Unit 9: Southern Oscillation

A changing pattern of reversing surface air pressure between the Eastern and Western tropical pacific regions.

• Trade winds blow WEST across pacific, pushing warm surface water westward from the coasts of South America to Australia • As the water most WEST it heats up from exposure to Solar Radiation • Difference in heating between the waters in the WEST and EAST causes a thermocline to form. • Upwelling occurs in Eastern pacific to replace waters (Nutrient rich, good fishing) • Warm water in Western pacific, increases evaporation, therefore increased cloud formation, then rainfall. • Dry air that falls from Western pacific to EAstern results in little rainfall in Eastern tropical pacific.

• Trade winds weaken, and sometimes even reversew allowing warmer waters from the Western pacific to flow toward the East. • Therefore sea level flattens. • Warm water builds up off the coast of South America, increasing the temperature of the water. • Upwelling decreases, causing death of fish. • Heavy rainfall in peru, as warm waters evaporate and cause formation of clouds,. • Drought over Indonesia and Australia, as trade winds no longer bring moist air over which contributes to cloud formation.

• Trade winds strengthen, blowing even more warm water to the Western Pacific. • Causes increased upwelling in Eastern Pacific and lower surface sea temperatures.