2022 CSDMS meeting-024


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Numerical modeling of subglacial sediment entrainment

Ethan Pierce, (he/him/his),University of Colorado Boulder Boulder Colorado, United States. ethan.pierce@colorado.edu
Irina Overeem, University of Colorado Boulder Boulder Colorado, United States. irina.overeem@colorado.edu

At the margins of many glaciers, we observe visually-striking layers of concentrated sediment incorporated into ice near the base of the glacier. Despite the prevalence of these ice-sediment facies, sediment transported in basal ice is rarely quantified in the overall sediment transport budget for glacial systems. Previous facies descriptions have been linked to formation mechanisms that depend on specific configurations of the topography or hydrology beneath a glacier, which remains inconsistent with observations of similar facies across disparate regions, climate zones, and geologic settings. Here, we use detailed descriptions of ice-sediment facies from Mendenhall glacier, Alaska, to inform a numerical model of sediment entrainment in basal ice. We find that the overall volume of entrained sediment is strongly related to the glacier’s thermal regime near the ice-sediment interface. Further, we present a likely mechanism for the formation of dispersed ice facies that explains the natural variability in sediment characteristics observed at Mendenhall glacier and other alpine systems. These results show that ice-sediment facies are a plausible archive for understanding the subglacial environment, even in the absence of additional constraints on temperature or hydrologic connectivity at the bed.