Abstract
Glacier surges materialize as a wide but continuous spectrum of observed behavior, hinting at the existence of a universal driving mechanism. While such a mechanism is inherently difficult to describe, recently proposed models of glacier surging could complement each other towards a universal model of oscillatory flow. Systems based views of surging, such as the enthalpy model, aim at unifying a wide variety of glacier characteristics known to affect ice flow, such as mass balance gradients, ice thermodynamics, and basal hydrology. In turn, process-based views of surging describe ice flow variability as the consequence of transient basal friction, placing emphasis on basal mechanics and the material and morphological properties of the glacier bed. When combining both approaches within a wider framework, a systems-based component could be used to monitor basal conditions over time and space. These basal conditions could then effectively be used to force the boundaries of a process-based component describing transient basal drag and ice velocities, thus encompassing ice-flow instabilities. The goal of the framework outlined above is to consolidate and contextualize recent progress in surge understanding, rather than provide a definitive model of glacier surges. Systems- and process-based views of surging are not mutually exclusive but rather complement each other towards a more complete description of the surge mechanism. Their interactions could be explored further through numerical modelling, remote sensing, and field observations. Ongoing observations, notably on Sit' Kusa (also known as Turner Glacier), Alaska, aim at deriving spatio-temporally detailed information on mass and subglacial water fluxes, as well as on basal properties throughout the surge cycle. Such observations could help to identify the relative contributions of systems- and process-based components to surging, and shed light on how their interactions drive surge behavior.