Abstract
The distribution and drainage of meltwater at the base of glaciers sensitively affects fast ice flow. Previous studies suggest that thin meltwater films between the overlying ice and a hard-rock bed channelize into efficient drainage elements by melting the overlying ice. However, these studies do not account for the presence of soft deformable sediment observed underneath many West Antarctic ice streams, and the inextricable coupling that sediment exhibits with meltwater drainage. Our work presents an alternate mechanism for initiating drainage elements such as canals where meltwater films grow by eroding the sediment beneath. We conduct a linearized stability analysis on a meltwater film flowing over an erodible bed. We solve the Orr–Sommerfeld equation for the film flow, and we compute bed evolution with the Exner equation. We identify a regime where the coupled dynamics of hydrology and sediment transport drives a morphological instability that generates spatial heterogeneity at the bed. We show that this film instability operates at much faster time scales than the classical thermal instability proposed by Walder. We discuss the physics of the instability using the framework of ripple formation on erodible beds.
Highlights
Liquid water is present underneath more than half of the Antarctic Ice Sheet [1]
The primary motivation for our analysis here is to understand the physical processes leading to the initiation of efficient drainage in the along-flow direction such as till-incised canals
Our main motivation is to understand the initiation of efficient drainage elements for which the main axes are approximately aligned with the main flow direction, as is the case for canals incised into the till [32,33]
Summary
Liquid water is present underneath more than half of the Antarctic Ice Sheet [1]. The hydrological environments in which this water is stored and transported are2019 The Authors. Liquid water is present underneath more than half of the Antarctic Ice Sheet [1]. The hydrological environments in which this water is stored and transported are. Diverse, ranging from subglacial lakes to water-saturated wetlands situated underneath fast flowing ice [2]. The drainage systems underneath ice streams, corridors of rapid royalsocietypublishing.org/journal/rspa Proc.
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