File:NesbittGeodynamicsFinal.pdf

The St. Elias Mountains of southeastern Alaska, one of the highest coastal mountain ranges in the world, are also home to some of the world’s highest exhumation rates. High precipitation, topographic relief, and mildly cold mean annual temperatures allow the St. Elias to host one of the largest volumes of continental, sub-arctic ice in the world. This ice comprises the remnants of the ancestral Cordilleran Ice Sheet. Understanding the landscape change caused by past and present ice masses in this region is crucial to understanding the region’s tectonic evolution. This study uses ice velocity and internal cohesive strength of geologic material to inform estimates of erosion rate and volume over two time scales that differ by two orders of magnitude. We find that glaciers account for an average of ∼5 mm yr −1 of erosion in the St. Elias from 2013-2017; a value that nearly doubles during the 2013-2014 surge of Bering Glacier. Glaciers and ice sheets cause an average of 15-20 mm yr −1 of erosion in the region since 115 kya, and erosion nearly doubled during the last glacial maximum (LGM) ∼18 kya. 60% of exhumation is occurring at elevations below 2000 m above mean sea level. In total, 4.3 ∗ 10 6 km 3 (∼1.6 km) has been exhumed from the orogen over the last 115 ka. We also report results from projects that used these outcomes to drive their models. Although the calculated erosion rates are corroborated by sedimentation rates in the Gulf of Alaska, spatial variance estimates of erosion could be significantly improved by using a computational method that more accurately represents the physical forces driving glacial erosion.