Beginning of Essay
Typically, the level of ocean water around the world is higher in the western Pacific and lower in the eastern, near the Western coast of South and North America. This is due primarily to the presence of easterly winds in the Pacific, which drag the surface water ....

Middle of Essay
.... the western South American coastline, and cold waters of the Pacific rise and push westward. However, during an El Nino year, upwelling is suppressed and as a result, the thermocline is lower than normal. Finally, thermocline rises in the west, making upwelling easier and water colder. Air pressures at sea level in the South Pacific seesaw back and forth between two distinct patterns. In the high index phase, also called "Southern Oscillation", pressure is higher near and to the east of Tahiti than farther to the west near Darwin. The east-west pressure difference along the equator causes the surface air to flow westward. When the atmosphere switche ....