Development of a Local Meteoric Water Line For Areas Near the Teton Crest
in Grand Teton National park, Wyoming
By Emily Baker
Whitman College, Walla Walla WA
Glaciers in Grand Teton National Park, Wyoming, are undergoing rapid retreat. Stable isotopes in water can be useful tracers for determining environmental conditions in areas containing glaciers, and can help predict their long-term health. In late August 2009, samples of snow, streams, and lakes were sampled synoptically in three basins in Cascade Canyon near the Teton crest. From these three watersheds – two glacially-fed, and one snow-fed – a total of 58 water samples were collected from hydrological endmembers, including snow, meltwater streams, lakes, and outlet streams. Following linear-regression analysis, the samples revealed a Local Meteoric Water Line (LMWL) defined by the equation δ2H= 6.252 δ18O - 19.60 (r2 = .92). Comparison to both the Global Meteoric Water Line (GMWL) and the LMWLs for southeastern Idaho and western Wyoming (Benjamin et al., 2004), and Yellowstone National Park (Kharaka et al., 2002) reveals the high relative importance of post-depositional fractionation processes in watersheds of the high Tetons. Comparison of deuterium-excess and the slope of the meteoric water line gives important insight into climatic conditions near the park’s glaciers. Analysis by basin shows local importance of post-depositional modification of the stable isotope signal by snow melt, evaporation from lakes, erosive wind loss of snow, and the moderating presence of small alpine glaciers. Development and analysis of a LMWL specific to the high Teton alpine glaciers will be helpful for future studies which seek to determine the health of the glaciers, and the proportion of glacial melt in late summer runoff.