El Niño-Southern Oscillation

Definition

El Niño-Southern Oscillation (ENSO) is a climate phenomenon characterized by variations in ocean temperatures and atmospheric conditions in the central and eastern Pacific Ocean. This oscillation consists of two main phases: El Niño, which brings warmer ocean temperatures, and La Niña, which brings cooler temperatures, both significantly impacting global weather patterns, marine ecosystems, and biogeochemical cycles in the open ocean.

5 Must Know Facts For Your Next Test

1. El Niño events typically occur every 2 to 7 years and can last from several months to a couple of years, altering ocean currents and temperature profiles.
2. During an El Niño phase, the warm water pools in the eastern Pacific, disrupting normal upwelling processes that are vital for marine life and impacting fish populations.
3. La Niña, the counterpart to El Niño, is characterized by colder than average ocean temperatures in the central Pacific and can lead to opposite weather effects, such as increased hurricane activity in the Atlantic.
4. ENSO influences global weather patterns, including increased rainfall in some regions and droughts in others, affecting agricultural productivity and water resources.
5. The variability in nutrient availability during ENSO phases directly impacts marine biogeochemistry, influencing carbon cycling and primary production in oceanic ecosystems.

Review Questions

• How does the El Niño-Southern Oscillation influence marine ecosystems and their biogeochemistry?
  • ENSO has a significant impact on marine ecosystems through its effects on ocean temperatures and currents. During El Niño events, warmer waters reduce upwelling, leading to lower nutrient availability. This decline in nutrients can result in reduced primary productivity and affect food webs in open ocean environments. Conversely, during La Niña events, enhanced upwelling promotes nutrient availability, supporting a more productive marine ecosystem.
• Discuss the implications of El Niño-Southern Oscillation for global weather patterns and how these changes affect biogeochemical cycles.
  • El Niño-Southern Oscillation has far-reaching implications for global weather patterns, causing changes such as increased rainfall or droughts across different regions. These shifts can disrupt local agricultural systems and water availability. Furthermore, changes in precipitation patterns impact biogeochemical cycles by altering runoff dynamics and nutrient inputs into coastal marine systems, affecting overall ocean health and productivity.
• Evaluate the long-term impacts of repeated El Niño-Southern Oscillation events on oceanic carbon cycling and ecosystem resilience.
  • Repeated ENSO events can lead to significant long-term changes in oceanic carbon cycling by affecting primary productivity rates and altering species compositions within marine ecosystems. As warmer waters affect the distribution of phytoplankton, key players in carbon fixation, this can lead to shifts in carbon storage capabilities of the oceans. Over time, these impacts may reduce ecosystem resilience, making them more vulnerable to other stressors such as climate change and pollution, further complicating biogeochemical interactions within the ocean.

Related terms

Thermocline: The layer in a body of water where the temperature changes rapidly with depth, affecting nutrient availability and marine life.

Upwelling:

The process by which deep, nutrient-rich waters rise to the surface, often enhanced by ENSO events, supporting biological productivity.

Biogeochemical Cycle: The pathways by which chemical elements and compounds move through biotic (living) and abiotic (non-living) components of the Earth, often influenced by climatic factors like ENSO.