275-7 Accelerating Glacier Retreat along the Colorado Front Range

Abstract:

Colorado's Front Range hosts 16 named glaciers and perennial snowfields, most smaller than 0.1 km² and perched at high elevations (~3600 m) in east- to northeast-facing cirques. We present a multi-decadal geodetic mass balance record for a subset of these glaciers spanning 1963 to 2025, synthesizing historical aerial images, airborne lidar, and structure-from-motion photogrammetry from low-altitude aircraft surveys. At Andrews Glacier, geodetic mass balance rates reveal a pronounced acceleration in mass loss: -0.02 m w.e. yr⁻¹ (1963–2010), -0.16 m w.e. yr⁻¹ (2010–2020), and -0.94 w.e. yr⁻¹ (2020–2025), consistent with regional summer warming trends documented in ERA5 climate reanalysis data. For Arapaho Glacier, the rate of mass loss is even more marked, increasing from -0.35 m w.e. yr⁻¹ (2010–2020) to -1.2 m w.e. yr⁻¹ (2020–2025). Local topographic controls—including shading, debris cover, wind redistribution of snow, and avalanche inputs—modulate the pace of retreat between individual glaciers despite comparable regional climate forcings. Extrapolating current thinning rates against ground-penetrating-radar-measured ice thicknesses suggests that several of these glaciers may disappear within the next 25–65 years. These findings are the longest available observational record of alpine glacier change along the Colorado Front Range and underscore the vulnerability of small glaciers to ongoing atmospheric warming.

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