TESTING ICE CORE RECORDS IN SMALL TEMPERATE ALPINE GLACIERS

Shallow ice cores from glaciers in the Big Pine drainage, eastern Sierra Nevada, suggest that small temperate cirque glaciers may preserve valuable records of past variations in precipitation and temperature. Generally, such alpine glaciers have been overlooked for ice core studies because it has been presumed that percolating meltwater and rapid diffusion destroys any useful information, particularly stable isotopes (d18O and dD); our study tests this concept by sampling two distinct glaciers, a normal “clean” glacier, and a glacigenic rock glacier. The Palisade Glacier is the largest glacier in the Sierra Nevada, and therefore is a natural target for an ice-core study. In contrast, the small, debris-covered rock glacier at Southfork Pass seems an unlikely candidate. However, such slow-moving, debris-covered glaciers tend to preserve stable isotope stratigraphy (e.g., Steig et al., 1998). We collected two ice cores from each glacier in August, 2003, ~4-m and 6-m long from the accumulation zone of the Palisade Glacier, and 1 m and 2 m near a thermokarst pond at Southfork Pass. In addition, we sampled snow pits near the Palisades coring site in early July and early August, 2003, to constrain changes in the snowpack through the summer. The upper 1.3 m of the Palisades ice cores is dominated by loose firn with thin ice lenses; below 1.3, the cores are dominated by clear bubbly ice. The ice is entirely bubbly ice in the Southfork Pass cores, reflecting the location in the ablation zone. Preliminary analyses of the ice cores suggest both glaciers preserve stable isotope, dust, and mass-accumulation stratigraphy. Dust concentrations indicate that both span several years of accumulation. Early dD indicates significant variations are preserved in the Palisades ice cores. Results of all analyses will be available by the meeting. If early results are confirmed, they may justify more concerted efforts to recover ice cores from other similar glaciers before ongoing melting and retreat destroys them.