Environmental Engineering Reference
In-Depth Information
For the Antarctic the 10° C summer isotherm encircles the whole of continental
Antarctica and also includes the tip of South America, Tierra del Fuego, and many
islands in the southern ocean, including the Falkland Islands and South Georgia. It seems
to separate quite well those islands which are treeless from those which are not. However,
the Antarctic is so much dominated by the southern ocean, and is so obviously a marine
environment rather than a terrestrial one, that many authorities prefer to use a maritime
boundary. The most generally accepted is the Antarctic convergence, a sharp boundary
between Antarctic surface water and slightly warmer and more saline subantarctic surface
water. It marks the point where colder Antarctic water moving north and east sinks below
subantarctic water moving east and slightly southwards. It varies between latitudes 45° S
and 62° S, being farther south in the Pacific than in the Atlantic, and in the summer than
in the winter (Figure 24.2). The equivalent Arctic maritime boundary is between cold,
less dense surface water from the Arctic Ocean and warmer, more saline water from the
south. Again the contrasts in temperature, density and salinity are reflected in very real
ecological differences between the water masses, with distinct communities of plants and
animals. Figure 24.1 shows how the Arctic maritime boundary is pushed to above 80° N
and to the east of Novaya Zemlya by the North Atlantic Drift. Warm Pacific water also
extends up the west coast of North America and penetrates the Bering Strait to go from
Wrangel Island almost to Prince Patrick Island in the east.
VEGETATION AND SOILS IN HIGH LATITUDES
Vegetation is only one component of ecosystems, but special importance is attached to it,
as it provides the basis of natural productivity, fixes carbon by photosynthesis,
Figure 24.2
Important physical limits in the Antarctic: the 10
° C January isotherm, the Antarctic convergence and the
northern limit of pack ice in winter.
