Auftauing

Auftauing, more commonly translated as thawing or defrosting, is the phase transition in which a frozen substance absorbs heat and changes from a solid to a liquid. The term derives from the German verb auftauen, meaning to thaw, and in English usage it is rare outside technical or bilingual contexts.

Physically, thawing requires latent heat of fusion. For ice near 0°C, about 334 kilojoules of energy are needed to melt each kilogram. The rate of thawing is governed by heat transfer from the surrounding environment and by the material’s properties: the temperature difference, thermal conductivity, surface contact, thickness, and whether heat moves mainly by conduction, convection, or radiation. In layered systems such as soil or ice in contact with air or water, thawing can be nonuniform, with surface melting often proceeding faster than interior melting and with refreezing occurring under damp or fluctuating conditions.

Applications and contexts vary. In natural settings, thawing occurs seasonally in temperate climates and forms the active layer in permafrost regions, where seasonal warming deepens the zone of unfrozen ground. In human contexts, thawing is used to prepare frozen foods for cooking or consumption; methods include refrigeration, cold-water immersion, or microwave thawing, each with distinct effects on texture, microbial activity, and nutrient retention. In engineering and climate science, thawing of soil and permafrost can cause ground subsidence and structural instability, while large-scale thawing of permafrost can contribute to climate feedbacks through released greenhouse gases.

See also: thaw, defrosting, permafrost, latent heat.