The ice flow at the margins of the West Antarctic Ice Sheet (WAIS) is moderated by large ice shelves. Their buttressing effect substantially controls the mass balance of the WAIS and thus its contribution to sea level rise. The stability of these ice shelves results from the balance of mass gain by accumulation and ice flow from the adjacent ice sheet and mass loss by calving and basal melting due to the ocean heat flux. Recent results of ocean circulation models indicate that warm circumpolar water of the Southern Ocean may override the submarine slope front of the Antarctic Continent and boost basal ice shelf melting. In particular, simulations demonstrate the redirection of a warm coastal current into the Filchner Trough and underneath the Filchner-Ronne Ice Shelf (FRIS) within the next decades. In coupled simulations with a finite elements ocean model and a three-dimensional thermomechanical ice flow model we reveal that the consequent thinning of the FRIS would lead to an extensive grounding line retreat associated with a vast mass loss of the WAIS. In a subsequent study, we focus on the ice streams which are draining into the FRIS and dominating the mass transport from grounded to floating ice. For a better representation of these fast-flowing ice features we expand the above ice flow model by the incorporation of local processes at the ice base. There, sediment deformation and lubrication by subglacial hydrology locally allow high basal sliding rates and thus create the precondition for the development of ice streams. A parametrization of basal sliding properties by the simulated basal melt water fluxes allows us to depict velocity and locations of observed ice streams in the catchment of the FRIS more realistically. We present first results of this advanced ice-flow modeling approach, anticipating an even larger response of the AIS to increased sub-shelf melting rates in future coupled simulations.