Geography Reference
In-Depth Information
Figure 9-7: A
generalized geo-
graphy of ocean
surface currents.
After leaving the Tropics, the reverse starts to happen: the currents radiate more heat than they gain
— but slowly for the reasons you read about in the previous section concerning the ability of water
to store and retain heat. Thus, the currents remain comparatively warm longer after they have left the
tropics. The Gulf Stream, for example, is a warm-water current that moves up the Eastern coast of
the United States and then becomes the North Atlantic Current (see Figure 9-7). Although it loses a
fair amount of heat as it moves eastward across the mid-Atlantic, the North Atlantic Current reaches
Europe with a considerable amount of stored heat remaining. As it continues to radiate that heat, it
contributes to the climate of Northwestern Europe a degree of warmth that is unusual for those latit-
udes, and also abundant rainfall.
Take a look at an example of an area that is affected by the North Atlantic Current. Bergen, Norway
(Lat. 61°N) has an annual temperature of 45° F and receives 77 inches of precipitation per year.
Compare that to Churchill, Manitoba (Lat. 58° N), which, as mentioned earlier in the chapter, has
an annual average temperature of 19° F and only 15 inches annual precipitation. Bergen is signific-
antly warmer — despite its high latitude — and much wetter. The difference is partly a matter of
Churchill's continentality, and partly a matter of the relatively warm current that sideswipes Bergen.
But the Gulf Stream-North Atlantic Current is not yet finished. After impacting Western Europe, the
current turns south towards the equator, now as the Canaries Current, to complete its circulatory
cycle. By that time, however, it has lost most of the heat it once had. As a result, the Canaries Current
that sideswipes Northwest Africa is quite cool.
Casablanca, Morocco (Lat. 33° N), for example, has an annual average temperature of 63° F, which
is comparatively cool for a country on the fringe of the Saharan realm. It also receives only 17 inches
of precipitation per year. That is a paltry sum compared to the 77 inches that the same circulatory
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