Remember “normal” ocean circulation?

El Nino? (warm)

• Trade winds weaken• Thermocline drops• Upwelling is cut off• SST rises in E.Pacific• High & Low pressure areas

in Pacific reverse• Disrupts fish/bird

populations in E.Pacific• Occur every 2-7 years• Lasts 12-18 months

La Nina? (cold)

• Trade winds strengthen

• SST decrease in E.Pacific

• Upwelling increases• Occurs every 3-5 years• Lasts 9-12 months

• Prentice Hall Textbook animation link

• Prentice Hall Textbook animation link

• Prentice Hall Textbook animation link

• Normal

• El nino – strong counter-current

Sea surface anomalies associated with El Nino

SST differences between El Nino and La Nina

A

B

C

QUIZ! Which is which…Normal, El Nino, La Nina?

Were you’re predictions correct?

What are the effects of El Nino?

Brush fires caused by drought

Increased Tropical Storms

Devastating floods

Peruvian anchovy populations decline

Winter NH

• El Nino

• La Nina

Summer NH

• El Nino

• La Nina

El nino - precipitation

El nino - precipitation

Hurricanes• El Niño contributes to more eastern Pacific hurricanes and fewer

Atlantic hurricanes.

• La Niña contributes to fewer eastern Pacific hurricanes and more Atlantic hurricanes.

US hurricane damage

US TornadosTornado activity

Depends on the location of the polar jet stream

• El Nino: More to the south

• La Nina: more to the north

Measurements!

How can we predict an El Nino or La Nina event?

Buoys

Measure...• temperatur

e• currents• winds

Radiosonde

• Weather balloon• Monitors global

weather and climate patterns

Satellites

Provide data on:• Rainfall• Wind• Ocean temp.• Sea surface

height• Ocean color• Surface

currents

TOPEX/Poseidon (T/P)

Click here to find out what the current sea surface temperatures are.

Are we in an El Nino, La Nina, or neither?