A boundary layer model for ice stream margins

Haseloff, Marianne; Schoof, Christian; Gagliardini, Olivier

doi:10.1017/jfm.2015.503

Cited by 28 publications

(99 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, if we instead considered a flow line through the shear margin (though this in conflict with other assumptions made in model formulation), then lateral shear heating is non-negligible (10 %). Nonetheless, in order to draw definitive conclusions about specific ice streams, more complete 3-D ice-stream modeling is needed, which takes into account variations in bed properties simulated in this study and also details not captured by a flow-line model, such as fully dynamic ice shelf buttressing, cross-stream variations in basal topography, lateral advection and shear margin migration (Haseloff et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

Persistence and variability of ice-stream grounding lines on retrograde bed slopes

2016

View full text Add to dashboard Cite

Abstract. In many ice streams, basal resistance varies in space and time due to the dynamically evolving properties of subglacial till. These variations can cause internally generated oscillations in ice-stream flow. However, the potential for such variations in basal properties is not considered by conventional theories of grounding-line stability on retrograde bed slopes, which assume that bed properties are static in time. Using a flow-line model, we show how internally generated, transient variations in ice-stream state interact with retrograde bed slopes. In contrast to predictions from the theory of the marine ice-sheet instability, our simulated grounding line is able to persist and reverse direction of migration on a retrograde bed when undergoing oscillations in the grounding-line position. In turn, the presence of a retrograde bed may also suppress or reduce the amplitude of internal oscillations in ice-stream state. We explore the physical mechanisms responsible for these behaviors and discuss the implications for observed grounding-line migration in West Antarctica.

show abstract

Section: Discussionmentioning

confidence: 99%

Persistence and variability of ice-stream grounding lines on retrograde bed slopes

2016

View full text Add to dashboard Cite

show abstract

“…Since we only model processes in the y-z plane, we cannot model the emergence of ice streams and ice ridges, as, for example, in Kyrke-Smith et al (2014). Instead, we assume the existence of an ice stream and adopt the following approximate profile for the ice thickness H (Haseloff et al, 2015):…”

Section: The Modelmentioning

confidence: 99%

“…Models linking the basal yield stress to physical processes can be divided into two categories. In the first, τ c is a function of temperature, in which case the transition from slip to no slip is linked to a transition from a temperate to a frozen bed (Haseloff et al, , ; Jacobson & Raymond, ; Schoof, ). In the second, τ c is a function of the water pressure in the subglacial sediment, in which case the transition from slip to no slip is hydrologically controlled (Elsworth & Suckale, ; Kyrke‐Smith et al, , ; Meyer et al, ; Perol et al, ; Platt et al, ).…”

Section: Introductionmentioning

confidence: 99%

Englacial Pore Water Localizes Shear in Temperate Ice Stream Margins

2019

Self Cite

View full text Add to dashboard Cite

The margins of fast‐moving ice streams are characterized by steep velocity gradients. Some of these gradients cannot be explained by a temperature‐dependent viscosity alone. Laboratory data suggest that water in the ice‐grain matrix decreases the ice viscosity; we propose that this causes the strong localization of shear in temperate ice stream margins. However, the magnitude of weakening and its consequences for ice stream dynamics are poorly understood. Here we investigate how the coupling between temperate ice properties, ice mechanics, and drainage of melt water from the ice stream margin alters the dynamics of ice streams. We consider the steady‐state ice flow, temperature, water content, and subglacial water drainage in an ice stream cross section. Temperate ice dynamics are modeled as a two‐phase flow, with gravity‐driven water transport in the pores of a viscously compacting and deforming ice matrix. We find that the dependence of ice viscosity on meltwater content focuses the temperate ice region and steepens the velocity gradients in the ice stream margin. It provides a possible explanation for the steep velocity gradients observed in some ice stream shear margins. This localizes heat dissipation there, which in turn increases the amount of meltwater delivered to the ice stream bed. This process is controlled by the permeability of the temperate ice and the sensitivity of ice viscosity to meltwater content, both of which are poorly constrained properties.

show abstract

“…The hydrology includes thin-film and channel drainage systems (after Creyts & Schoof, 2009;Hewitt, 2011Hewitt, , 2013. R-channel = Röthlisberger channel. ice streams rely in part on the inflow of ice from the surrounding cold ridges, suppressing the formation of temperate ice (Haseloff et al, 2015;Suckale et al, 2014). Thus, the existence and thickness of a temperate zone must vary along the margin (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

A Model for the Downstream Evolution of Temperate Ice and Subglacial Hydrology Along Ice Stream Shear Margins

et al. 2018

View full text Add to dashboard Cite

Antarctic mass balance and contribution to sea level rise are dominated by the flow of ice through narrow conduits called ice streams. These regions of relatively fast flow drain over 90% of the ice sheet and generate significant amounts of frictional heat at the ice stream margins where there is a transition to slow flow in the ridge. This heat can generate temperate ice and a sharp transition in flow speed between the stream and the ridge. Within zones of temperate ice, meltwater is produced and drains to the bed. Here we model the downstream development of a temperate zone along an ice stream shear margin and the flow of meltwater through temperate ice into a subglacial hydrologic system. The hydrology sets the basal effective pressure, defined as the difference between ice overburden and water pressure. Using the southern shear margin of Bindschadler Ice Stream as a case study, our model results indicate an abrupt transition from a distributed to channelized hydrologic system within a few ice thicknesses of the point where the temperate zone initiates. This transition leads to a strengthening of the till due to reduced pore pressure because the water pressure in the channel is lower than in the distributed system, a potential mechanism by which hydrology can prevent lateral migration of shear margins.

show abstract

A boundary layer model for ice stream margins

Cited by 28 publications

References 54 publications

Persistence and variability of ice-stream grounding lines on retrograde bed slopes

Persistence and variability of ice-stream grounding lines on retrograde bed slopes

Englacial Pore Water Localizes Shear in Temperate Ice Stream Margins

A Model for the Downstream Evolution of Temperate Ice and Subglacial Hydrology Along Ice Stream Shear Margins

Contact Info

Product

Resources

About