El Niño-Southern Oscillation

Definition

El Niño-Southern Oscillation (ENSO) is a climate pattern characterized by periodic fluctuations in sea surface temperatures and atmospheric pressure in the central and eastern tropical Pacific Ocean. This oscillation influences global weather patterns, including precipitation and temperature variations, significantly affecting the general circulation of the atmosphere.

5 Must Know Facts For Your Next Test

1. ENSO has three phases: El Niño (warm phase), La Niña (cool phase), and Neutral, each influencing global climate differently.
2. During El Niño events, trade winds weaken, leading to warmer ocean temperatures which can cause heavy rainfall in some regions and droughts in others.
3. The Southern Oscillation refers to the shift in atmospheric pressure between the eastern and western Pacific, closely linked to sea surface temperature changes.
4. ENSO events typically occur every 2 to 7 years and can last anywhere from 9 to 12 months, but their effects can linger for years.
5. El Niño can significantly impact agriculture, fisheries, and water resources worldwide due to its influence on weather patterns.

Review Questions

• How does the El Niño-Southern Oscillation affect global weather patterns?
  • The El Niño-Southern Oscillation alters trade winds and sea surface temperatures in the Pacific Ocean, leading to widespread changes in global weather. During an El Niño event, warmer ocean temperatures cause increased rainfall in coastal regions of South America and can lead to droughts in places like Indonesia and Australia. This shift impacts not only local weather but also larger atmospheric circulation patterns that can affect temperatures and precipitation far beyond the Pacific region.
• Discuss the relationship between ENSO phases and the Walker Circulation.
  • ENSO phases directly influence Walker Circulation, which is a critical component of tropical atmospheric dynamics. During El Niño, weakened trade winds reduce the east-west pressure gradient that drives this circulation, disrupting normal weather patterns. Conversely, La Niña strengthens the Walker Circulation, resulting in enhanced trade winds and altered precipitation patterns, demonstrating how ENSO phases have profound effects on global atmospheric circulation.
• Evaluate the socio-economic impacts of an El Niño event on global communities.
  • An El Niño event can have significant socio-economic repercussions worldwide due to its influence on climate variability. For instance, countries reliant on agriculture may face crop failures due to unexpected droughts or floods, leading to food shortages and economic distress. Additionally, fisheries might suffer from changes in ocean temperatures affecting fish populations, impacting local economies dependent on fishing. Overall, the cascading effects of an El Niño event can strain resources and disrupt livelihoods across different sectors.

Related terms

La Niña:

La Niña is the counterpart to El Niño, marked by cooler than average sea surface temperatures in the central and eastern Pacific Ocean, leading to opposite climatic effects.

Walker Circulation:

Walker Circulation is an atmospheric circulation pattern in the tropics that is altered during ENSO events, impacting trade winds and weather systems across the globe.

Pacific Decadal Oscillation: The Pacific Decadal Oscillation is a long-term oceanic and atmospheric phenomenon in the North Pacific Ocean that can interact with ENSO, affecting climate variability over decades.