Critical dike width required to sustain flow to the surface through the cold SP ice sheet (red line). Turbulent and laminar flow fields are indicated for dikes wider than the critical value. The line separating laminar flow from turbulent flow is determined by the Reynolds number, which is given by Re = (2a)w/ν for a dike of width 2a, the mean fluid velocity is w, and ν is the fluid’s kinematic viscosity. The critical Reynolds number for the laminar-to-turbulent transition in a dike is ~1800.