HR: 17:45h
AN: C44A-08    [Abstracts]
TI: Testing Environmental Records From Ice Cores of a Temperate Alpine Glacier
AU: * Gillespie, A J
EM: gillesa@cc.wwu.edu
AF: Western Washington University, Geology Department 516 High Street, Bellingham, WA 98225-9080 United States
AU: Clark, D H
EM: dhclark@cc.wwu.edu
AF: Western Washington University, Geology Department 516 High Street, Bellingham, WA 98225-9080 United States
AU: Steig, E J
EM: steig@ess.washington.edu
AF: University of Washington, Earth and Space Sciences 63 Johnson Hall, Seattle, WA 98195 United States
AU: McConnell, J
EM: Joe.McConnell@dri.edu
AF: Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512 United States
AB: Low-latitude temperate alpine glaciers are largely overlooked but potentially useful archives of paleoenvironmental data; although smaller and shorter-lived than polar glaciers, their position adjacent to areas of dense population makes these glaciers attractive research targets. The Palisade Glacier is the largest glacier in the Sierra Nevada, and thus most likely to contain a reasonably unaltered physical and chemical record for the region. We collected two ice cores, ~4-m and 6-m long, from the uppermost bench on the glacier in August, 2003. Subsamples of the ice cores were analyzed for stable isotopes (d18O and dD), trace elemental abundance, and mass-accumulation stratigraphy. In addition, we sampled snow pits near the coring site in early July and early August 2003, and late June 2004 to constrain physical and isotopic changes in the snowpack through the summer meltseason. A SNOTEL site in the same drainage basin provides local records of daily precipitation and temperature, approximately 2000 feet below Palisade Glacier Our results suggest that despite recent thinning, the Palisade glacier preserves both isotopic and elemental stratigraphy. Annual layers are most apparent in the trace element concentrations, which indicate the cores preserve 4-5 years of accumulation, probably from the mid-to late1990's. A heavy concentration of the dust at the surface, combined with snow accumulation records from nearby SNOTEL sites, indicate that all snow from the previous 6 years (since winter of 1997/98, the last above-average snow year in the basin) was lost to ablation. Significantly lower visible dust concentrations in the underlying layers indicate that the core site had net accumulation during the preceding 4 years, in agreement with the SNOTEL record. Stable isotopes co-vary in the cores, coincident with the dust stratigraphy. In addition, the dD/d18O ratios closely resemble the trend of the global meteoric water line, suggesting that post-depositional melting and fractionation have been minimal. These results lend further support to previous studies (e.g., Naftz et al., 1993; Steig et al., 1998) that indicate that small temperate glaciers can preserve valuable, if complex, records of past environmental change. Further coring is needed to confirm our results, and to test viability of deeper ice in this or other glaciers.
DE: 3344 Paleoclimatology
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 1040 Isotopic composition/chemistry
DE: 1065 Trace elements (3670)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting