seawater exchange. For further information, please see the associated research paper doi: 10.1002/lno.70033

This dataset comprises a variety of sediment core data from the Semenov Hydrothermal Field region of the Mid-Atlantic Ridge, collected during RRS James Cook cruises JC224 (March - April 2022) and JC254 (October - November 2023). A total of 29 gravity cores, 9 mega-cores, and 25 push cores were successfully recovered. Analysis of the sediment core samples was conducted at the British Ocean Sediment Core Research Facility (BOSCORF), where the cores are held for long term storage, and included: imaging, spectrometry, geophysical and geochemical measurements of sediment and porewaters, radiocarbon dating, and stable isotope analysis. The main coring equipment used during both cruises was a gravity corer to collect sediment cores of up to 3 m in length. For JC224, a mega-core, with a USBL transponder attached to the frame, was used to obtain undisturbed cores from the upper 40 cm of the sediment surface. For JC254, push cores were also collected during several Remotely Operated Vehicle (ROV) dives using the Isis vehicle. The key objectives of the sediment coring were: (1) to reconstruct the history of the hydrothermal activity by dating plume fallout layers in the sedimentary record, and (2) to assess the role of the sediment cover in the preservation of seafloor massive sulphide (SMS) deposits in an ultra-slow spreading scenario. The data were collected as part of a PhD project funded under the Natural Environment Research Council (NERC) project Ultramafic-hosted mineral Resource Assessment (ULTRA) grant, NE/S004068/1. This collection consists only of the data collected under the PhD project and not all data associated with the ULTRA project.

The Rapid Climate Change (RAPID) data set comprises a diverse collection of oceanographic and benthic observations, including profiles of temperature, salinity, dissolved gases and currents. The dataset also includes discrete measurements of plankton, stable isotopes, dissolved metals, chlorofluorocarbons (CFCs) and nutrients in the water column, sediment grain size parameters and geochemistry, and atmospheric concentrations of inorganic halogens. The RAPID data were collected from numerous locations in the North Atlantic, North Sea, Greenland and Europe via over 30 cruises between 2004 and 2008. Many of the oceanographic data resulted from an extensive mooring array in the North Atlantic devoted to monitoring the Atlantic overturning circulation. These mooring arrays are continuing to return data in the follow-on programmes, Rapid Climate Change - Will the Atlantic Thermohaline Circulation Halt? (RAPID-WATCH, 2008-2015) and RAPID - Atlantic Meridional Overturning Circulation (RAPID-AMOC, 2015 onwards) which will result in a decadal time series spanning the North Atlantic. RAPID, RAPID-WATCH and RAPID-AMOC aim to investigate and understand the causes of rapid climate change, with a primary (but not exclusive) focus on the role of the Atlantic Ocean thermohaline circulation. A Rapid Climate Change project office has been established at the National Oceanography Centre, Southampton. The cruise and mooring data are managed by the British Oceanographic Data Centre and are supplemented by atmospheric model output held at the British Atmospheric Data Centre (BADC).

The dataset comprises physical, biogeochemical and biological oceanographic, surface meteorological and benthic measurements. Hydrographic profiles including temperature, salinity, fluorescence, transmissance and suspended sediment concentration were collected at numerous stations, while surface hydrographic (fluorescence, transmissance, sea surface temperature, salinity) and meteorological (irradiance, air temperature, humidity, wind speed/direction) data were collected across the survey areas. Sediment, pore water and water column samples were also collected for biogeochemical analysis, as were biological samples for the purposes of species classification and abundance analyses. The data were collected across the Indian Ocean, Arabian Sea and Pakistan margin areas between March and October 2003. Data collection was undertaken by the RRS Charles Darwin during four cruises: CD145 (12 March 2003 to 9 April 2003), CD146 (12 April 2003 to 30 May 2003), CD150 (22 August 2003 to 15 September 2003) and CD151 (17 September 2003 to 20 October 2003). Conductivity-temperature-depth (CTD) profilers with auxiliary sensors, benthic samplers and nets were deployed from the ship, while underway sensors provided continuous surface ocean, meteorological and bathymetric data. The study was designed to investigate an oxygen-minimum zone (OMZ) in the northern Arabian Sea. Chief Investigators include Gregory L Cowie (University of Edinburgh School of GeoSciences) and Brian J Bett (Southampton Oceanography Centre), while other institutions including the Dunstaffnage Marine Laboratory, University of Liverpool and Netherlands Institute of Ecology were also involved in the research. Data management is being undertaken by BODC. Some of the data are still undergoing processing at BODC and further data are expected from originators in the future.

The data set includes hydrographic profiles (including temperature, salinity, attenuance, chlorophyll, oxygen, irradiance, turbulence, sound velocity and currents), hydrographic time series (temperature, currents, fluorescence, bottom pressure), water samples (>70 parameters measured), sediment samples (>160 parameters measured), sediment trap samples (>10 parameters measured), production experiments and marine snow camera profiles. Additional meteorological and wave records are also available, as well as satellite imagery and underwater photography (water column and seabed). The data were collected on the Hebridean Slope (NW of Ireland) between March 1995 and September 1996. Measurements were collected via a combination of shipboard instrument deployments, including >1,800 conductivity-temperature-depth (CTD) and SeaSoar (undulating oceanographic recorder) profiles, >100 expendable bathythermograph (XBT) profiles, >38,000 acoustic Doppler current profiler (ADCP) profiles, >35 core profiles, >800 turbulence profiles, >40 marine snow camera profiles, >55 radiometer profiles and >25 sound velocity and travel time experiments. Benthic lander deployments were also undertaken, along with shipboard incubation experiments and drifting buoy deployments (48 tracks). An intensive water sampling programme provided >2,500 samples for biological and biogeochemical analysis. An extensive moored instrument array was maintained throughout the experiment, including sediment traps, recording current meters (104 series), electromagnetic current meters (9 series), ADCPs (16 series), thermistor chain and temperature probes (70 series), fluorometers (18 series), transmissometers (16 series), light meter (5 series), bottom pressure recorders (11 series), plus one waverider buoy series and three meteorological buoy time series. The Shelf Edge Study (SES) was an intensive multidisciplinary experiment and formed part of the NERC Land Ocean Interaction Study. The British Oceanographic Data Centre (BODC) assembled over 95% of the data sets collected during SES into its project database system. Once basic quality control procedures had been completed the data set was published, complete with extensive data documentation, on CD-ROM.

The dataset comprises hydrographic data, including salinity, temperature, depth, dissolved oxygen, transmittance (for suspended sediment), chlorophyll, irradiance, and current velocities. Both oceanographic and benthic measurements of nutrients (nitrate, nitrite, silicate, phosphate and ammonium), phytoplankton and zooplankton abundance, dissolved and particulate trace metals, primary and bacterial production, sulphur compounds and halocarbons were collected, as well as atmospheric physical and chemical measurements. The data were collected in the North Sea between August 1988 and October 1990 over a series of 38 cruises on RRS Challenger. Oceanographic measurements were taken using hydrographic profilers, moored instruments and shipboard underway systems. Underway meteorological data were also collected in addition to a comprehensive atmospheric sampling programme. Both continuous and discrete water samples were collected, providing biogeochemical and biological data. These were supplemented by net hauls. Benthic processes were investigated with sediment cores taken on eight survey cruises at six sites of varied character, three being in the area of summer stratification. Water and benthic sample analyses were supplemented by results of seabed and shipboard incubation experiments. The North Sea Project evolved from a NERC review of shelf seas research, which identified the need for a concerted multidisciplinary study of circulation, transport and production. The Proudman Oceanographic Laboratory (POL), now the National Oceanography Centre (NOC) hosted the project. It involved over 200 scientists and support staff from the Natural Environment Research Council (NERC), the Ministry of Agriculture, Fisheries and Food (MAFF - now DEFRA) and other academic institutes. The data are held at the British Oceanographic Data Centre and are available on CD-ROM.

The data set comprises a diverse collection of physical, chemical and biological measurements, encompassing over 1000 parameters. There are data from over 1650 conductivity-temperature-depth (CTD)/rosette stations, over 300 core profiles, over 370 sediment trap samples and much, much more. Most of this effort was directed at the region of the east Atlantic margin between La Chapelle Bank and the Goban Spur (between France and Ireland). In addition, there were two secondary areas of interest: the Norwegian Shelf Break just off Tromso and the Iberian Margin, either off Vigo or in the vicinity of the Tagus estuary. Measurements were collected from April 1993 until the end of December 1995 during 55 research cruise legs. Data were collected using a variety of equipment and techniques, including expendable bathythermography (XBTs), CTDs and oceanographic undulators with auxiliary sensors. These hydrographic profiles were accompanied by net hauls, plankton recorder deployments, sediment cores and comprehensive water and air sampling programmes during which a wide variety of chemical and biological parameters were measured. The station data were supplemented by underway measurements of oceanographic and meteorological properties. Results from production and trace metal experiments are also included in the dataset, as are bathymetric data from the British Oceanographic Data Centre (BODC) GEBCO digital Atlas, air-sea flux measurements and data from moored instruments and benthic landers that were deployed for periods from a few weeks to a year. The dataset also includes imagery from satellites, water column and seabed photography, scanning electron micrographs and X-ray photographs. FORTRAN source code for biogeochemical models developed during OMEX I is also included. The aim of the project was to study biogeochemical processes at the shelf break and to quantify the fluxes of material between the shelf and the open ocean. OMEX I involved scientists from 30 institutions in 10 countries. BODC is assembling the data sets collected during OMEX I into its database system and the data are also available on CD-ROM.