APES Video Notes 4.9 - El Nino & La Nina

Summary

In this lesson, Mr. Speeds explores the El Niño Southern Oscillation (ENSO), explaining how changes in ocean temperatures, wind patterns, and atmospheric pressure affect global weather. The video delves into the mechanisms of ocean circulation, including gyres and upwelling, and their influence on regions like the Americas and Southeast Asia. It highlights the environmental impacts of El Niño and La Niña events, from droughts and flooding to disruptions in fisheries and agriculture. Viewers are encouraged to analyze how these phenomena pose environmental challenges and affect local economies.

Takeaways

• 😀 The El Nino Southern Oscillation (ENSO) is a periodic shift in atmospheric pressure, wind patterns, and ocean temperatures in the Southern Pacific, influencing global weather and ocean currents.
• 🌊 Ocean gyres are large circulation patterns caused by global wind patterns, with clockwise rotation in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
• 🔄 Upwelling zones bring cold, nutrient-rich water to the surface, supporting productive fisheries along coastlines like South America and North America.
• 🌍 The thermohaline circulation is a key process that connects oceans globally, mixing salt, nutrients, and temperature, influencing the climate of different regions.
• 💨 During normal conditions, eastern trade winds push warm surface water from east to west, leading to higher rainfall in Southeast Asia and Australia and upwelling along the Americas.
• 🌧️ El Nino events weaken trade winds, causing warm water to shift towards the Americas, which leads to milder winters in North America but causes drought and less rainfall in Southeast Asia and Australia.
• 🌪️ El Nino's impact includes suppressed upwelling off the coast of South America, harming fisheries and affecting the food chain due to reduced nutrients in the water.
• ☀️ El Nino causes warmer and wetter conditions in the Americas, resulting in floods, agricultural damage, and economic loss, especially for farming and fishing industries.
• ❄️ La Nina events are characterized by stronger-than-normal trade winds, causing cooler, drier conditions in the Americas and more rain in Southeast Asia and Australia.
• 🌾 La Nina can lead to more intense monsoon activity in Southeast Asia, increasing the risk of flooding, while boosting upwelling off the coast of South America, benefiting fisheries and reducing agricultural impacts.

Q & A

What is the El Niño Southern Oscillation (ENSO)?

The El Niño Southern Oscillation (ENSO) is a periodic shift in atmospheric pressure, wind patterns, and ocean temperatures in the Southern Pacific. It consists of El Niño and La Niña events, which represent the extremes of this oscillation, and they significantly impact global weather and environmental conditions.

What are the main global ocean circulation patterns discussed in the script?

The script discusses gyres, which are large ocean circulation patterns influenced by global wind patterns. In the Northern Hemisphere, these currents move clockwise, while in the Southern Hemisphere, they move counterclockwise. The script also covers the concept of upwelling, where surface water moves away from landmasses, allowing colder, nutrient-rich water to rise.

How do gyres influence ocean currents?

Gyres are driven by prevailing wind patterns. In the equatorial region, the trade winds move water from east to west, which causes warm surface water to shift towards Southeast Asia and Australia. At higher latitudes, westerly winds shift water from west to east. These winds create predictable clockwise or counterclockwise currents, depending on the hemisphere.

What is upwelling, and why is it important?

Upwelling is the process where warm surface waters move away from a landmass, allowing colder, deeper waters to rise and replace them. This process brings oxygen, nutrients, and sediments to the surface, supporting highly productive ecosystems and fisheries, especially along the coasts of South and North America.

What role does thermohaline circulation play in ocean mixing?

Thermohaline circulation involves the movement of ocean currents that connect all the world's oceans, mixing salt, nutrients, and temperature. This circulation helps distribute heat, regulate climate, and mix ocean waters globally. As warm water from the Gulf of Mexico moves north, it cools and becomes denser, sinking and contributing to the global circulation.

How does thermohaline circulation affect Europe's climate?

Thermohaline circulation brings warm water from the Gulf Stream to Europe, moderating its climate. The warm water helps keep temperatures higher than in other regions at the same latitude, such as Canada, making Europe's climate milder and more temperate.

What happens during normal (neutral) conditions in the Pacific Ocean?

Under normal conditions, trade winds blow from east to west across the equator, pushing warm surface water towards Southeast Asia and Australia. This causes cooler water to rise through upwelling along the coast of South America. This setup leads to productive fisheries along the Pacific coast of South America and higher rainfall in Southeast Asia and Australia.

How do El Niño events impact global weather?

During an El Niño event, the trade winds weaken or reverse direction, pushing warm water towards the Americas. This leads to milder winters in North America, but also causes warmer and wetter conditions in the Americas, potentially resulting in flooding. The suppression of upwelling leads to reduced fish populations along the South American coast, harming local fisheries.

What are the environmental consequences of a La Niña event?

A La Niña event strengthens the trade winds, pushing warm surface waters back towards Southeast Asia and Australia, which causes cooler and drier conditions in the Americas. This can lead to droughts and less precipitation in the western Pacific, but also intensifies upwelling off the coast of South America, making fisheries there more productive.

How does El Niño affect agricultural and fishing activities in South America?

El Niño brings warmer ocean temperatures to the west coast of South America, suppressing upwelling, which reduces nutrient availability and disrupts local fisheries. Additionally, the increased rainfall caused by El Niño often leads to flooding, damaging crops and causing losses for farmers who rely on consistent weather patterns.