ShareEarth's Energy - How Does Spinning Affect Wind?
If
Earth did not rotate on its axis, winds would blow from the north toward
the south, and south toward the north. A straight line as drawn at the
left models this kind of wind direction.
You know, however, that Earth does rotate. This rotation causes a difference from the line as drawn in this video.
Because Earth rotates on its axis from west towards the east, air near the surface from the tropics is moved toward a westerly direction (toward the right as it is often called) in the northern hemisphere.
Notice the difference between the lines drawn when the globe did not move (shown with arrow heads) and the lines which were drawn as Earth rotated.
T
he
Coriolis Effect also causes ocean surface currents to be deflected to
the right of the winds. At the equator, there is no Coriolis Effect so
there is very little to no deflection. At other latitudes, each layer
of water (depth) is set into motion by the Coriolis Effect. Each layer
moves at different velocities and moves to the right until (if you were
to look from above), a spiral shape of ocean currents would form. View this video modeling the effect
of the Coriolis Effect.
As seen in the diagram at the right, adding each of these directions together produces a net current of flow which is perpendicular to the wind (within about the top 100 meters of ocean water). This phenomenon causes currents in the northern hemisphere to move in a clockwise direction and a counterclockwise direction in the southern hemisphere. If there were no continents or island land masses, each of the ocean currents would have either an easterly or westerly flow. However, landmasses interupt the flow of ocean currents creating closed circular current systems called gyres. The five major gyres are; the North Pacific Gyre, the South Pacific Gyre, the North Atlantic Gyre, the South Atlantic Gyre, and the Indian Ocean Gyre. The parts of all gyres closest to the equator move toward the west as equatorial currents. As these gyres encounter landmasses, they are deflected toward the poles. These gyres carry warm ocean water toward cooler regions, affecting not only ocean water, but the air temperatures as well. These warm currents such as the Gulf Stream, and the Japanese Current help to moderate the weather, keeping air temperatures warmer. A prime example of this can be found along the western coasts of Great Britian. Warm Gulf Stream Water from the Gulf of Mexico helps to keep the climate more moderate. Compare the same latitude to that of central Canada.
In addition to surface currents, water also moves vertically as deeper water rises toward shallower depths. This is referred to as Upwelling. Upwelling can occur during a La Nina event where warmer surface waters and air temperatures are blown from the western coasts of South America toward Indonesia and Australia. Deeper water from below rises toward the surface, replacing the horizontally moving water. The upwelling water is cooler and nutrient rich, causing a decrease in air temperatures near the surface.
Using the information given above, label on a world map, the five gyres. Also, label the following currents; South equatorial current, the North Equatorial Current, the North Pacific current, the California Current, the EAC, the South Equatorial Current, the Gulf Stream, the Canary current, the Peru Current, the North Atlantic Current, and the Alaska Current.
