Ocean Dynamics - AP Environmental Science

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Question

Why do storms in the Southern hemisphere swirl clockwise, while storms in the Northern hemisphere swirl counterclockwise?

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Answer

Physics describes the Coriolis effect as "the deflection of a moving object due to a rotating reference frame." When the motion is clockwise, the deflection is to the left. When motion is counterclockwise, the deflection is to the right. Put into context: Earth's major wind patterns dictate ocean currents (the object) for the most part—however, the rotation of the Earth deflects surface currents at an angle of about 45 degrees to the wind. The result is a rightward deflection in the Northern hemisphere, and a leftward deflection in the Southern hemisphere.

Eckman transport is the change in wind direction correlating to altitude due to the varying effect of surface friction. Thermohaline circulation is the pattern by which the density of water increases as it becomes colder and saltier; thus it sinks at high latitudes and is replaced by warmer water from the tropics flowing north. This is a key mechanism that regulates Earth's climate. While different hemispheres experience different amounts of heat/light, this is not the reason for the phenomenon described in the question. Finally, ocean currents do not have the ability to dictate storm currents.

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