The GEBCO_2021 Grid is a global continuous terrain model for ocean and land with a spatial resolution of 15 arc seconds. In regions outside of the Arctic Ocean area, the grid uses as a base, Version 2.2 of the SRTM15+ data set between latitudes of 50 degrees South and 60 degrees North. This data set is a fusion of land topography with measured and estimated seafloor topography. This version of SRTM15+ is similar to version 2.1 [Tozer et al., 2020] with minor updates. Version 2.2 uses predicted depths based on the V29 gravity model [Sandwell et al., 2019] and approximately 400 small areas containing suspect data were visually identified and removed from the grid. Included on top of this base grid are gridded bathymetric data sets developed by the four Regional Centers of The Nippon Foundation-GEBCO Seabed 2030 Project. The GEBCO_2021 Grid represents all data within the 2021 compilation. The compilation of the GEBCO_2021 Grid was carried out at the Seabed 2030 Global Center, hosted at the National Oceanography Centre, UK, with the aim of producing a seamless global terrain model. Outside of Polar regions, the gridded bathymetric data sets are supplied by the Regional Centers as sparse grids, i.e. only grid cells that contain data were populated, were included on to the base grid without any blending. The data sets supplied in the form of complete grids (primarily areas north of 60N and south of 50S) were included using feather blending techniques from GlobalMapper software. The primary GEBCO_2021 grid contains land and ice surface elevation information - as provided for previous GEBCO grid releases. In addition, for the 2021 release a version with under-ice topography/bathymetry information for Greenland and Antarctica is also available. The GEBCO_2021 Grid has been developed through the Nippon Foundation-GEBCO Seabed 2030 Project. This is a collaborative project between the Nippon Foundation of Japan and the General Bathymetric Chart of the Oceans (GEBCO). It aims to bring together all available bathymetric data to produce the definitive map of the world ocean floor by 2030 and make it available to all. Funded by the Nippon Foundation, the four Seabed 2030 Regional Centers include the Southern Ocean - hosted at the Alfred Wegener Institute, Germany; South and West Pacific Ocean - hosted at the National Institute of Water and Atmospheric Research, New Zealand; Atlantic and Indian Oceans - hosted at the Lamont Doherty Earth Observatory, Columbia University, USA; Arctic and North Pacific Oceans - hosted at Stockholm University, Sweden and the Center for Coastal and Ocean Mapping at the University of New Hampshire, USA.

Collection of geophysical and oceanographic data from several cruises dedicated to the repeated mapping and monitoring of three UK Marine Protected Areas (MPAs) - Haig Fras, Whittard Canyon and the Darwin Mounds. Data were collected during the following 2018-2020 cruises: JC166/7, DY103, DY108/9, DY120 and DY106. Data collection took place at three of the UK’s MPAs - Haig Fras Marine Conservation Zone (MCZ) in the Celtic Sea, Whittard Canyon submarine complex, which includes The Canyons MCZ, situated off the south west UK continental shelf and Darwin Mounds Special Area of Conservation (SAC), situated in the northern Rockall Trough. An Autonomous Underwater Vehicle (AUV) was used to collect photographic data, sidescan sonar and multibeam bathymetry. Other data included shipboard multibeam bathymetry data; moored ADCP, CTD and sediment trap datasets from repeat mooring deployments; ROV video, pushcores and specimen samples; settling plate experiments; box cores and mega cores; BioCam imagery. The MPAs under investigation had been previously surveyed on cruises JC035 (2009) and JC125 (2015) hence these cruises formed part of the Fixed Point Observations Underpinning Activity. Here repeated observations and surveys of MPAs and their surroundings aim to provide insight into the development and recovery of benthic ecosystems following natural and/or anthropogenic impacts. The data collection was undertaken by scientists at the UK’s National Oceanography Centre (NOC) and formed part of the Natural Environment Research Council (NERC) Climate Linked Atlantic Sector Science (CLASS) Programme (NERC grant reference NE/R015953/1).

Nitrogen Fixation was determined from samples collected during CTD profiles at the surface and chlorophyll maximum once per day from the North Atlantic at approximately 24.5 degrees North on cruise D346 between 5th January and 19th February 2010. The samples were incubated at sea-surface temperature for 24 hours, filtered onto ashed-GF/F's and dried in oven at 50 degrees for further 24 hours. The data are being used as part of a wider study in the role iron has in nitrogen fixation. David Honey collected these data as part of his PhD, supervised by Martha Gledhill and Eric Achterberg.

This dataset consists of measurements of underway meteorology, navigation and sea surface hydrography, seismic reflection and refraction, and bathythermograph data collected during a comprehensive survey of the Tonga-Kermadec island arc-deep-sea trench system, undertaken between April and June 2011. Data were collected on RV Sonne cruise SO215 by an integrated marine geophysical experiment that comprised simultaneous seismic reflection (MCS) and wide-angle (WA) refraction, gravity, magnetic, bathymetry and sub-seabed high-resolution imaging of the Louisville Ridge-Tonga-Kermadec Trench collision system. This cruise formed the field component of NERC Discovery Science project "The Louisville Ridge-Tonga Trench collision: Implications for subduction zone dynamics". The key scientific objectives for the cruise were as follows: a)Determine the 'background' crustal and uppermost mantle structure of the subducting plate; b)Determine the crustal and uppermost mantle structure across and along the Louisville Ridge; c)Determine the physical properties of the leading edges of the subducting and over-riding plates; d)Determine the state of isostasy, ridge-related flexure and moat characteristics at the Louisville Ridge, and the mechanical properties of the subducting and over-riding plates; e)Determine the seafloor morphology and collision-related deformation in the Tonga forearc. The Discovery Science project was composed of Standard Grant reference NE/F004273/1 as the lead grant with child grant NE/F005318/1. The lead grant ran from 1 Mar 2011 - 31 Aug 2016 and the child grant ran from 1 Oct 2010 - 30 Sep 2014. Professor Christine Peirce of University of Durham, Department of Earth Sciences was the principal investigator of the lead grant of this project. Prof Anthony Watts of University of Oxford, Earth Science was the principal investigator of the child grant. The bathythermograph data have been received by BODC as raw files from the RV Sonne, processed and quality controlled using in-house BODC procedures and will be made available online soon. The remaining data have been received by BODC as raw files from the RV Sonne and are available on request.

This dataset contains a variety of hydrographic measurements including temperature, salinity, sound velocity, current speed/ direction and seismic data. Hydrographic profilers provided measurements of temperature, salinity, sound velocity and density. Four mooring stations were also installed as part of this project, with three minilogger chains providing temperature data and four moored ADCPs measuring current veloicty. The project ran from February 2006 to September 2009, however all of the data were collected between 17 April 2007 and 14 May 2007 during two cruises which took place in the Gulf of Cadiz. The research was conducted using two research vessels, the RRS Discovery (cruise D318) and the RV Poseidon (cruise PO350). The RRS Discovery cruise D318 was split into two legs, D318a, which took place between 17 April 2007 and 23 April 2007 and D318b, which took place between 29 April 2007 and 14 May 2007. For the second leg of cruise D318, the RRS Discovery was joined by the RV Poseidon. Hydrographic measurements were taken using a variety of instruments, including expendable bathythermographs (XBT), expendable CTDs (XCTD), conductivity-temperature depth (CTD) profilers, acoustic doppler current profilers (ADCP) and VEMCO minilogger chains. Airguns and streamers were used in the recording of the seismic data. The main objectives of the Geophysical Oceanography (GO) project were A) To evaluate and improve new research methods in the developing field of seismic oceanography by exploiting the opportunity of two-ship operations between RSS Discovery and RV Poseidon and B) To study the internal wave field and mixing processes in the Gulf of Cadiz and demonstrate quantitative links between seismic and oceanographic measurements. The cruise was coordinated by Durham Univerity and funded under an EU grant as part of the Framework 6 NEST programme. Eight scientific institutions were involved in the project. These were: the University of Durham, the Proudman Oceanographic Laboratory (POL), the Helmholtz Centre for Ocean Research Kiel (IFM-GEOMAR), the French Research Institute for Exploitation of the Sea (IFREMER), the Italian National Agency for New Technologies, the Energy and Sustainable Economic Development (ENEA), the Spanish National Research Council (CSIC), the University of Western Brittany and the University of Lisbon. Data from the programme are held at the British Oceanographic Data Centre.

This dataset consists of measurements of density, electrical conductivity, sound velocity and travel time, salinity, depth and temperature of the water column. The data were acquired from the RV Falcon Spirit, the Plymouth University vessel. The small 14m catamaran was used on a daily basis from 13 May 2012 to 24 May 2012 in the Celtic Sea, off the Cornish coast, with the idea to capture high-quality, spatially-resolved field data ahead of the Wave Hub construction. Measurements were collected using CTDs, moored temperature loggers, ADCP, VMADCP and towed minibat CTD. These cruises formed the field component of NERC Discovery Science project "Wave Hub baseline study". The aims of the research were to obtain a detailed oceanographic study at the Wave Hub site and surrounds - covering the whole range of physical, chemical and biological parameters before the deployment of Wave Hub infrastructure and wave energy devices – and to ensure data acquisition in time and space to allow development of physical and ecosystem models at scales relevant to wave arrays. Ultimately models will make predictive assessments of the extent, timescales and intensity of ecosystem impacts and perturbation resulting from implementation of wave energy arrays. Other aims include: engagement of environmental economists to ensure the data can be used to develop economic valuation estimates of critical life-supporting ecosystem services at scales appropriate to arrays of wave devices for comparison with other uses of marine space and to address questions that have arisen directly in respect of marine renewable energy development and sustainable use of marine resources. The Discovery Science project was composed of Standard Grant reference NE/I015094/1 as the lead grant with child grants NE/I015183/1 and NE/I015108/1. The lead grant, NE/I015094/1, ran from 01 August 2010 to 31 July 2012, with Dr Ricardo Javier Torres, Plymouth Marine Laboratory, as principal investigator. The child grant NE/I015183/1 ran from 01 August 2010 to 31 July 2011, led by Professor Michael Richard Belmont, University of Exeter. The second child grant, NE/I015108/1, ran from 03 December 2010 to 31 July 2012, led by Dr Philip John Hosegood, University of Plymouth. All data detailed here were received by BODC as raw files from the RV Falcon, processed and quality controlled using in-house BODC procedures. Towed undulator CTD data and temperature logger data have been processed to completion and are available online on the BODC website. The remaining data will be made available in the near future.

Five ocean gliders were deployed during cruise SSD-024 as part of the Bay of Bengal Boundary Layer Experiment (BoBBLE), a collaborative project between India and the UK, funded jointly by Ministry of Earth Sciences (MoES), Government of India, and Natural Environmental Research Council, UK, through the “Drivers of Variability in the South Asian Monsoon” programme. The major objective of this project is to understand the east-west contrast in the upper layer characteristics of the southern Bay of Bengal and its interaction with the summer monsoon. The major observational objectives of SSD-024 were to profile the hydrography along 8°N in international waters and to carry out a 10-day time series at 8°N, 89°E. 14 scientists from India and 8 from the UK made up the scientific contingent of SSD-024. Five Seagliders were successfully deployed in the southern Bay of Bengal from ORV Sindhu Sadhana during the BoBBLE cruise. These autonomous underwater vehicles fly in a continuous repeating sawtooth pattern from the surface down to a maximum depth of 1000 m. They are all equipped with conductivity-temperature-depth (CTD) sensors. Additional sensors include dissolved oxygen, chlorophyll fluorescence and backscatter, photosynthetically active radiation (PAR) and microstructure sensors. Three Seagliders (including one microstructure enabled glider) are from the University of East Anglia (UEA), UK glider facility. The remaining two Seagliders are from the Marine Autonomous Robotics Systems (MARS) national UK facility. All five Seagliders were deployed and piloted by UEA and associated personnel.

The GEBCO_2020 Grid is a global continuous terrain model for ocean and land with a spatial resolution of 15 arc seconds. In regions outside of the Arctic Ocean area, the grid uses as a base Version 2 of the SRTM15_plus data set (Tozer, B. et al, 2019). This data set is a fusion of land topography with measured and estimated seafloor topography. Included on top of this base grid are gridded bathymetric data sets developed by the four Regional Centers of The Nippon Foundation-GEBCO Seabed 2030 Project. The GEBCO_2020 Grid represents all data within the 2020 compilation. The compilation of the GEBCO_2020 Grid was carried out at the Seabed 2030 Global Center, hosted at the National Oceanography Centre, UK, with the aim of producing a seamless global terrain model. Outside of Polar regions, the gridded bathymetric data sets supplied by the Regional Centers, as sparse grids, i.e. only grid cells that contain data were populated, were included on to the base grid without any blending. The data sets supplied in the form of complete grids (primarily areas north of 60N and south of 50S) were included using feather blending techniques from GlobalMapper software. The GEBCO_2020 Grid has been developed through the Nippon Foundation-GEBCO Seabed 2030 Project. This is a collaborative project between the Nippon Foundation of Japan and the General Bathymetric Chart of the Oceans (GEBCO). It aims to bring together all available bathymetric data to produce the definitive map of the world ocean floor by 2030 and make it available to all. Funded by the Nippon Foundation, the four Seabed 2030 Regional Centers include the Southern Ocean - hosted at the Alfred Wegener Institute, Germany; South and West Pacific Ocean - hosted at the National Institute of Water and Atmospheric Research, New Zealand; Atlantic and Indian Oceans - hosted at the Lamont Doherty Earth Observatory, Columbia University, USA; Arctic and North Pacific Oceans - hosted at Stockholm University, Sweden and the Center for Coastal and Ocean Mapping at the University of New Hampshire, USA.

This dataset consists of ~18000 scanned images (available to download in .jpg, but high resolution .tiff images are also available) from historical UK tide gauge ledgers. In 1993 the British Oceanographic Data Centre (BODC) acquired the registers from the Mersey Docks and Harbour Company (MDHC). These registers were in the form of large, leather‐bound volumes dating back to 1853 for Hilbre Island and 1857 for Georges Pier. The earlier books for Georges Pier and Hilbre Island contain 1/4 hourly heights and the remaining volumes mainly list high and low waters. Some of the ledgers include metrological data alongside the tidal information. There was also one ledger from the port of Sheerness. There were 142 books included in this project. The majority of the sites were in the Mersey Estuary, with one in the Thames Estuary. The sites are listed below, with the time period covered (gaps not shown): Dutton Locks Lower Gauge, River Weaver (53.28778,-2.62111) 1897-1917 Dutton Locks Upper Gauge, River Weaver (53.35111,-2.90694) 1897-1906 Eastham Lock, Mersey (53.3167,-2.9499) 1892-1981 Fiddlers Ferry (53.36667,-2.65) 1891-1974 Frodsham Bridge, River Weaver (53.30167,-2.70833) 1891-1917 Garston Dock, Mersey (53.40528,-2.99444) 1892-1917 George’s Pier, Liverpool (53.28333,-2.85) 1857-1912 Hale Head, Mersey (53.38333,-2.6) 1891-1917 Hilbre Island (53.3833,-3.2276) 1853-1987 Liverpool, Gladstone Dock (53.44969,-3.018) 1971-1981 Liverpool, Princes Pier (53.4083,-2.9983) 1971-1981 Stanlaw, Mersey (53.39556,-3.00833) 1891-1917 Sheerness (51.44564,0.74344) 1832-1849 Tranmere (53.3756,-2.9978) 1974-1981 Warrington, Mersey (53.28722,-2.6225) 1891-1912 Waterloo (53.4125,-3.0031) 1986-1987 Widnes, Mersey (53.32361,-2.79306) 1892-1917 Woodside Landing, Birkenhead (53.35,-2.73333) 1847-1897 The ledger scanning was put out to tender. Most of the ledgers were quite old and fragile, the books had to be preserved in their original format and binding and care had to be taken to prevent further deterioration as they were irreplaceable. It was specified in the tender that a specialist organisation was required with a proven track record of handling antique books. They had to use an archival quality overhead flatbed book scanner/ planetary scanner to preserve the pages and spines of the books. Some of the ledgers were quite large and required a scanner that could accommodate them without damage. The aim of this project was to digitise and scan historic analogue chart and manuscript sea level records held in the archive of the British Oceanographic Data Centre and to make these records available to the wider community. These data are unrepeatable scientific measurements and we want to encourage their reuse. Extending back and infilling tide gauge records will help with, among other things, climate change research, storm surge predictions and coastal land movement studies. BODC received a grant from the JISC eContent Capital Programme 2011-13, Strand B: Mass Digitisation to carry out the scanning of the ledgers.

Macrofauna and polychaete species abundance data were obtained from replicate megacore samples collected from inside the Whittard Canyon (N.E. Atlantic) and the adjacent slope to the west of the canyon during cruise JC036 in June and July 2009. Four sites were sampled, three in the Whittard Canyon branches (Western, Central and Eastern) and one site on the slope to the west of the canyon. Five deployments were conducted in the Western branch, six in the Central and Eastern branches and five at the slope site. One extra deployment was made in the Central and Eastern branches to compensate for the failure to recover sufficient cores. All sites were located at 3500 m depth. Samples were collected using a Megacorer fitted with eight large (100 mm internal diameter) core tubes. Core slices from the same sediment layer from one deployment were pooled to make one replicate sample. The number of cores pooled per deployment ranged from 3 to 7 and the area of seabed sampled varied accordingly. The top three sediment horizons (i.e. 0–1, 1–3 and 3–5 cm), were analysed in toto. Macrofauna were identified to higher taxa levels, and polychaetes to species level and counts of species/taxa recorded for each site. AphiaIDs have been assigned to the samples - where identification was only possible to genus or family level, the aphiaIDs for genus and family have been supplied. The supplied aphaIDs are those that were acceptable at the time of the analysis and not their more recent superseding terms. This cruise was part of the HERMIONE project and the data formed the basis of L. Gunton's PhD thesis 'Deep-Sea Macrofaunal Biodiversity of the Whittard Canyon (NE Atlantic)'.