Complementary Approaches Towards a Universal Model of Glacier Surges

Abstract

Although many convincing, diverse, and sometimes competing models of glacier surging have been proposed, the observed behavior of surging glaciers does not fit into distinct categories, and suggests the presence of a universal mechanism driving all surges. On the one hand, recent simulations of oscillatory flow behavior through the description of transient basal drag hint at a fundamental underlying process. On the other hand, the proposition of a unified model of oscillatory flow through the concept of enthalpy adopts a systems based view, in an attempt to rather unify different mechanisms through a single universal measure. While these two general approaches differ in perspective, they are not mutually exclusive, and seem likely to complement each other. A framework incorporating both approaches would see the mechanics of basal drag describing ice flow velocity and surge propagation as a function of forcing by conditions at the glacier bed, in turn modulated through the unified measure of enthalpy.

Automated Detection of Glacier Surges from Sentinel-1 Surface Velocity Time Series—An Example from Svalbard

“…At surge termination, due to low driving stress velocity decreases and friction strengthening returns following basal slip rates. Even though this strongly simplified view ignores details of cavity formation, as well as spatial propagation and influences of valley side friction, the rate and state friction model describes a surge initiation and propagation entirely through the evolution of friction on hard glacier beds [29]. The model aims to identify threshold shear stresses which friction flips from velocity strengthening to velocity weakening.…”

“…Although Thøgersen et al [4] note that mass build up is common throughout all surge-type glaciers, they underline the role of meltwater supply in weakening friction by reducing the glacier sole's ability to adhere to the bed surface. Even though these two approaches differ in perspective, Terleth et al [29] state that they are not mutually exclusive, but seem to complement each other. Despite the fact that fundamental descriptions of transient basal drag could explain the translation of high enthalpy conditions to basal slip, the mechanics are governed by the conditions they occur in.…”

Reconstructing Glacier Surge Kinematics Using a Numerical Ice‐Flow Model Applied to the Dusty Glacier, St. Elias Mountains, Canada

“…Surge‐type glaciers exhibit recurring periods of brief but vigorous ice flow with velocity increases of several orders of magnitude lasting months to years, owing to hydraulically controlled reduced effective pressure at the bed that causes dramatic increases in basal sliding (Kamb, 1987; Kamb et al., 1985). To add further complexity, regional variability in surge mechanism can involve internal thermal structure and bed rheology (e.g., Benn et al., 2019; Clarke et al., 1984; Murray et al., 2003; Terleth et al., 2021; Thøgersen et al., 2019; Truffer et al., 2000). Glacier surges are separated by prolonged periods of quiescent ice flow during which an ice reservoir accumulates due to inefficient mass discharge (e.g., Jansson et al., 2003), eventually fueling subsequent surges.…”

Multi-scale variations of hydro-mechanical conditions at the base of the surge-type glacier Kongsvegen, Svalbard

“…Water pressure at the glacier base directly influences ice-bed coupling, as well as it affects shear strength of the till (Lliboutry, 1968;Clarke, 2005;Damsgaard et al, 2020;Zoet and Iverson, 2020;Hansen and Zoet, 2022;Tsai et al, 2022). This doubletracked influence gives rise to complex behavior in the relationship between water pressure and basal motion, with an exact formulation still being debated (Benn et al, 2019;Thøgersen et al, 2019;Terleth et al, 2021;Gimbert et al, 2021a;Gilbert et al, 2022). Whereas high water pressure weakens the ice-bed coupling and therefore promote sliding, low water pressure has the opposite effect.…”