Equilibrium oxygen- and hydrogen-isotope fractionation between ice and water

We have performed high-precision measurements of the isotope-fractionation factors between ice and water. Ice was grown from a stirred water mass on a cooling plate. The freezing velocity was varied, keeping the stirring rate of the water constant, so that the equilibrium fractionation factors could be determined by extrapolating to zero freezing velocity. The resulting values are

∝ (18O/16O) = 1.00291 ± 0.00003 and

∝ (D/H) = 1.0212 ± 0.0004.

Non-equilibrium freezing of lake and sea ice is briefly discussed as well as the significance of our results for the deuterium excess in polar precipitation.