Spatial Variability of Snow Water Isotopes in Montane Southeastern Wyoming
Abstract
Prediction of snowmelt runoff from Rocky Mountain annual snowpack remains highly uncertain. Progress is limited by our understanding of how widespread vegetation disturbances from beetle kill and fire, coupled with regional climate changes, influence spatial patterns of snowpack development and evolution. We examined spatial patterns of snow water isotope content, snow depth and density and snow water equivalence in the Medicine Bow Range, Wyoming at peak snowpack in April 2013. The stable isotope composition of snowpack integrates patterns of accumulation, redistribution, sublimation, melt and condensation. Yet the relative importance of these processes and their isotope effects across highly heterogeneous terrain are poorly documented. Physical processes affecting isotopic exchange and fractionation in snowpack, including temperature, relative humidity, turbulent versus laminar flow, and radiation vary at local and catchment scales. Fifteen 150-m snow transects were completed over a variety of cover types and disturbance areas across 2400 to 3200 m elevation. δ2H and δ18O ratios were determined on snow water from the four positions along each transect and from individual snowfall events collected February through April at a single site at 2743 m elevation near the transect locations. δ2H and δ18O values of snowpack all fell on the local meteoric water line, indicating very limited kinetic isotope effects during snow-atmosphere vapor exchange. A decrease of 4 and 0.5 per mil per 100 m increase in elevation was observed in δ2H and δ18O, respectively, across all transect locations. Variance (standard deviation) among the four samples within each transect increased with elevation, ranging up to 46 per mil for δ2H and 13.0 per mil for δ18O at the highest elevation sites. Such local-scale heterogeneity in isotopic composition may reflect varying patterns and magnitudes of accumulation and/or redistribution. Relationships between hydrometeorological forcings and isotope effects on snow water, specifically sublimation, equilibrium vapor exchange, and redistribution, will be investigated further to better understand catchment-level heterogeneity in snowpack evolution. This future research will allow for better characterization of how snowmelt runoff changes in Rocky Mountain watersheds.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.C41B0595K
- Keywords:
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- 0736 CRYOSPHERE Snow;
- 0454 BIOGEOSCIENCES Isotopic composition and chemistry;
- 1631 GLOBAL CHANGE Land/atmosphere interactions;
- 1863 HYDROLOGY Snow and ice