Centennial- and orbital-scale erosion beneath the Greenland Ice Sheet

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Authors

Allie Balter-Kennedy , Nicolás E. Young, Jason P. Briner, Brandon L. Graham, Joerg M. Schaefer

Abstract

Erosion beneath glaciers and ice sheets is a fundamental Earth-surface process dictating landscape development, which in turn influences ice-flow dynamics and the climate sensitivity of ice masses. The rate at which subglacial erosion takes place, however, is notoriously difficult to observe because it occurs beneath modern glaciers in a largely inaccessible environment. Here, we present 1) cosmogenic-nuclide measurements from bedrock surfaces with well constrained exposure and burial histories fronting Jakobshavn Isbræ in western Greenland to constrain centennial-scale erosion rates, and 2) a new method combining cosmogenic nuclide measurements in a shallow bedrock core with cosmogenic-nuclide modelling to constrain orbital-scale erosion rates across the same landscape. Twenty-six 10Be measurements in surficial bedrock constrain the erosion rate during historical times to 0.4–0.8 mm yr-1. Seventeen 10Be measurements in a 4-m-long bedrock core corroborate this centennial-scale erosion rate, and reveal that 10Be concentrations below ~2 m depth are greater than what is predicted by an idealized production-rate depth profile. We utilize this excess 10Be at depth to constrain orbital-scale erosion rates at Jakobshavn Isbræ to 0.1–0.3 mm yr-1. The broad similarity between centennial- and orbital-scale erosion rates suggests that subglacial erosion rates have remained relatively uniform throughout the Pleistocene at Jakobshavn Isbræ.

DOI

https://doi.org/10.31223/X5862Q

Subjects

Earth Sciences, Geochemistry, Geomorphology, Glaciology

Keywords

Cosmogenic-nuclide exposure dating, Quaternary geochronology, Geomorphological geochronology, Subglacial erosion

Dates

Published: 2021-08-31 14:40

Last Updated: 2021-08-31 21:40

License

CC BY Attribution 4.0 International

Additional Metadata

Data Availability (Reason not available):
We are in the process of submitting these data to ICE-D:Greenland (http://greenland.ice-d.org) and the NSF Arctic Data Center (https://arcticdata.io).

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