I found this bit from Wikipedia:
Recently,
glaciologists have observed unexpected ice-shelf events, such as complete disintegration of some small ice shelves. For example, two sections of Antarctica's
Larsen Ice Shelf broke apart into hundreds of unusually small fragments (100's of meters wide or less) in 1995 and 2002. The breakup events are linked to climate change in the region, although there is not complete agreement about the most important causative process. The leading ideas involve enhanced ice fracturing due to surface meltwater and enhanced bottom melting due to warmer ocean water circulating under the floating ice.
More info for wallyj:
An
ice shelf is a thick, 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,
Greenland and
Canada only. The boundary between floating ice shelf and the grounded (resting on bedrock) 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 throughout the
Arctic Ocean. It also is found in the
Southern Ocean around the continent of Antarctica.
Ice shelves flow by gravity-driven horizontal spreading on the ocean surface. That flow continually moves ice from the grounding line to seaward front of the shelf. The primary mechanism of mass loss from ice shelves is
iceberg calving, in which a chunk 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 accumulation on the upper surface and melting from the lower surface are also important to the
mass balance of an ice shelf.
This is what an ice shelf looks like.
