Resistance on a ship penetrating a sea ice ridge is a key design parameter of ice breaking ships. The resistance of a ship in an unconsolidated ridge has been studied by using a three dimensional discrete element method. Ridges of equal thickness but different widths were used and it was observed that the ridge width has a major effect on the ridge resistance: The ridge resistance is increasing with increasing ridge width, until the ridge width is of the same order as the ship length. The ridge resistance was decomposed into a frictional force and a deformation force. The deformation force is due to the ridge deformation by the ship bow and it was shown that the deformation force is related with the mass of ice blocks accelerated by and moving with the ship.