Ice shelf

An ice shelf is a broad, balanced platform of ice that forms where a glacier or ice sheet flows down to a shoreline and onto the ocean surface, typically in Antarctica or Greenland. The border between floating ice shelf and the grounded ice that feeds it is called the grounding line. When the grounding line retreats inland, water is added to the ocean and sea level rises.

In contrast, sea ice is formed on water, is much thinner, and forms all through the Arctic Ocean. It also is bring into being in the Southern Ocean around the continent of Antarctica.

Ice shelves flow by gravity-driven straight distribution on the ocean surface. That flow frequently moves ice from the grounding line to seaward front of the shelf. The main mechanism of mass loss from ice shelves is iceberg calving, in which a large piece of ice breaks off from the seaward front of the shelf. Typically, a shelf front will extend forward for years or decades between major calving events. Snow buildup on the upper surface and melting from the lower surface are also imperative to the mass balance of an ice shelf.

The thinness of modern-day ice shelves ranges from about 100 to 1000 meters. The thickness similarity between solid ice and liquid water means that only about 1/9 of the floating ice is above the ocean surface. The world's main ice shelves are the Ross Ice Shelf and the Filchner-Ronne Ice Shelf in Antarctica.