Floating mass of ice that has broken from the seaward end of a glacier or a polar ice sheet.
Icebergs are typically found in open seas, especially around Greenland and Antarctica. They form mostly during each hemisphere's spring and summer, when warmer weather increases the rate of calving (separation) of icebergs at the boundaries of the Greenland and Antarctic ice sheets and smaller outlying glaciers. In the Northern Hemisphere, about 10,000 icebergs are produced each year from the Greenland glaciers, and an average of 375 flow into the North Atlantic shipping lanes, where they are a hazard to navigation, especially because only about 10% of an iceberg is exposed above the surface of the sea.