HR: 0800h
AN: H11C-0651    [Abstracts]
TI: Isotopic Exchange Rate Constant between Snow and Liquid Water
AU: * Lee, J
EM: Jeonghoon.Lee@Dartmouth.EDU
AF: Dept. of Earth Sciences, Dept. Earth Sciences Dartmouth College 6105 Fairchild Hall, Hanover, NH 03755, United States
AU: Feng, X
EM: Xiahong.Feng@Dartmouth.EDU
AF: Dept. of Earth Sciences, Dept. Earth Sciences Dartmouth College 6105 Fairchild Hall, Hanover, NH 03755, United States
AU: Posmenrier, E S
EM: Eric.S.Posmentier@Dartmouth.EDU
AF: Dept. of Earth Sciences, Dept. Earth Sciences Dartmouth College 6105 Fairchild Hall, Hanover, NH 03755, United States
AU: Faiia, A M
EM: Anthony.M.Faiia@Dartmouth.EDU
AF: Dept. of Earth Sciences, Dept. Earth Sciences Dartmouth College 6105 Fairchild Hall, Hanover, NH 03755, United States
AB: 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. [2002] using three column melting experiments with different heights and melt rates. In this work, we obtained the hydrogen isotopic exchange rate constant using samples from two out of three experiments in Taylor et al [2002]. The 1-D model developed by Feng et al. [2002] was fit to the isotopic results by adjusting the value of two parameters: the isotopic exchange rate constant ( k_r) and the fraction of ice participating in the exchange (f). To assess whether oxygen and hydrogen isotopic exchange rate are the same, we rigorously examined uncertainties of fitting parameters for both the oxygen and hydrogen data. The optimized yielded from oxygen isotopic simulations are 0.19 hr^–1 for column A, 0.15 hr^–1 for column B, and 0.07 hr^–1 for column C. The optimized k_r yielded from hydrogen isotopic simulations are 0.20 hr^–1 for column A and 0.08 hr^–1 for column C. Although it might seem that the hydrogen exchange rate constant is slightly higher for each given column experiment, the confidence regions for the adjustable parameters show that the differences are not significant. The model results suggest that f, the fraction of ice involved in the isotopic exchange increases with increasing wetness of snow. This makes sense because the isotopic exchange rate increases with 1) increasing surface area of contact between liquid and ice and 2) the rate of dissolution and recrystallization; both being related to the wetness of snow. The best fit k_r increases with the mean pore water velocity of the snow column. It is not clear what results in the dependency of k_r on pore water velocity. One possibility is that at low flow water may be channelized, so it bypasses some of the immobile water that exchanges with the ice and not all the exchanged isotopes are reflected in the discharge. However, the model does not consider preferential flow, and this effect would thus cause a lower value of the best fit exchange rate constant.
DE: 0736 Snow (1827, 1863)
DE: 0740 Snowmelt
DE: 0798 Modeling
DE: 1847 Modeling
DE: 1873 Uncertainty assessment (3275)
SC: Hydrology [H]
MN: 2007 Fall Meeting