Forms of grease ice ridges on the south coast of the Baltic Sea

The paper presents the forms of grounded grease ice ridges as well as hydrological, meteorological and physiographic conditions of their occurrence on the south coast of the Baltic Sea. The author used results of observations and measurements performed during hiking expeditions and analyzed profiles and photographs showing the morphology of grease ice ridges which occur along the coast and are usually several meters wide and 1-3 m high. Their windward slopes are very steep, usually concave, with abrasion niches and ice cornices formed by waves. The leeward slopes are gentle (20-30°) and coincident with the angle of the natural slip (angle of slide) of the grease ice, slush and shuga tossed by waves. The major factor leading to grease piling is the movement of waves generated by a strong onshore (NW, N, NE) wind. Such wind conditions occur mainly when a low-pressure area extends to the E, SE and/or S of the southern Baltic, and a high-pressure area – to the W, NW and/or N.