MAJOR OCEAN CURRENTS
Learning Objective:
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Identify the major ocean currents and their
locations, and recognize their effects on the weather.
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The major ocean currents are established and
maintained by the stresses exerted by the prevailing winds. Thus, the oceanic
circulation pattern roughly corresponds to Earth’satmospheric
circulation pattern. Since the air
circulation over the oceans in the middle latitudes is chiefly anticyclonic
(more pronounced in the Southern Hemisphere than in the Northern
Hemisphere), the oceanic circulation is
more or less the same.
At higher latitudes, where the windflow is principally
cyclonic, the oceanic circulation follows this pattern, although not as closely
as the anticyclonic pattern of the middle latitudes.
In regions of pronounced monsoonal flow, the monsoon
winds control the currents. The general distribution of ocean currents is as
follows:
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At middle (below 40° lat.) and low latitudes,
warm currents flow poleward along the eastern coasts of continents and cold
currents flow equatorward along the western coasts. This
is true in both hemispheres.
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In the Northern Hemisphere at high latitudes, cold
currents flow equatorward along the east coasts of continents, and warm
currents flow poleward along the western coasts.
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In monsoonal regions, ocean currents vary with the
seasons, and irregular coastlines can cause deviations in the general
distribution of ocean currents.
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The oceanic circulation pattern acts to transport heat
from one latitude belt to another in a manner similar to the heat transported by
the primary circulation of the atmosphere.  The
cold
waters of the Arctic and Antarctic move equatorward toward warmer water, while
the warm waters of the lower latitudes move poleward. The effect this
circulation pattern has on climate can be seen in
the comparatively mild climate that exists in the area of northwest Europe. Even
in winter, Norwegian ports along the Atlantic are ice-free most of the time.
This is due to the effect of the warm ocean current
that sweeps (si estende) northward along the Norwegian coast. In contrast,
a cold ocean current flows equatorward along the coast of California and
is a major reason that cities such as San Francisco experience relatively cool
summer temperatures. Figure 1-1-3 shows the surface currents of the oceans
during February and March.
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