Pressure ridge (ice)

A pressure ridge is a long, linear pile of broken sea ice formed where floes in pack ice are pushed together in an ocean or coastal setting. Currents and winds drive the floes into one another, and the stress within the plane of the ice crumples the margins into a ridge made of angular blocks, mostly 20 to 40 centimetres thick and broken from thin, young ice. The part above the water is called the sail and the part below it the keel. Pressure ridges are the thickest features of sea ice and make up as much as 30 to 40 percent of the sea ice area and about half of its volume. Grounded ridges formed where fast ice meets drifting pack ice are called stamukhi, and a ridge may be first-year, second-year or multiyear depending on how many melt seasons it survives.