Modelled subglacial floods and tunnel valleys control the lifecycle of transitory ice streams

Abstract

Abstract. Ice streams are corridors of fast-flowing ice that control mass transfers from continental ice sheets to oceans. Their flow speeds are known to accelerate and decelerate, their activity to switch on and off, and even their locations to shift entirely. Our analogue physical experiments reveal that a lifecycle incorporating evolving subglacial meltwater routing and bed erosion can govern this complex transitory behaviour. The model ice streams switch on when subglacial water pockets drain as marginal outburst floods. Then they decelerate as basal coupling increases as a consequence of the lubricating water drainage system spontaneously organising itself into channels that erode tunnel valleys. They surge or jump in location when these water drainage systems maintain low discharge but they ultimately switch off when tunnel valleys have expanded to develop efficient drainage systems. Beyond reconciling previously disconnected observations of modern and ancient ice streams into a single lifecycle, the modelling suggests that tunnel valley development may be crucial in stabilising portions of ice sheets during periods of climate change.

Groundwater Flow Under a Paleo‐Ice Stream of the Scandinavian Ice Sheet and Its Implications for the Formation of Stargard Drumlin Field, NW Poland

“…Subglacial processes (Clarke, ) control the dynamic behavior of ice streams, arteries of fast‐flowing ice which are important components of both contemporary and past glacial systems discharging disproportionally high volumes of ice and contributing to substantial sediment redistribution (Bennett, ; Stokes & Clark, ). Location and evolution of ice streams have been linked to subglacial parameters such as topography (Fransner et al, ; Hermanowski, ; Kessler et al, ; Margold et al, ; Rignot et al, ; Ross et al, ; Rychel & Morawski, ), geology (Anandakrishnan et al, ; Clark & Stokes, ; Peters et al, ; Rattas & Piotrowski, ; Studinger et al, ), hydrology (Bell et al, ; Christoffersen et al, ; Greenwood et al, ; Lelandais et al, ; Vaughan et al, ; Winsborrow et al, ), and thermal regimes (Bougamont et al, ; Christoffersen & Tulaczyk, , ). The impact of these parameters on ice flow is, through a series of feedbacks, coupled with glacial meltwater (Bougamont et al, ; Christoffersen et al, ; Clason et al, ; Gudlaugsson et al, ; Winberry et al, ), which feeds the subglacial groundwater system.…”