| Summary: | Ice streams transport the majority of the ice lost to the ocean from the Antarctic Ice Sheet. In many cases these fast-flowing streams are bordered by nearly stagnant ice ridges that supply cold ice through lateral advection. The interplay between concentrated viscous heating in shear margins and advective cooling from ridge influx and surface accumulation determines margin ice temperatures, which determine ice viscosity, hence exerting a primary control on peak strain rates and ice stream velocity. A significant meltwater supply, which has potential to lubricate the ice stream bed, comes from basal friction and also from viscous dissipation within temperate zones that are predicted to develop within some shear margins. The presence of temperate ice in the shear margin also alters the melt distribution to the bed, and has been invoked as a control on ice stream widening. Here, we present a quasi-three-dimensional, steady-state ice stream model that includes both temperature-dependent ice rheology, and lateral and vertical advection. Through the study of an idealized ice stream we identify key parameters, and examine how varying conditions over realistic values alters ice stream behavior. We then consider a specific, natural system, Bindschadler Ice Stream, testing our model against measured data and previous studies. We also utilize predicted future climate conditions from CMIP5 and find a warming polar region could increase shear melting within Bindschadler, if steady-state is reached, by up to 750%, corresponding to a near tripling in total meltwater supply to the subglacial system. The expanded temperate ice zone at Bindschadler is also predicted to result in an increase to centerline velocity of up to 200%.
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