Ice shelf

An ice shelf is a large floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are found in Antarctica and the Arctic (Greenland, Northern Canada, and the Russian Arctic). The boundary between the floating ice shelf and the anchor ice (resting on bedrock) that feeds it is the grounding line. The thickness of ice shelves can range from about 100 m (330 ft) to 1,000 m (3,300 ft). The world's largest ice shelves are the Ross Ice Shelf and the Filchner-Ronne Ice Shelf in Antarctica. When a large piece of an ice shelf breaks off, this can lead to the formation of an iceberg (which is a piece of freshwater ice more than 15 m long). This process is also called ice calving.

The movement of ice shelves is principally driven by gravity-induced pressure from the grounded ice. That flow continually moves ice from the grounding line to the seaward front of the shelf. Typically, a shelf front will extend forward for years or decades between major calving events (calving is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse). Snow accumulation on the upper surface and melting from the lower surface are also important to the mass balance of an ice shelf. Ice may also accrete onto the underside of the shelf.

The effects of climate change are visible in the changes to the cryosphere, such as reduction in sea ice and ice sheets, and disruption of ice shelves. In the last several decades, glaciologists have observed consistent decreases in ice shelf extent through melt, calving, and complete disintegration of some shelves. Well studied examples include disruptions of the Thwaites Ice Shelf, Larsen Ice Shelf, Filchner–Ronne Ice Shelf (all three in the Antarctic) and the disruption of the Ellesmere Ice Shelf in the Arctic.