El Niño and La Niña

ENSO describes a combined oceanic-atmospheric disturbance El Niño (Spanish for “the Child” in reference to baby Jesus) warm surface current in equatorial eastern Pacific that occurs periodically around Christmastime. The average period length is 5 years. occurs for only seven to nine months. fluctuates between warmer-than-average Southern Oscillation = change in atmospheric pressure over Pacific Ocean accompanying El Niño Sir Gilbert Walker and colleagues extended the early studies and determined. ENSO describes a combined oceanic-atmospheric disturbance

La Niña: It is a coupled ocean-atmosphere phenomenon that is the counterpart of El Niño or "anti-El Niño“ During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3–5 °C. In the United States, an episode of La Niña is defined as a period of at least 5 months of La Niña conditions. The name La Niña originates from Spanish, meaning "the girl", colder-than-average conditions

Normal conditions in the Pacific Ocean

El Niño conditions (ENSO warm phase)

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

Typical January to March Weather Anomalies El Nino La Nina

Sea Surface Temperatures Equatorial cold tongue is weaker than average or absent during El Niño, resulting in positive SST anomalies

El Niño recurrence interval Typical recurrence interval for El Niños = 2-7 years Pacific has alternated between El Niño and La Niña events since 1965

Effects of severe El Niños

1. Worldwide Bleaching of Coral reef

2. Impact over Marine life

El Niño and La Niña impacts ocean productivity Normal Conditions and La Nina = more productive Nutrients                                                             El Nino Conditions = less productive During an El Niño event, the southeast trade winds weaken and so does the amount upwelling in the eastern Pacific. The deeper thermocline means that any upwelling that does occur is unable to tap into the rich nutrients found in deeper waters. Consequently, warm nutrient-poor water predominates the region and a decrease in the fish population is observed. During non-El Niño years, the southeast trade winds, drag surface water westward away from shore. As surface water moves away, upwelling brings up colder waters from depths of 40-80 meters or more. This deep sea water is rich in nutrients which can sustain large fish populations.

3. Flood

4. Drought

5. Coastal Erosion

6. Tropical cyclone

7. Forest Fire

8. Birds life

9. El Niño an Jet Stream Jet stream (~12km) shifts North Normal/La Nina El Nino Jet stream (~12km) shifts North during El Nino years (thin arrows) More storms develop in the Gulf of Mexico, bringing heavy rains to much of the southern United States during El Nino. Jetstream is at ~12km height.

Global La Niña Impacts

Typical Global La Niña Impacts Region Period Impact Indonesia Life of event Wetter Northeast Brazil March-May Central America /Mexico May-October West Coast South America Drier Central South America June-December Southeast Africa December-February