The currently used "kinetic-fractionation" (KF) model of the differentialincorporation of water-molecule isotopologues into vapor-grown ice omitssurface processes on crystal facets that may be important in temperaturereconstructions. This article introduces the "surface-kinetic"fractionation model, a model that includes such surface processes, and showsthat differences in deposition coefficients for water isotopologues canproduce isotopic fractionation coefficients that significantly differ fromthose of KF theory. For example, if the deposition coefficient ofHO differs by just 5% from that of ordinary water(HO), the resulting fractionation coefficient at 20%supersaturation may deviate from the KF value by up to about ±17‰, andeven more at greater supersaturation. As a result, the surface-kinetictheory may significantly change how fractionation depends onsupersaturation. Moreover, the model introduces possible new temperaturedependencies from the deposition coefficients. These parameters need to beconstrained by new laboratory measurements.
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