Topic 4.9 El Nino and La Nina

Gyers

A huge circle of moving ocean water found above and below the equator due to global wind (clockwise in the Northern Hemisphere, counterclockwise in Southern Hemisphere).

Thermochaline Circulation

All of the oceans mix salt, nutrients and temperature depending on the direction of the winds.

Upwelling Zones

Areas of diverging and rising waters. Pushes nutrients and oxygen deprived water to the top. Areas of the ocean where cool, nutrient-rich water from deeper layers rises to the surface.

Effect of La Nina

Stronger upwelling & better fisheries in SA than normal Worse tornado activity in US & Hurricane activity in Atlantic Cooler, drier weather in Americas more precipitation, warmer, increased monsoons in SE Asia

Effects of El Nino

Suppressed upwelling & less productive fisheries in South America Warmer winter in much of North America Increased precipitation & flooding in Americas (W coast especially) Drought in Southeast Asia & Australia Decreased hurricane activity in Atlantic ocean Weakened monsoon activity in India & Southeast Asia.

What is the difference between El Nino y La Nina?

El Nino: Trade winds crossing the Pacific are weaker than normal. Results in less upwelling of cold water in the east. This means more less nutrients are available for fish. This pushes rainfall further inland. Peru and the southern US typically get more rainfall than usual. Australia and Indonesia experience less rainfall than usual. Average global temperatures are usually warmer than usual. La Nina: Trade winds crossing the Pacific are stronger than normal. Results in more upwelling of cold water in the east. This means more nutrients are available for fish. This pushes rainfall further out to sea. Peru and the southern US typically get less rainfall than usual. Australia and Indonesia experience more rainfall than usual. Average global temperatures are usually cooler than usual.

El Nino-Southern Oscillation (ENSO)

Trade winds weaken & warm surface water moves toward South America. Diminished fisheries off South America, drought in western Pacific, increased precipitation in southwestern North America, fewer Atlantic hurricanes* change in climate patterns in the Pacific region every 3 to 8 years Ocean surface waters are warmer than usual in Dec/Jan due to changes in wind Pressure rises in Western Pacific (Indian Ocean, Indonesia, Australia), lowers in Central & Eastern Pacific Trade winds in South Pacific weaken Upwellings in Eastern Pacific are disrupted, as warm water is not pulled west; instead, warm water from the Western Pacific is pulled east Results: Wet summers in N.W. South American Droughts in Australia (brush fires) and S.E. Asia.