4.3 El Niño-Southern Oscillation (ENSO) and other climate oscillations
4 min read•july 22, 2024
The (ENSO) is a climate pattern that shakes up the Pacific Ocean every few years. It's like a seesaw between warm and cool phases, causing changes in ocean temperatures, winds, and rainfall patterns.
ENSO's effects ripple across the globe, impacting weather, ecosystems, and human activities. From shifting fish populations to influencing crop yields, this climate dance has far-reaching consequences. Understanding ENSO helps us predict and prepare for its worldwide impacts.
El Niño-Southern Oscillation (ENSO)
Definition of ENSO phases
Top images from around the web for Definition of ENSO phases
El Niño–Southern Oscillation - Wikipedia View original
Is this image relevant?
How El Niño and La Niña climate patterns take shape View original
Is this image relevant?
El Niño–Southern Oscillation - Wikipedia View original
Is this image relevant?
El Niño–Southern Oscillation - Wikipedia View original
Is this image relevant?
How El Niño and La Niña climate patterns take shape View original
Is this image relevant?
1 of 3
Top images from around the web for Definition of ENSO phases
El Niño–Southern Oscillation - Wikipedia View original
Is this image relevant?
How El Niño and La Niña climate patterns take shape View original
Is this image relevant?
El Niño–Southern Oscillation - Wikipedia View original
Is this image relevant?
El Niño–Southern Oscillation - Wikipedia View original
Is this image relevant?
How El Niño and La Niña climate patterns take shape View original
Is this image relevant?
1 of 3
- ENSO is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean
- Involves close interaction between the ocean and atmosphere
- Occurs on average every two to seven years
- El Niño phase
- Warming of the ocean surface temperatures in the central and eastern tropical Pacific Ocean relative to average conditions (eastern coast of South America)
- Reduced upwelling of cold water along the coast of South America (Peru and Ecuador)
- Weakening or reversal of the blowing from east to west across the tropical Pacific
- La Niña phase
- Cooling of the ocean surface temperatures in the central and eastern tropical Pacific Ocean relative to average conditions
- Enhanced upwelling of cold water along the coast of South America (Peru and Ecuador)
- Strengthening of the trade winds blowing from east to west across the tropical Pacific
Processes behind ENSO development
- Normal conditions in the tropical Pacific
- Trade winds blow from east to west, pushing warm surface water towards the western Pacific (Indonesia and Australia)
- Cold, nutrient-rich water upwells along the western coast of South America (Peru and Ecuador)
- Warm air rises over the western Pacific, leading to convection and rainfall
- Development of El Niño conditions
- Weakening or reversal of the trade winds reduces the easterly wind stress on the ocean surface
- Reduced upwelling of cold water in the eastern Pacific allows the surface to warm
- Warm surface water moves towards the central and eastern Pacific, further weakening the trade winds
- Positive feedback loop between the ocean and atmosphere strengthens El Niño conditions (Bjerknes feedback)
- Development of La Niña conditions
- Strengthening of the trade winds increases the easterly wind stress on the ocean surface
- Enhanced upwelling of cold water in the eastern Pacific cools the surface
- Warm surface water is pushed further towards the western Pacific, reinforcing the trade winds
- Positive feedback loop between the ocean and atmosphere strengthens La Niña conditions
Global impacts of ENSO
- Weather patterns
- El Niño
- Increased rainfall in the eastern Pacific and along the west coast of South America (Peru and Ecuador)
- Decreased rainfall in the western Pacific (Indonesia and Australia) and parts of the Amazon rainforest
- Warmer temperatures in the eastern Pacific and western Americas
- La Niña
- Increased rainfall in the western Pacific (Indonesia and Australia) and parts of the Amazon rainforest
- Decreased rainfall in the eastern Pacific and along the west coast of South America (Peru and Ecuador)
- Cooler temperatures in the eastern Pacific and western Americas
- El Niño
- Ecosystems
- Changes in ocean productivity due to variations in upwelling and nutrient availability
- El Niño reduces upwelling and nutrient supply, decreasing marine productivity (plankton and fish populations)
- La Niña enhances upwelling and nutrient supply, increasing marine productivity
- Shifts in the distribution and abundance of marine species (tuna, sardines, and anchovies)
- Impacts on terrestrial ecosystems due to changes in precipitation patterns (droughts and floods)
- Changes in ocean productivity due to variations in upwelling and nutrient availability
- Human activities and society
- Agriculture
- Crop yields affected by changes in rainfall and temperature (rice, wheat, and maize)
- Droughts during El Niño can reduce agricultural productivity in Australia and parts of Asia
- during El Niño can damage crops in South America
- Fisheries
- Fish populations and catch rates influenced by changes in ocean productivity
- Peruvian anchoveta fishery heavily impacted by El Niño and La Niña events
- Natural disasters and infrastructure
- Increased risk of flooding and landslides during El Niño in the eastern Pacific (Peru and Ecuador)
- Increased risk of droughts and wildfires during El Niño in Australia and Southeast Asia
- Damage to infrastructure and displacement of populations due to ENSO-related extreme events
- Agriculture
Other major climate oscillations
- (NAO)
- Atmospheric pressure oscillation over the North Atlantic Ocean
- Measured by the difference in atmospheric pressure between Iceland and the Azores
- Influences weather patterns in Europe, North Africa, and eastern North America
- Positive NAO phase
- Stronger-than-average pressure difference between the Icelandic Low and the Azores High
- Increased westerly winds across the North Atlantic
- Mild and wet winters in Europe, cold and dry winters in northern Canada and Greenland
- Negative NAO phase
- Weaker-than-average pressure difference between the Icelandic Low and the Azores High
- Reduced westerly winds across the North Atlantic
- Cold and dry winters in Europe, mild and wet winters in northern Canada and Greenland
- Atmospheric pressure oscillation over the North Atlantic Ocean
- (PDO)
- Long-term ocean temperature variability in the North Pacific Ocean
- Shifts between warm and cool phases on a multi-decadal timescale (20-30 years)
- Warm PDO phase
- Warmer-than-average sea surface temperatures along the west coast of North America (Alaska and California)
- Cooler-than-average temperatures in the central North Pacific
- Decreased upwelling and marine productivity along the west coast of North America
- Cool PDO phase
- Cooler-than-average sea surface temperatures along the west coast of North America
- Warmer-than-average temperatures in the central North Pacific
- Increased upwelling and marine productivity along the west coast of North America
- Influences climate and ecosystem dynamics in the North Pacific and surrounding regions
- Affects salmon populations and fisheries along the west coast of North America
- Modulates the impact of ENSO on North American climate (constructive or destructive interference)
- Long-term ocean temperature variability in the North Pacific Ocean
Key Terms to Review (19)
Buoys: Buoys are floating devices used in oceans and large bodies of water for navigation, data collection, and environmental monitoring. In the context of climate science, buoys play a crucial role in tracking ocean conditions, which are vital for understanding phenomena like the El Niño-Southern Oscillation (ENSO) and other climate oscillations. By providing real-time data on temperature, salinity, and currents, buoys help scientists predict climate patterns and assess their impacts on global weather systems.
Climate extremes: Climate extremes refer to significant deviations from average weather conditions, resulting in unusual and severe weather events, such as extreme heat waves, heavy rainfall, droughts, and powerful storms. These events are closely linked to natural climate oscillations like the El Niño-Southern Oscillation (ENSO), which can amplify or diminish the frequency and intensity of such extremes. Understanding these phenomena helps in predicting their impacts on ecosystems, agriculture, and human societies.
David Battisti: David Battisti is a prominent climate scientist known for his research on climate variability, particularly in relation to the El Niño-Southern Oscillation (ENSO) and its impacts on global weather patterns. His work has significantly advanced the understanding of how ENSO influences climate fluctuations and extreme weather events, linking oceanic and atmospheric processes.
Drought: Drought is a prolonged period of abnormally low rainfall, leading to a water shortage that can have severe impacts on agriculture, ecosystems, and human communities. It affects food production, water supply, and the overall health of the environment, making it a critical concern in understanding climate patterns and resource management.
Dynamical models: Dynamical models are mathematical representations used to simulate and understand the behavior of complex systems over time, particularly in relation to climate phenomena. These models utilize equations that describe how variables change in response to one another and external influences, making them essential for predicting future climate states. They are especially crucial for analyzing climate oscillations like the El Niño-Southern Oscillation (ENSO), helping researchers understand both short-term fluctuations and long-term trends in climate patterns.
El Niño: El Niño is a climate pattern characterized by the periodic warming of sea surface temperatures in the central and eastern Pacific Ocean, significantly influencing global weather and climate. This phenomenon can disrupt normal weather patterns, leading to changes in precipitation, temperature, and storm activity around the world.
El Niño-Southern Oscillation: The El Niño-Southern Oscillation (ENSO) is a climate pattern that describes the fluctuating ocean-atmosphere interactions in the central and eastern tropical Pacific Ocean. This phenomenon includes two phases: El Niño, characterized by warmer ocean temperatures, and La Niña, marked by cooler ocean temperatures. ENSO plays a significant role in influencing global weather patterns, including changes in precipitation and temperature, which can lead to extreme weather events and shifts in climate behavior.
Flooding: Flooding is the overflow of water onto land that is normally dry, often caused by heavy rainfall, melting snow, or river overflow. This phenomenon significantly impacts water resources and availability, as well as the natural processes involved in the hydrologic cycle. Understanding flooding is essential to grasp how climate patterns, such as El Niño and other climate oscillations, influence weather conditions that lead to increased precipitation and potential flood events.
General Circulation Models: General circulation models (GCMs) are complex computer simulations that represent the Earth's atmosphere and oceans to understand and predict climate patterns and changes. These models use mathematical equations to simulate physical processes, including heat exchange, wind patterns, and moisture distribution. GCMs are essential tools for examining how different factors influence climate, particularly through atmosphere-ocean interactions and climate oscillations like the El Niño-Southern Oscillation.
Interannual variability: Interannual variability refers to the fluctuations in climate or weather patterns that occur from year to year, affecting temperature, precipitation, and other climatic conditions. This concept is crucial for understanding how climate systems respond to various influences, such as oceanic and atmospheric interactions, particularly during events like El Niño and La Niña, which can significantly alter global weather patterns over different years.
Jacob Bjerknes: Jacob Bjerknes was a Norwegian meteorologist who made significant contributions to our understanding of the El Niño-Southern Oscillation (ENSO) phenomenon and its impact on global climate patterns. His work in the mid-20th century laid the groundwork for modern climate science, particularly in how oceanic and atmospheric interactions can lead to climate oscillations, including variations in temperature and precipitation across the globe.
La Niña: La Niña is a climate pattern characterized by cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean, which influences weather patterns across the globe. This phenomenon can lead to significant changes in temperature and precipitation, impacting global climate trends and variability, as well as extreme weather events.
North Atlantic Oscillation: The North Atlantic Oscillation (NAO) is a climate phenomenon characterized by fluctuations in the difference of atmospheric pressure at sea level between the Icelandic low and the Azores high. These fluctuations influence weather patterns in the North Atlantic region, impacting precipitation, temperature, and storm tracks in Europe and North America. The NAO is an essential aspect of internal climate variability and interacts with other oscillations, affecting global weather systems.
Ocean-atmosphere interaction: Ocean-atmosphere interaction refers to the complex and dynamic relationship between the ocean and the atmosphere, which significantly influences climate patterns and weather systems. This interaction is driven by processes such as heat exchange, moisture transfer, and the movement of ocean currents, which can affect atmospheric circulation and global climate variability. Understanding this relationship is crucial for grasping phenomena like El Niño and other climate oscillations that can lead to dramatic changes in weather patterns worldwide.
Pacific Decadal Oscillation: The Pacific Decadal Oscillation (PDO) is a long-term oceanic and atmospheric phenomenon characterized by fluctuations in sea surface temperatures and associated climate patterns in the North Pacific Ocean. The PDO has a significant impact on climate variability over periods of 20 to 30 years, influencing weather patterns, marine ecosystems, and global climate interactions, particularly in relation to other climate oscillations like the El Niño-Southern Oscillation.
Satellite observations: Satellite observations refer to the collection of data from space using satellites equipped with various sensors to monitor Earth's atmosphere, land, and oceans. This technology plays a crucial role in understanding climate phenomena like the El Niño-Southern Oscillation (ENSO), as it allows scientists to gather real-time information on sea surface temperatures, wind patterns, and other critical indicators that influence global climate systems.
Sea Surface Temperature: Sea surface temperature (SST) refers to the temperature of the upper layer of the ocean, which plays a crucial role in regulating climate and weather patterns. Variations in SST can affect atmospheric circulation, influence storm formation, and contribute to climate phenomena such as El Niño and La Niña. Understanding SST is essential for grasping how the ocean interacts with the atmosphere and impacts global climate systems.
Teleconnections: Teleconnections refer to the climate phenomenon where weather patterns or climate anomalies in one region can influence weather and climate in distant regions. This concept is crucial for understanding how interconnected our global climate system is, particularly in the context of events like El Niño-Southern Oscillation (ENSO), which can create significant impacts on weather patterns far from their origin.
Trade winds: Trade winds are persistent easterly winds that flow in the tropics, predominantly between the equator and approximately 30 degrees latitude in both hemispheres. These winds play a crucial role in global atmospheric circulation, driving ocean currents and influencing weather patterns across the planet. They are vital for understanding both the general circulation of the atmosphere and phenomena like El Niño.