275-8 Kinematic and Geophysical Evidence for the Loss of Alpine Permafrost from Rock Glaciers on Mt. Mestas (Colorado)

Abstract:

This study focuses on Mt. Mestas, in the Spanish Peaks region of Colorado, where rock glaciers developed at relatively low elevations during the Late Quaternary.  In addition to supporting local ecosystems, these rock glaciers serve as important water resources for local communities, owing to the accessibility provided by their low altitudes.  Rock glacier kinematics on Mt. Mestas were measured using Interferometric Synthetic Aperture Radar (InSAR) spanning 2015 through 2025.  Vertical and horizontal displacements were differentiated using multiple satellite viewing geometries. Further kinematic constraints were provided by repeated surveys of sparse monument networks using GNSS also spanning 2014 through 2025. Collectively, these observations demonstrate a larger component of downward vertical displacement than would be expected by down-slope movement of the rock mass. This implies significant settlement likely resulting from the loss of volume of ice lenses. The subsurface structure of one rock glacier was further investigated using electrical resistivity tomography (ERT). These results depicted the spatially variable distribution of subsurface ice, as well as suggesting the presence of ice lenses. The results further demonstrate how a larger rock glacier body has likely separated into smaller rock glaciers as the landform has degraded during the Holocene. The present-day rates of surface settlement provide first-order constraints on the rates of ice loss, which has implications for the longevity of the freshwater resource provided by the rock glaciers.

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