HR: 0800h
AN: C21C-1126    [Abstracts]
TI: The Spatial Response of Snow Isotopes to Varying Storm Types on a Lee-slope Glacier in the Canadian Rocky Mountains
AU: * Moran, T
EM: tamoran@ucalgary.ca
AF: University of Calgary, Department of Geography, Earth Sciences 356, 2500 University Dr., Calgary, AB T2N 1N4 Canada
AU: Sinclair, K
EM: kate.sinclair@ucalgary.ca
AF: University of Calgary, Department of Geography, Earth Sciences 356, 2500 University Dr., Calgary, AB T2N 1N4 Canada
AU: Marshall, S
EM: marshals@ucalgary.ca
AF: University of Calgary, Department of Geography, Earth Sciences 356, 2500 University Dr., Calgary, AB T2N 1N4 Canada
AB: Previous studies of snow isotopes show a well-documented trend of decreasing isotopic values with increasing elevation on the windward slopes of mountain ranges (Dansgaard, 1964). This trend, however, has not been corroborated on lee-slopes, where the isotopic pattern often becomes increasingly difficult to interpret. The Robertson Glacier located in the Canada Rocky Mountains provides a unique site for the study of snow isotopes because it receives wintertime precipitation from both the west and southeast (depending on the position of the Arctic Low). These differences in storm type result in contrasting isotopic signals with elevation found in wintertime snow pack on the Robertson Glacier. During the winter of 2002 and 2003/2004 a total of seven major snowfall events on the north-face of Robertson Glacier were sampled and analyzed for their δ¹⁸O isotope composition. Snow samples were collected along an elevation transect ranging from 1905 m to 2900 m, at intervals of approximately 100m elevation gain. Meteorological data from an Automated Weather Station (AWS) in the area and from Environment Canada weather stations, in addition to satellite imagery, were used to determine storm trajectory and vapour source origin. Results of the seven snowfall events sampled indicate that two storms exhibit Dansgaard's well-documented isotopic trend for windward slopes (i.e. decreasing isotopic values with increasing elevation) with the remaining five snowfall events showing the reverse (i.e. increasing isotopic values with increasing elevation). The unique position of the Robertson Glacier and its susceptibility to both westerly and upslope slope storms is thought to explain the two different trends in isotopic values. Storms originating from the west continue to precipitate beyond the point of highest elevation (2900m) down the lee-lope of the Robertson Glacier; resulting in an increasing isotopic trend with increasing elevation. Conversely, storms that have originated from the southeast; bring precipitation upslope onto the Robertson Glacier and result in decreasing isotopic values with increasing elevation. These results suggest that the reverse trends in isotopic values can be attributed to storm type and thus the direction of precipitation delivery.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0720 Glaciers
DE: 0736 Snow (1827, 1863)
DE: 4870 Stable isotopes (0454, 1041)
SC: Cryosphere [C]
MN: Fall Meeting 2005