Chapter 7 Ocean Circulation:

El Niño

Essentials of Oceanography

7th Edition

Thurman/Trujillo

El Niño-Southern Oscillation (ENSO)

El Niño (Spanish for “the Child” in reference to baby Jesus) = warm surface current in equatorial eastern Pacific that occurs periodically around ChristmastimeSouthern Oscillation = change in atmospheric pressure over Pacific Ocean accompanying El NiñoENSO describes a combined oceanic-atmospheric disturbance

Questions about El Niño

What does an El Niño have to do with the price of eggs?

What is La Niña?

What kind of weather does El Niño bring to southern California?

Is this an El Niño year?

Normal conditions in the Pacific Ocean (pg. 218)

Figure 7-18a

El Niño conditions (ENSO warm phase) (pg. 218)

Figure 7-18b

La Niña conditions (ENSO cool phase; opposite of El Niño)

Figure 7-18c

Anomaly maps

Anomaly (a = without, nomos = law) maps show the difference from normal conditionsSea Surface Temperature (SST) anomaly maps are useful for identifying unusually warm or cool water:Positive SST anomaly values = water warmer than normalNegative SST anomaly values = water cooler than normal

January 1998 SST anomaly map

Figure 7-19aPg. 220

January 2000 SST anomaly map

Figure 7-19bPg. 220

Offshore California

SST anomaly map:

January 1998

Offshore California

SST anomaly map:

January 1999

(1 year later)

El Niño/La Niña & weather in southern California

Typical weather during El Niño?Strong El Niños: Lots of powerful storms (good waves), lots of rain (1997-1998 = more than double our normal rainfall), but not always…Moderate/Weak El Niños: can have drought conditions or lots of rain or no effect at all

Typical weather during La Niña?Extremely dry conditions (2000-2001 = 1/3 normal rainfall)

El Niño recurrence interval

Typical recurrence interval for El Niños = 2-12 yearsPacific has alternated between El Niño and La Niña events since 1950

Figure 7-20

Pg. 221

Effects of severe El Niños

Figure 7-21

Pg. 222

El Niño visualizations

Internet site for El Niño animation

Latest SST anomaly map of the tropical Pacific

Forecast SST anomalies: Can we expect another El Niño year?

9-month forecast of tropical Pacific SST anomalies

Alternate link for 9-month forecast of tropical Pacific SST anomalies (from Palomar Oceanography Home Page)

End of El Niño presentation

Essentials of Oceanography

7th Edition

Thurman/Trujillo