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Topic 12 El Niño. GEOL 2503 Introduction to Oceanography. El Ni o. A disruption of the ocean-atmosphere system in the tropical Pacific Has important consequences for weather around the globe Frequently occurs around Christmas. Normal conditions. Strong trrade winds-.

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Topic 12 El Niño

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Topic 12 el ni o

Topic 12El Niño

GEOL 2503

Introduction to Oceanography

El ni o

El Nio

  • A disruption of the ocean-atmosphere system in the tropical Pacific

  • Has important consequences for weather around the globe

  • Frequently occurs around Christmas

Topic 12 el ni o

Normal conditions

Strong trrade winds-

El ni o resources

El Niño resources

  • NOAA:

  • See animations at:


El ni o characteristics

El Niño Characteristics

  • Normally develops in W. tropical Pacific

  • Often results in natural disasters

  • Occurs every 2 to 10 years

  • Most recent and severe events in 1953, ‘57-’58, ‘65, ‘72-’73, ‘76-’77, ‘82-’83, ‘91-’92, ‘97-’98, ‘02-’04, ‘06-’07, ’09’10

Normal conditions

Normal Conditions

El ni o conditions

El Niño Conditions

El ni o and productivity

El Nio and Productivity

  • During normal conditions, major upwelling brings nutrients and carbon dioxide into the photic zone

  • Creates conditions of very high productivity (plants) and fish that feed on plants and other small fish

  • El Nio shuts down the upwelling and decreases productivity

El ni o sea surface temperatures

El Niño Sea Surface Temperatures

La ni a

La Niña

  • Trade winds strengthen and increase upwelling

  • Unusually cold ocean temperatures in the Equatorial Pacific

  • “Super normal” or opposite of El Niño

La ni a conditions

La Niña Conditions

Topic 12 el ni o

El Niño—large pool of warm surface water in western Pacific

La Niña—so much upwelling of cold water in eastern Pacific that it spreads to west, cooling sea surface temperatures

Topic 12 el ni o

El Niño condition: departures from normal

La ni a impacts in u s

La Niña Impacts in U.S.

  • Warmer winters in the Southeast

  • Cooler winters in the Northwest

Topic 12 el ni o

El Niño and La Niña and the Asian monsoons. When surface temperatures in the eastern equatorial Pacific are warmer than usual (an El Niño event), heavy rains hit East Africa and droughts beset India, Indonesia, and Australia. When ocean conditions flip-flop (a La Niña), so do rainfall patterns across Asia. From

Topic 12 el ni o


  • El Niño/Southern Oscillation

  • The Southern Oscillation refers to changes in sea level air pressure patterns in the Southern Pacific Ocean between Tahiti and Darwin, Australia.

Topic 12 el ni o

ENSO—note the movement of the low pressure center


El Niño

Southern oscillation so

“Southern Oscillation” (SO)

  • Trade winds weaken or fail

  • Tropical winds reverse and go east instead of west

  • Atmospheric pressure cells reverse

  • Wet areas become dry (drought)

  • Dry areas get flooded

  • “Oscillates” taking 3-5 months

Southern oscillation index

Southern Oscillation Index

Pressure differences between Tahiti and Darwin, Australia

Topic 12 el ni o

Coupled Ocean-Atmosphere Circulation

Non El Niño

El Niño

Ocean s response to the so

Ocean’s Response to the SO

  • Warm water moves to the east

  • Elevates sea surface temperatures (SSTs) in SE Pacific

  • Shuts down upwelling, can induce downwelling

  • Reduces available nutrients

  • Kills fish and sea birds - especially bad off Peru

El ni o and hurricanes

El Niño and Hurricanes

  • Biggest influence is in North

  • In years with moderate to strong El Niño, the North Atlantic basin experiences:

    • A substantial reduction in number of hurricanes

    • A 60% reduction in numbers of hurricane days

    • An overall reduction in system intensity

Tao triton


  • Tropical Atmosphere Ocean Project (TAO)

  • Triangle Trans-Ocean Buoy Network (TRITON)

  • Real-time data from moored ocean buoys for improved detection, understanding and prediction of El Niño and La Niña.

Topic 12 el ni o

Moored Buoys



Sea surface temperature winds 20 c isotherm and upper ocean temperature and current at the equator

Sea Surface Temperature, Winds, 20°C Isotherm, and Upper Ocean Temperature and Current at the Equator

To view this animation and others, visit the TAO/TRITON data display page at www.pmel.noaa.gove/tao/jsdisplay/ani/html.

Topic 12 el ni o


  • Conductivity, Temperature, Depth

  • Detect how the conductivity and temperature of the water column changes relative to depth.

  • Salinity can be derived from these two variables.

  • Water sampling is often done at specific depths so scientists can learn the physical properties of the water column are at that particular place and time.

Topic 12 el ni o

Deploying a CTD array

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