Motion of Water. In the Ocean There

¶ … motion of water. In the Ocean there are three major types of currents; Tidal, Coastal, and Surface Ocean.

Coastal currents are movements of water that are located near the coast and are influenced by wind, waves and land formations. Surface Ocean currents are currents that are located throughout the oceans, involve much more complex influences like global wind systems, the spin of the earth, salinity, and water temperatures.

Normally wind patterns on the earth follow a cycle of circulation between the equator and the poles. But because the earth rotates on it's axis, these normally north and south wind patterns develop a slight curve, called the Coriolis effect. In the northern hemisphere this effect causes the winds to curve to the right, in the southern hemisphere, to the left. As the winds blow on the surface of the oceans, it drags the surface of the water in the same direction as the winds. This causes the major surface currents to follow flow in a circular pattern, clockwise in the northern hemisphere and counter clockwise in the southern.

D. The Coriolis effect creates a circular current in the worlds oceans, but it is not the only force influencing these currents. The wind can cause surface currents, but the mechanism behind the circular system is called the global conveyor belt. When warm water is dragged by wind currents to the polar regions, it becomes cold, and cold water sinks. As it sinks, it comes under the influence of other deep water currents which flow in the opposite direction, toward the equator. Currents at deeper levels flow in opposite directions because of the Ekman Spiral; an side effect of the Coriolis effect. The spin of the earth causes the flow of water either slightly to the right, or the left; but as one goes deeper into the ocean, this effect becomes greater and greater until the water is actually moving in the opposite direction.

E. Traditionally ocean current have been measured by the simplest of means; usually an observer and two stationary points. An object, called a "drifter," would be dropped into the water, and the time it took to travel from one point to the other was measured. The observer could then calculate the velocity of the current. While today's seafarers use the same general principles, the technology surrounding it has improved greatly. Modern buoys, equipped with global positioning satellite technology, are used as "drifters" to be carried along in ocean currents and relay their position back to a satellite. This information is then compiled in a computer system which compiles and analyzes the data.

PART II

5. San Francisco Station Number 9414290

Date: 5/8/2011

High Tide: 1.784 Meters @ 09:51 GMT (9:51 PM local time)

Low Tide: -0.086 Meters @ 16:06 GMT (4:06 AM local time)

Tidal Range: 1.698 Meters

6. Prediction for 5/9/2011

A. The predicted high tide is to take place at 09:51 GMT, and be 1.67 meters. The low tide is to take place at 16:42 GMT, and be -0.16 meters. This is not the same time as 5/8/2011, primarily due to the moon's influence on the tides and the fact that the moon will not be in the same position relative to the earth two days in a row.

B. On 5/9/2011 the actual high tide was 1.702 meters, .035 meters higher than predicted, while the actual low tide was -0.035 meters, 0.125 meters less than predicted. Meaning the tide was supposed to go to - 0.160 meters, but only dropped to -0.035 meters. This could be explained by wind patterns pushing water toward shoe, increasing water levels during high tide, but reverse winds could push the water away from shore during low tide, making low tide even lower. Increased and decreased movements of coastal currents can also keep water moving away from the shore, decreasing tide levels, or they could keep more water available for use in tides, increasing tide levels.