Meltwater generation in ice stream shear margins: case study in Antarctic ice streams

Liquid water within glacier ice and at the glacier beds exerts a significant control on ice flow and glacier stability through a number of processes, including altering the rheology of the ice and lubricating the bed. Some of this water is generated as melt from regions of rapid deformation, including shear margins, due to heating by viscous dissipation. However, how much meltwater is generated and drained from shear margins remains unclear. Here, we apply a model that describes the evolution of ice temperature, melting, and water transport within deforming ice to estimate the flux of meltwater from shear margins in glaciers. We estimate the flux of meltwater from temperate ice zones in three Antarctic regions: Bindschadler and MacAyeal Ice Streams, Pine Island Glacier, and Byrd Glacier. We show that the flux of meltwater from shear margins in these regions may be as significant as the meltwater produced by frictional heating at the bed, with average fluxes of similar to 0.005-0.1 m yr-1. This contribution of shear heating to meltwater flux at the bed may thus affect both the rheology of the ice as well as sliding at the bed, both key controls on fast ice flow.

Automated summary

Liquid water within glacier ice and at the glacier beds plays a significant role in ice flow and stability. Meltwater from regions of rapid deformation, including shear margins, can affect the rheology of the ice and lubricate the bed. This study estimates the flux of meltwater from shear margins in three Antarctic regions and finds that it can be as significant as meltwater produced by frictional heating at the bed.