26 Nov 2021
 | 26 Nov 2021
Status: a revised version of this preprint is currently under review for the journal ESurf.

The spatially distributed nature of subglacial sediment dynamics: using a numerical model to quantify sediment transport and bedrock erosion across a glacier bed in response to glacier behavior and hydrology

Ian Delaney, Leif S. Anderson, and Frédéric Herman

Abstract. In addition to ice and water, glaciers expel sediment. As a result, changing glacier dynamics and melt will result in changes to glacier erosion and sediment discharge, which can impact the landscape surrounding retreating glaciers, as well as communities and ecosystems downstream. To date, the available models of subglacial sediment transport on the sub-hourly to decadal-scale exist in one dimension, usually along a glacier's flow line. Such models have proven useful in describing the formation of landforms, the impact of sediment transport on glacier dynamics, the interactions between climate, glacier dynamics, and erosion. However, because of the large role of sediment connectivity in determining sediment discharge, the geoscience community needs modeling frameworks that describe subglacial sediment discharge in two spatial dimensions over time. Here, we present SUGSET_2D, a numerical model that evolves a two-dimensional subglacial till layer in response to the erosion of bedrock and changing sediment transport conditions below the glacier. Experiments employed on test cases of synthetic ice sheets and alpine glaciers demonstrate the heterogeneity in sediment transport across a glacier's bed. Furthermore, the experiments show the non-linear increase in sediment discharge following increased glacier melt. Lastly, we apply the model to Griesgletscher in the Swiss Alps where we use a parameter search to test model outputs against annual observations of sediment discharge measured from the glacier. The model captures the glacier's inter-annual variability and quantities of sediment discharge. Furthermore, the model's capacity to represent the data depends greatly on the grain size of sediment. Smaller sediment sizes allow sediment transport to occur in regions of the bed with reduced water flow and channel size, effectively increasing sediment connectivity into the main channels. Model outputs from the three test-cases together show the importance of considering heterogeneities in water discharge and sediment availability in two dimensions.

Ian Delaney et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-88', Irina Overeem, 01 Feb 2022
    • AC1: 'Reply on RC1', Ian Delaney, 23 May 2022
  • RC2: 'Comment on esurf-2021-88', Stefan Hergarten, 08 Feb 2022
    • AC2: 'Reply on RC2', Ian Delaney, 23 May 2022
  • RC3: 'Comment on esurf-2021-88', Anonymous Referee #3, 01 Mar 2022
    • AC3: 'Reply on RC3', Ian Delaney, 23 May 2022
  • EC1: 'Comment on esurf-2021-88', Frances E. G. Butcher, 14 Mar 2022
    • AC4: 'Reply on EC1', Ian Delaney, 23 May 2022
  • EC2: 'Comment on esurf-2021-88', Frances E. G. Butcher, 01 Jun 2022

Ian Delaney et al.

Ian Delaney et al.


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Short summary
This manuscript presents a two-dimensional subglacial sediment transport model, that evolves a sediment layer in response to subglacial sediment transport conditions. The model captures sediment transport in supply- and transport-limited regimes across a glacier's bed and considers both the creation and transport of sediment. Model outputs show how the spatial distribution of sediment and water below a glacier can impact the glacier's discharge of sediment and erosion of bedrock.