The data set consists of digital bathymetric contours taken from the International Bathymetric Chart of the Mediterranean (IBCM) chart series. Most of the IBCM sheets depict contours at depths at 0m (coastline), 20m, 50m, 100m, and 200m, and at 200m intervals thereafter, although the actual contours displayed vary slightly from sheet to sheet. The data set is included in the GEBCO Digital Atlas (GDA). Through the GDA software interface the IBCM bathymetric contours can be exported in ASCII or shapefile format. The 10 sheets of the IBCM chart series are on a Mercator Projection at a scale of 1:1 million (at 38 N). The Black Sea is included at a scale of 1:2 million. The IBCM (1st Edition) chart series was published by the Head Department of Navigation and Oceanography of the USSR Ministry of Defence, St. Petersburg, under the auspices of the Intergovernmental Oceanographic Commission (IOC) of UNESCO 1981. The bathymetric contours and coastlines from the IBCM sheets were digitised. Error checking and quality control work on the data set was carried out at BODC. The digital data set was first made available in 1988.

The GEBCO_2019 Grid is a global continuous terrain model for ocean and land with a spatial resolution of 15 arc seconds. The grid uses as a ‘base’ Version 1 of the SRTM15_plus data set (Sandwell et al). This data set is a fusion of land topography with measured and estimated seafloor topography. It is largely based on version 11 of SRTM30_plus (5). 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, and from a number of international and national data repositories and regional mapping initiatives. The GEBCO_2019 Grid represents all data within the 2019 compilation. The compilation of the GEBCO_2019 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. The majority of the compilation was done using the 'remove-restore' procedure (Smith and Sandwell, 1997; Becker, Sandwell and Smith, 2009 and Hell and Jakobsson, 2011). This is a two stage process of computing the difference between the new data and the ‘base’ grid and then gridding the difference and adding the difference back to the existing ‘base’ grid. The aim is to achieve a smooth transition between the 'new' and 'base' data sets with the minimum of perturbation of the existing base data set. 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_2019 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).

As part of the the CHIMNEY project (NERC grant NE/N016130/1), multibeam bathymetry data were collected during RRS James Cook cruise JC152 to a subsea chimney structure in the northern North Sea around Scanner Pockmark in August-September 2017. Multibeam data were acquired using a Kongsberg EM-710 multibeam echosounder and processed by the JC152 Science Party. In conjunction with seismic profile data acquired on the same cruise, these data will help scientists understand the surface and internal structure and origin of the chimney structure. This will facilitate estimation of the permeability of the chimney and its surroundings, and enable leakage pathways to be determined. The potential for past oil and gas reservoirs and saline aquifers to be used as Carbon Capture and Storage (CCS) reservoirs of atmospheric CO2 can subsequently be explored. The safety of storing CO2 in such reservoirs is dependent on fully exploring the risks of any leakage via such chimney structures, which the CHIMNEY project will investigate. CHIMNEY is funded by the Natural Environment Research Council (NERC), and involves scientists from the National Oceanography Centre, Southampton and the University of Edinburgh. Investigators will work closely with project partners GEOMAR, Lawrence Berkley National Laboratory, CGG and Applied Acoustics. The project is complementary to the EU-funded Horizon 2020 project: Strategies for Environmental Monitoring of Marine Carbon Capture and Storage (STEMM-CCS).

This data set consists of a bathymetric grid derived from multibeam bathymetry data from cruise JC071. The bathymetric grid was created by gridding the cleaned raw multibeam data from JC071 at 1/64 arc-minute intervals using a nearneighbour gridding algorithm from the Generic Mapping Tools (GMT) software system. The data set covers an approximate one degree square with the minimum and maximum longitude and latitude co-ordinates: 17.016667W-16.216667W; 48.78333N-49.28333N. This is located in the Northeast Atlantic Ocean area. The data were collected from 7th-8th May 2012 using an EM120 Multibeam Echo-sounder. The cruise was part of the Porcupine Abyssal Plain (PAP): sustained ocean observation project. The bathymetry data were collected on an opportunistic basis during the cruise. The cruise was operated by the National Oceanography Centre (NOC), equipment operated by National Marine Facilities Sea Systems. The bathymetric grid was created by BODC for contributing to the EMODnet High Resolution Seafloor Mapping (HRSM) Project.

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.

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.