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

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.

Centennial‐ and Orbital‐Scale Erosion Beneath the Greenland Ice Sheet Near Jakobshavn Isbræ

“…All data needed for calculating 10 Be ages and erosion rates in the study are available at the NSF Arctic Data Center via https://doi.org/10.18739/A29S1KM49 with Creative Commons Attribution 4.0 International License (Balter‐Kennedy et al., 2021). In addition, data needed to calculate 10 Be ages from surficial bedrock samples are hosted in ICE‐D:Greenland (http://greenland.ice-d.org/).…”