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Definition:
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The freezing of meltwater due to a change in pressure alone. The term is often used for 'pressure melting and regelation'. Regelation happens because the pressure-melting point of ice varies inversely with pressure. Water in equilibrium with ice will freeze, releasing the latent heat of fusion, 333.5 k: J kg-1, if there is a decrease of pressure, as on the downglacier face of a bump in the bed of a temperate glacier. Ice in equilibrium with water will melt if there is an increase of pressure, as on the upglacier face of the bump. However, the latent heat of fusion must be supplied for this change of phase. A natural source is the latent heat released by regelation on the downglacier face. If pressure melting and regelation are unequal, there will be a contribution to basal ablation or basal accumulation. Smaller bumps are more favourable to pressure melting and regelation than larger ones. The Russian word 'regelatsiya' refers to refreezing rather than to regelation.
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