The distribution of an isotopic species, HDO (deuterium) or H218O (oxygen), in ice formed by the migration of a well-defined freezing front in water is dependent on the freezing rate. Development of a box diffusion model combined with the boundary layer concept leads to a possibility of prediction of the freezing rate in nature by the determination of the isotopic composition of the ice in ΔD or Δ18O. The isotopic distribution in ice formed during experiments conducted with variable freezing rates gives results in accordance with the model. Investigation on lake ice formed under well-known climatic conditions provides a further test of the model. ¿American Geophysical Union 1987