a–d, Model results for a fixed methanogenic depth (100 m) but varying methanogenic rates (R2 to R10; that is, 2 × 10−15 to 10 × 10−15 grams CH4 per gram of sediment per second). e–h, Outputs of model runs under a fixed methanogenic rate (5 × 10−15 grams CH4 per gram of sediment per second) but varying methanogenic depths (20–100 m). a, b, e, f, Vertical profiles of methane solubility, dissolved methane and methane hydrates; methane concentrations are normalized to equilibrium concentration. c, g, Time required for methane hydrate formation under the modelled conditions. d, h, Diffusive CH4 flux at the sediment–ice interface under methane hydrate conditions assuming three different catchment cover areas for methane hydrates (that is, 10%, 50% and 100% of the LG catchment), compared to the three lateral flux scenarios (a, b, d; Fig. 2); see Supplementary Information 2f.