The majority of glaciers and ice sheets flow on a bed of loose and thawed sediments. These sediments are weakened by pressurized glacial meltwater, and their lubrication accelerates the ice movement. In formerly-glaciated areas of the world, for example Northern Europe, North America, and in the forelands of the Alps, the landscape was reshaped and remolded by past ice moving the sediments along with its flow. Sediment movement is also observed under current glaciers, both the fast-moving ice streams of the Greenland and Antarctic ice sheets, but also smaller glaciers in the mountainous areas of Alaska, northern Scandinavia, and elsewhere. The movement of sediment could be important for the progression of glaciations, and influence how resilient marine-terminating ice streams are against sea-level rise.
Today, the Nature-group journal Communications Earth & Environment published my paper on sediment beneath ice. Together with co-authors Liran Goren, University of the Negev (Israel), and Jenny Suckale, Stanford University (California, USA), we present a new computer model that simulates the coupled mechanical behavior of ice, sediment, and meltwater. We calibrate the model against real materials, and provide a way for including sediment transport in ice-flow models. We also show that water-pressure variations with the right frequency can create create very weak sections inside the bed, and this greatly enhances sediment transport. I designed the freely-available program cngf-pf for the simulations.
Water pressure fluctuations control variability in sediment flux and slip dynamics beneath glaciers and ice streams
Rapid ice loss is facilitated by sliding over beds consisting of reworked sediments and erosional products, commonly referred to as till. The dynamic interplay between ice and till reshapes the bed, creating landforms preserved from past glaciations. Leveraging the imprint left by past glaciations as constraints for projecting future deglaciation is hindered by our incomplete understanding of evolving basal slip. Here, we develop a continuum model of water-saturated, cohesive till to quantify the interplay between meltwater percolation and till mobilization that governs changes in the depth of basal slip under fast-moving ice. Our model explains the puzzling variability of observed slip depths by relating localized till deformation to perturbations in pore-water pressure. It demonstrates that variable slip depth is an inherent property of the ice-meltwater-till system, which could help understand why some paleo-landforms like grounding-zone wedges appear to have formed quickly relative to current till-transport rates.
It is a substantial task to prepare a scientific publication. The commit counts below mark the number of revisions done during preparation of this paper:
- Main article text: 239 commits
- Supplementary information text: 35 commits
- Experiments and figures: 282 commits
- Simulation software: 354 commits