## 3 Data Source and Methods  
This study used the hydrate-related GIS database of the GARAH project 731166, GeoERA-GE-1, H2020 Environment ([[https://geoera.eu/projects/garah4/](https://geoera.eu/projects/garah4/)]([https://geoera.eu/projects/garah4/](https://geoera.eu/projects/garah4/)); accessed on 20 December 2020). This GIS database (GARAH_ydrates_; [57]) is INSPIRE-compliant and stores hydrate-related geological, geophysical and oceanographic information (Figure 2). It is the result of a data collection from two main groups of data: (i) data of a pan-European scope from free public databases and project results, such as EMODnet, PERGAMON and MIGRATE; and (ii) data of a regional scope from scientific organizations. The source of the data, owner and person/institution of contact is stored in each database record. The majority of the geological and geophysical evidence and indicators of marine gas hydrates of GARAH_ydrates_ came from the results of Work Package 1 of the MIGRATE COST action--ES1405 ([[https://www.migrate-cost.eu/](https://www.migrate-cost.eu/)]([https://www.migrate-cost.eu/](https://www.migrate-cost.eu/)); data given by MIGRATE COST Action to GARAH project on 31 January 2019) led by the University of Southampton and the National Oceanographic Centre, in which 21 organizations from 15 countries were involved. The MIGRATE database contains 1892 records (vector and raster) and stores information regarding direct and indirect evidence of gas hydrates. The data on direct evidence of gas hydrates are from samples described in publications. The data on indirect evidence include seismic indicators such as BSR levels and areas, gas chimneys, high reflectivity areas and velocity anomalies. Other gas hydrate information includes seabed features (gas seepage areas), heat flow data, sediment thickness models, pore water anomalies, theoretical models of the base of the GHSZ, and relief and bathymetry models. Figure 2: Geological, geophysical and oceanographic data sets used in the present paper. Marine gas hydrate evidence and indicators, and oceanographic variables stored in the GARAHy_rates data base. (**a**) Study area. (**b**) West Greenland. (**c**) Barrents Sea. EMODnet Geology marine minerals ([[https://www.emodnet-geology.eu/map-viewer/?p=marine_minerals](https://www.emodnet-geology.eu/map-viewer/?p=marine_minerals)]([https://www.emodnet-geology.eu/map-viewer/?p=marine_minerals](https://www.emodnet-geology.eu/map-viewer/?p=marine_minerals)); accessed on 1 January 2019) supplied 28 records in polygon shapefile format regarding marine gas hydrate evidence in the Gulf of Cadiz, the Barents Sea and the Black Sea. The PERGAMON database was developed by the geological surveys of Spain (IGME) and Ireland (GSI) in 2011 and 2012 in the framework of the PERGAMON COST action--ES0902 ([[https://www.cost.eu/actions/ES0902/](https://www.cost.eu/actions/ES0902/)]([https://www.cost.eu/actions/ES0902/](https://www.cost.eu/actions/ES0902/)); data given by PERGAMON Cost Action to GARAH project on 1 January 2019). This database supplied seafloor temperature data and theoretical models of the thickness of the GHSZ in the Arctic Sea. The geothermal gradient data were obtained from the global heat flow database of the International Heat Flow Commission (website: [[http://engineering.und.edu/geology-and-geological-engineering/globe-heat-flow-database/index.cfm](http://engineering.und.edu/geology-and-geological-engineering/globe-heat-flow-database/index.cfm)]([http://engineering.und.edu/geology-and-geological-engineering/globe-heat-flow-database/index.cfm](http://engineering.und.edu/geology-and-geological-engineering/globe-heat-flow-database/index.cfm)); accessed on 31 March 2020). The data were downloaded with the ODV application ([[https://odv.awi.de/](https://odv.awi.de/)]([https://odv.awi.de/](https://odv.awi.de/)); accessed on 1 February 2019).