OceanCirculation

= = flat =__**Ocean Currents**__=
 * Most Ocean Water Is Moved By The Great Ocean Conveyor Belt System.
 * Caused by Coriolis Effect, Temperatures, and Salt Density
 * Wind Patterns Drive Surface Currents. Surface Currents Cause Waves.
 * Surface Currents also cause GYRES- a rotational current of water that circles in a large area (fig 5.13 on pg 103 in textbook)
 * Land masses can impede (disrupt) the currents from forming a true circle.

//The Coriolis Effect On Ocean Currents// Just like with atmopsheric circulation, the Coriolis Effect moves water in a curved direction as it leaves the polar regions.
 * This means that surface currents move in a clockwise direction in the northern hemisphere and a counter-clockwise direction in the southern hemisphere.

//The Ocean Conveyor Belt Affects Vertical Ocean Mixing// As the Gulf Stream passes north through the Atlantic Ocean, it loses a lot of the water molecules to evaporation due to the heating of the water (the water is heated, the water molecules evaporate, form clouds, and this rain -and moderate temperature- is dumped on Europe). Once a significant amount of the water molecules have evaporated, the salt is left behind. This leaves salt in less water, which means the water that's left is more dense. This causes an intense sinking of the colder dense water to the bottom of the Pacific Ocean and this sudden drops allows for the running of the entire Ocean Conveyor Belt System.
 * Remember that water is at its densest point at 4 degrees Celsius. Below this temperature, the freezing process begins and water is typically expanding and stagnant.
 * Cold water is always saltier. It is the densest water in the ocean and is therefore likely to sink.
 * Warm water is less salty and therefore floats above the denser, colder water.
 * The Ocean Conveyor Belt Helps Control Global Climate
 * Without this constant water movement, warm temperatures would not reach areas that rely on them for sustaining life.
 * Without the conveyor, Europe would freeze and potentially go back into an ice age.
 * Excess freshwater entering the north Pacific could lead to disruption in the salt-freshwater mix, causing a change in density, and therefore a change in the current.

=__**El Nino Southern Oscillation Event (ENSO)**__ pg. 105= "Normally, westward-blowing trade winds restrict the warmest waters to the western Pacific near Australia. Every three to seven years, however, the trade winds weaken, and the warm mass of water expands eastward to South America, increasing surface temperatures in the East Pacific. Ocean currents, which normally flow westward in this area, slow down, stop altogether, or even reverse and go eastward. The name for this phenomenon, "El Nino", refers to Christ child because the warming usually reaches the fishing grounds off Peru just before Christmas. Most last from one to two years." = = =__**La Nina**__= La Nina is the opposite of El Nino. Surface waters become unnaturally cool and trade winds become unnaturally strong. La Nina occurs after an El Nino and is part of the El Nino cycle. Typically La Nina can cause wetter than normal winters, warmer weather in the southeast US, and drought in the southwest US. Hurricanes in the Atlantic are also more numerous and stronger during La Nina.
 * El Nino is caused by warmer-than-usual water currents reaching the West Coast of Peru, typically around mid-December. EL NINO AFFECTS THE TROPICAL PACIFIC OCEAN, ESP PERU.
 * Peruvian fisheries rely on __upwelling__ to bring nutrient-rich water to the surface, which draws fish to their fisheries.
 * During an El Nino year, the colder, nutrient-rich water is kept at a lower depth than normal and therefore does not draw fish to the surface or even to the area. Fish populations also decrease due to the lack of available nutrients.
 * Effects of El Nino can include
 * Decrease in fish populations
 * flooding in the North & South American west and droughts in other areas
 * reversal or complete halting of trade currents necessary for shipping routes.