CONTINUED MOVEMENT AND ABLATION MONITORING, GALENA CREEK ROCK GLACIER, ABSAROKA MOUNTAINS, WY
New to this study is the estimation of ablation beneath the debris over 18 years of measurement by comparing actual movement to a path predicted based on local surface slope. Ablation rates average 7.4 cm/yr across the entire glacier and are greatest (up to 29.5 cm/yr) near the head of the glacier, where debris is thinnest, and least (<5 cm/yr) at the toe, where debris is thickest. Though there is no statistically significant relationship across the entire glacier, data suggest a weak trend for decreasing ablation with increasing debris thickness up to ~1.25 m. When debris is thicker, factors beyond debris thickness may have more effect on ablation rates. A trend of faster ablation near the head of the glacier and slower ablation near the toe suggests that, with a warming climate, the glacier could be “beheaded,” with the insulated toe still intact and flowing even after ice at the head stops accumulating and disappears.
Several calculations of potential paths a single boulder might travel down the length of the glacier used measured velocities from point to point along the path. They suggest a head-to-toe travel time of around 3,000 yr. The age constraint this provides is in agreement with past radiocarbon dates of 2250±35 yr on the lateral edge of the glacier near its midpoint (Konrad, 1999).
Finally, with equipment and advice provided by UNAVCO, all survey points were recorded again with PPK GPS technology, allowing for better and faster future surveys, and a three-dimensional model of the cirque headwall above the glacier was created using LiDAR scans, which will allow for future detailed studies of erosion and debris supply from the headwall.