Page 193 - (DK) Ocean - The Definitive Visual Guide

THE TWO POLAR OCEANS are the Arctic
Ocean in the Northern Hemisphere and the

Southern Ocean, which surrounds the

continent of Antarctica, in the Southern
Hemisphere. They differ from other oceans

in several respects, not least in the sheer

quantity of ice that floats on them. This

includes sea ice, which is frozen seawater,

and icebergs and ice shelves, which are
frozen fresh water. The polar oceans contain

fewer temperature layers than other

oceans, being uniformly cold, and they have
different circulation patterns, which are

partly wind-driven but also influenced by

such factors as river inflow (in the Arctic

Ocean) and sea-ice formation. The edges of

the sea ice are biologically productive zones
where plankton blooms occur in summer,

attracting many fish, birds, and mammals.

POLAR OCEANS

PENGUINS UNDER THE ICE
These emperor penguins are swimming in
a break in the sea ice off the coast of
Antarctica. They can dive to 2,000 ft (600 m),
staying down for up to 20 minutes.