Library Item
Stable isotopic exchange rate constant between snow and liquid water
Description:
The isotopic exchange rate between liquid water and ice is crucial in determining the isotopic evolution of a snowpack and its melt. The rate constant for oxygen isotopic exchange has been reported by Taylor et al. [Taylor, S., Feng, X., Renshaw, C.E., Kirchner, J.W., 2002a. Isotopic evolution of snowmelt-2. Verification and parameterization of a one-dimensional model using laboratory experiments. Water Resources Research 38(10), 1218. doi:10.1029/2001WR000815] using three melting experiments with different column heights and melting rates. In this work, we obtained the hydrogen isotopic exchange rate constant using samples from two out of three experiments in Taylor et al. [Taylor, S., Feng, X., Renshaw, C.E., Kirchner, J.W., 2002a. Isotopic evolution of snowmelt-2. Verification and parameterization of a one-dimensional model using laboratory experiments. Water Resources Research 38(10), 1218. doi:10.1029/2001WR000815]. The 1-D model developed by Feng et al. [Feng, X., Taylor, S., Renshaw, C.E., Kirchner, J.W., 2002. Isotopic evolution of snowmelt-1. A physically based one-dimensional model. Water Resources Research 38(10), 1217. doi:10.1029/2001WR000814] was fit to the isotopic results by adjusting the value of two parameters, the isotopic exchange rate constant (kr) and the fraction of ice participating in the exchange (f).
We report that the best estimated kr values are from 0.070 to 0.19 h-1 for oxygen isotopic exchange between liquid and ice, and 0.078 to 0.20 h-1 for hydrogen exchange. The model results suggest that f, the fraction of ice involved in the isotopic exchange, increases with increasing wetness of snow, and is related to snow metamorphism. We discuss the physical significance of the observed variations in kr and f.
The relationship between δD and δ18O in the melt water is modeled, and the slope is close to 6. This slope is significantly different from the slope of the meteoric water line, while it is close to the ratio of ice–liquid fractionation of hydrogen to that of oxygen.
