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Paper No. 9-5 Presentation Time: 8:00 AM-12:00 PM ISOTOPIC EVOLUTION OF WATER IN A SIERRA SNOWPACK

Summary: Paper No. 9-5 Presentation Time: 8:00 AM-12:00 PM ISOTOPIC
DERBY, Michael, PEARLMAN, Aaron, AREHART, Greg B., and POULSON, Simon R.,
Geological Sciences, Univ Nevada, Reno, Geological Sciences MS-172, Univ Nevada, Reno,
Reno, NV 89557, derby@unr.nevada.edu
We analyzed the isotopic composition (D values) of several profiles of precipitated waters in
the Sierra Nevada winter 2001/2002 snowpack over the course of the winter as the snowpack
accumulated. Snow pits were dug to the ground and observations regarding snow crystal
identification and implications are considered along with vertical temperature profiles, vertical
hardness profiles, and vertical isotopic profiles. Measured D values range from -161 to -
48. Individual snowfall events with greatly negative isotopic values are identified and
correlated to specific weather events. At least several major storms are identifiable because of
their greatly negative D values when compared to the bulk of the snowpack. These low D
values persisted throughout the season in nine snow pits within a 7 x 20 m area isolated from
skier and snow machine traffic. The results show that although the morphology of crystals in the
snowpack changes over the course of the winter isotopic characteristics of the snowpack remain
consistent and that we can track these trends throughout the season as the snowpack matures.
These highly negative features persist throughout the season and show little to no vertical
migration due to vapor transport. The implication is that there are insufficient thermal gradients
developed within this Sierra snowpack to foster significant vapor transport of water in the


Source: Arehart, Greg B. - Department of Geological Sciences, Mackay School of Mines, University of Nevada, Reno


Collections: Geosciences