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 only found in Antarctica,
Greenland and Canada. The boundary between the floating ice
shelf and the grounded (resting on bedrock) ice that feeds it is
called the grounding line. The thickness of ice shelves ranges
from about 100 to 1000 metres. Ice shelves are principally
driven by gravity-driven pressure from the grounded ice  That
flow continually moves ice from the grounding line to the
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. Ice may also accrete onto the underside
of the shelf. The density contrast