Ice–liquid isotope fractionation factors for ¹⁸O and ²H deduced from the isotopic correction constants for the triple point of water

Abstract

The stable isotopes of water are extensively used as tracers in many fields of research. For this use, it is essential to know the isotope fractionation factors connected to various processes, the most important of which being phase changes. Many experimental studies have been performed on phase change fractionation over the last decades. Whereas liquid-vapour fractionation measurements are relatively straightforward, vapour-solid and liquid-solid fractionation measurements are more complicated, as maintaining equilibrium conditions when a solid is involved is difficult. In this work, we determine the ice-liquid isotope fractionation factors in an indirect way, by applying the Van't Hoff equation. This equation describes the relationship of the fractionation factors with isotope-dependent temperature changes. We apply it to the recently experimentally determined isotope dependences of the triple point temperature of water [Faghihi V, Peruzzi A, Aerts-Bijma AT, et al. Accurate experimental determination of the isotope effects on the triple point temperature of water. I. Dependence on the H abundance. Metrologia. 2015;52:819-826; Faghihi V, Kozicki M, Aerts-Bijma AT, et al. Accurate experimental determination of the isotope effects on the triple point temperature of water. II. Combined dependence on theO and O abundances. Metrologia. 2015;52:827-834]. This results in new values for theH (deuterium) and O fractionation factors for the liquid-solid phase change of water, which agree well with existing, direct experimental data [Lehmann M, Siegenthaler U. Equilibrium oxygen- and hydrogen-isotope fractionation between ice and water. J Glaciol. 1991;37:23-26]. ForH, the uncertainty is improved by a factor of 3, whereas for O the uncertainty is similar. Our final results are α (H/H) = 1.02093(13), and α (O/O) = 1.002909(25), where the latter is the weighted average of the previous experimental study and this work.

Assessing the influence of lake and watershed attributes on snowmelt bypass at thermokarst lakes

“…where α * L-S is the equilibrium fractionation factor between ice and water (1.002909 for 18 O/ 16 O, 1.02093 for 2 H/ 1 H; Wang and Meijer, 2018), z is the 18 O or 2 H boundary layer thickness between the ice and water (mm), v is the velocity of ice growth (cm 2 d −1 ), and D i is the self-diffusion coefficient of 1 H 18 2 O or 1 H 2 H 16 O at 0 • C (cm 2 d −1 ). As the boundary layer and the velocity of ice growth increase, α eff moves from the value of α * L-S towards a value of 1 (i.e., no fractionation).…”