Page 195 - (DK) Ocean - The Definitive Visual Guide

ICE SHELVES 193

Surface and Interior Beneath the Ice Shelves

The upper surfaces of Antarctic ice shelves are inhospitable places. For Underneath the Antarctic ice shelves are extensive bodies
most of the year, cold air streams called katabatic winds blow down of water that are some of the least explored regions
from the Antarctic Ice Sheet and over the ice shelves. The surface of on Earth. Seawater is thought to circulate
the ice is not flat, but is shaped by the winds into a series of ridges and constantly here, caused partly by new ice
troughs, called sastrugi. These are formation underneath and around the
typically covered in a snow blanket. ice shelves. As new ice forms, it “rejects”
In some areas, the surface is littered salt, making the surrounding seawater
with rocks from the input glacier or denser. This causes the seawater to sink, and
glaciers, or even with material that helps drive the circulation. Recent attempts
has been carried upward from the have been made to explore these areas, using
sea floor by vertical movement. In robotic submarines to take measurements.
summer, small ponds form on some Little is known about the organisms that
ice shelves and provide a home for live here, although in 2005 a community LIFE UNDER THE ICE
Organisms such as starfish and
various types of microscopic of clams and bacterial mats was found on worms live in shallow water
organisms. Internally, an ice shelf the sea floor under the Larsen B Ice Shelf around the edge of Antarctica,
usually contains some tide-induced after it broke up (see p.487). and possibly under the ice shelves.
cracks and crevasses. melting zone
marine ice is
annually ice shelf
reforming found beneath SEAWATER
CAVE INSIDE AN ICE SHELF new ice fast ice sea level CIRCULATION
In summer, the internal cracks ice platelets A continuous circulation
rise as density
and crevasses in an ice shelf decreases of seawater is thought
may enlarge to form caves as to occur under large
some of the ice melts. ice shelves, driven by
low-salinity sea-ice formation on its
water undersurface and partial
melting at depth.
high-salinity water
grounding line
ice pump driven by
salt rejection OCEAN ENVIRONMENTS