Page 202 - (DK) Ocean - The Definitive Visual Guide

200 POLAR OCEANS

Polar Ocean Circulation

THE ARCTIC AND SOUTHERN OCEANS each have their own unique patterns
CIRCULATION AND FEEDING
of water flow, which link in with the rest of the global ocean circulation. The Southern Ocean meets warmer water
These flows are driven partly by wind and partly by various factors that at the Antarctic Convergence, creating a
biologically rich feeding area for whales,
influence the temperature and salinity of the surface waters in these including these humpbacks.
oceans—including seasonal variations in air temperature and sea ice
coverage, and large inflows of fresh water from rivers. Although driven by
similar influences, the significantly different water-flow patterns of these
two oceans are largely due to the fact that the Arctic Ocean is encircled
by land, whereas the Southern Ocean surrounds a frozen continent.

Arctic Surface Circulation
The upper 170 ft (50 m) of the Arctic Ocean is affected
by currents that keep it in constant motion. There are two
main components to this circulation (see p.424–25).
In a large area north of Alaska, there is a slow, circular
motion of water called the Beaufort Gyre. This
clockwise movement is wind-generated and
completes one rotation every four years. The
second component, the Transpolar Current,
is driven by a vast quantity of water
discharged into the Arctic Ocean
from Siberian rivers.

MOUTH OF THE LENA RIVER
The Lena flows across Siberia
and discharges 100 cubic miles
(420 cubic km) of water into
the Arctic Ocean every year.

OCEAN ENVIRONMENTS