Spatial heterogeneity in subglacial drainage driven by till erosion

Area of Science:

• Glaciology
• Geophysics
• Earth Science

Background:

• Meltwater drainage at glacier bases influences ice flow speed.
• Previous models focused on ice-bed melting, neglecting deformable sediments.
• West Antarctic ice streams often have soft sediment beds coupled with meltwater.

Purpose of the Study:

• To investigate an alternative mechanism for meltwater drainage initiation.
• To explore how sediment erosion by meltwater films forms drainage elements.
• To analyze the coupled dynamics of hydrology and sediment transport.

Main Methods:

• Linearized stability analysis of meltwater film flow over an erodible bed.
• Solving the Orr-Sommerfeld equation for film hydrodynamics.
• Computing bed evolution using the Exner equation.

Main Results:

• Identified a regime where coupled hydrology and sediment transport drive morphological instability.
• Demonstrated that this instability generates spatial heterogeneity at the glacier bed.
• Showed this film instability operates on faster timescales than thermal instability.

Conclusions:

• Sediment erosion by basal meltwater films offers a novel mechanism for drainage canal formation.
• This process is crucial for understanding fast ice flow, particularly in West Antarctica.
• The findings provide insights into subglacial processes analogous to ripple formation.