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Abel, Kali M ¹

¹ University of Colorado, Boulder and INSTAAR

Yosemite’s small glaciers are rapidly retreating, impacting a critical source of late-season cold water for the upper Tuolumne River ecosystem. Addressing quantitatively how glaciers will respond to present and future climate change demands that we understand how small alpine glaciers have responded to past climate change. Previous research suggests that small alpine glaciers often respond to climate changes by retreating into topographic niches, where they receive less direct solar radiation and can be maintained by high snow fluxes associated with avalanching and headwall protection.

We report results from a project targeting the Lyell and Maclure Glaciers in Yosemite National Park. We aim to understand their response to climate change through and subsequent to the Little Ice Age by combining archival records of glacier position through time, instrumental records augmented by new instrumentation, and analysis of new local tree-ring records. Using the instrumental record and tree cores, we calibrate tree ring width with instrumental records for the area, verifying the correlation between tree ring growth and climate variations on a local level. Tree ring records near Lyell and Maclure Glaciers expand the record into the Little Ice Age (as far back as 1590) in the context of the glaciers’ local climate. This work allows us to drive a glacier model using the tree ring chronology as a proxy for past ELA positions. For the Lyell and Maclure glaciers, our data provide a detailed picture of how these glaciers have responded to previous changes in localized climate and indicate what would be reasonable to expect in terms of future retreat rates and magnitudes.