El Niño-La Niña Weather Patterns

Why in news?

A new study projects that climate change will significantly impact El Niño-La Niña weather patterns approximately by 2030.

What are the findings of the study?

• Study published in Nature journal – It has projected that climate change will impact El Niño-La Niña weather patterns approximately by 2030, a decade before what was earlier predicted.
• If Central Pacific and Equatorial Pacific are not separated, sea surface temperature (SST) variability from ENSO will occur almost four decades earlier than previously suggested.
• WMO prediction – In 2022, the World Meteorological Organisation (WMO) predicted the first “Triple dip” La Niña of the century.
• This is only the third time since 1950 that a triple dip La Nina has been observed.

At present, India is witnessing an extended triple dip La Niña.

What is El Niño?

• El Niño is a loose translation of “little boy” or “Christ child” in Spanish.
• Earlier, it was also called “El Niño de Navidad” since it peaks around December.
• El Niño is the warming of sea waters in Central-east Equatorial Pacific that occurs every few years (Warm phase off the coast of Peru).
• During El Niño, surface temperatures in the equatorial Pacific rise
• This weakens the trade winds — east-west winds that blow near the Equator.
• Due to El Niño, easterly trade winds that blow from the Americas towards Asia change direction to turn into westerlies.
• It thus brings warm water from the western Pacific towards America.

Effects of El Niño Phenomenon

• Weather - El Niño causes dry, warm winter in Northern U.S. and Canada and increased flooding risk on the U.S. gulf coast and southeastern U.S.
• It brings drought to Indonesia and Australia.
• In India, an El Nino event is strongly linked to suppressed rainfall in the monsoon season.
• Marine resource - Under El Niño, upwelling (deeper waters rise towards the surface) of deeper waters is reduced, thus reducing phytoplankton off the coast.
• Fish that eat phytoplankton are affected, followed by other organisms higher up the food chain.
• Warm water - Warmer water carries tropical species towards colder areas, disrupting multiple ecosystems.
• Airflow above the ocean - Heat redistribution on the surface impacts airflows above the ocean.

What is La Niña?

• La Niña or “Little girl” is the opposite of El Niño.
• La Niña sees cooler than average sea surface temperatures in the equatorial Pacific region.
• It is the “Cool phase”.
• Trade winds are stronger than usual, pushing warmer water towards Asia.

Effects of La Niña Phenomenon

• Weather - Pacific cold waters close to the Americas push jet streams (narrow bands of strong winds in the upper atmosphere) northwards.
• La Niña leads to drier conditions in Southern U.S.
• La Niña has been associated with heavy floods in Australia.
• In the Indian context, La Niña is associated with good rainfall during the monsoon season.
• Ocean water - On the American west coast, upwelling increases, bringing nutrient-rich water to the surface.

What about El Niño Southern Oscillation (ENSO)?

• The combination of El Niño, La Niña, and the neutral state between the two opposite effects is called the El Niño Southern Oscillation (ENSO).
• The phenomenon was discovered by Sir Gilbert Walker.

References

1. The Hindu│ El Niño, La Niña and changing weather patterns
2. The Indian Express│ The ‘triple dip’ La Niña
3. National Ocean Service│ What are El Niño and La Niña?