Ice thickness, crust and sea level: ICE-6G_C (VM5a), Peltier, Argus & Drummond 2015, JGR Solid Earth 120; 1° grid.

Dated ice margins: DATED-1, Hughes et al. 2016, Boreas 45 (PANGAEA 848117). British Isles and the western North Sea: BRITICE-CHRONO, Clark et al. 2022, Boreas 51 (PANGAEA 945729).

Mountain glaciers outside the ice sheets (Alps, Pyrenees, Carpathians, Balkans, Apennines, Caucasus …): ICE-6G_C has none there. Shown is a rough estimate from published last-glacial snowline altitudes (e.g. Hughes & Woodward 2017), moved with the global temperature — indicative, not a reconstruction.

Vegetation (Biomes): LPJ-GUESS biomes, Allen et al. 2020, J. Biogeogr. 47; glacial forest cover corrected with pollen, Davis et al. 2024 (Clim. Past 20) and BIOME 6000 (Harrison 2017); Holocene forest cover from pollen, Zanon et al. 2018 (Front. Plant Sci. 9). Simplified to six classes.

Terrain: ETOPO 2022, 15″ (NOAA). Temperature: LGMR, Osman et al. 2021, Nature 599. Polders: Natural Earth 1:10m land.