Sea-level projections depend sensitively on the parameterization used for basal slip in glacier flow models. During slip over rock-beds. ice-bed separation increases with slip velocity and basal water pressure. We present a method for using these variables and measured bed topography to estimate the average bed slope in contact with ice. https://www.ngetikin.com/flash-choice-1-Gallon-Roll-Cote-High-Performance-Moisture-Vapor-Barrier-Coating-and-Primer-limited-super/