The influence of subglacial hydrology on the flow of Kamb Ice Stream, West Antarctica

Abstract

[1] Ice streams on the Siple Coast, West Antarctica, have a complex history of flow because their basal motion is governed by time-varying basal conditions. Although the mechanical interaction between ice and till is well established, very little is known about the potential effect of regionally scaled water transport in a basal water system, which has only recently become apparent. To investigate the combined effect of hydrological and mechanical processes, we developed the Hydrology, Ice and Till model, in which ice flow is coupled to a Coulomb-plastic till layer and a basal water system consisting of discrete conduits. When the model is applied to Kamb Ice Stream (KIS), results confirm that it is capable of oscillating between fast and stagnant modes of flow. We show that when subglacial conduits are disregarded or do not extend to the grounding line, the oscillatory behavior of the ice stream is governed by the basal thermal regime. When conduits extend to the grounding line, the modelled ice stream oscillation period is increased, peak speeds are reduced, and oscillations may ultimately cease if the volume of water supplied is sufficiently high. Three different hydrological states characterize the behavioral patterns of ice flow and these states are distinguished by conditions at the grounding line. Modelled ice stream velocities were found to oscillate with fast and slow periods typically lasting a few hundred years, although varying according to hydrological activity. Our results indicate that KIS could reactivate this century, given its hydrological setting and~170 years of stagnation.Citation: van der Wel, N., P. Christoffersen, and M.

Modelling water flow under glaciers and ice sheets

“…Any model striving for broad applicability will have to treat polythermal bed conditions [188,206,214], a complication often neglected but potentially important for both drainage and ice dynamics [219,220]. In addition to a thermal patchwork at the glacier bed, direct observations of subglacial conditions (e.g.…”

“…[78,214]). Models that do treat hydrology have been developed for the Siple Coast ice streams, which are underlain by thick saturated sediments and lack strong topographic controls.…”

Importance of basal processes in simulations of a surging Svalbard outlet glacier

“…HIRHAM5 is based on the Undén et al (2002) and ECHAM5 models (Roeckner et al, 2003), combining the dynamics of the former model with the physical parameterisation schemes of the latter. The physics of the model have been supplemented with a surface snow scheme and SMB calculation for glaciers Rae et al, 2012).…”

“…Van Pelt and Oerlemans (2012) used a simple diffusion relation to simulate evolution of till water content and were able to demonstrate, for a plastic till (some of their simulations also included a small linearly viscous component), both lowfrequency oscillations (driven by changes in temperature distribution) and high-frequency oscillations (driven by changes in till water distribution) in an idealised outlet glacier, with till strength being an important factor governing possible oscillatory behaviour. van der Wel et al (2013) used a plastic till model with a hydrology model that incorporates representation of channelised flow at the ice-till interface to demonstrate the important control that connectivity through to the grounding line exerts on upstream sliding.…”

Stochastic ice stream dynamics

“…If, instead, ice is in direct contact with bedrock, the lubrication provided by water at the ice−rock interface controls the rate at which ice slips over the bed (25). Water transport and ponding along ice stream beds have been also observed (30)(31)(32)(33), and model studies (34)(35)(36)(37)(38)(39)) also point to the subglacial drainage system as a control on the spatial and temporal dynamics of ice streams.…”