Geo P2 Option B Lesson 4
La Nina Conditions
- An intensification of the normal conditions - The trade winds are much stronger pushing even more warm surface water closer to Australia and Indonesia - This causes heavier than normal rainfall often resulting in floods and landslides - Along the South American coast there is a cold water upwelling, fish catching improves and drier than normal conditions occur over Peru
La Nina Effects
- Causes cold upwelling along the Peruvian coast - good for fishing and local economies - Heavier than normal rainfall can lead to flooding and landslides in Australia and Indonesia - Drought can occur along the coast of Peru and Chile - Higher ocean temps in Indonesia can cause coral bleaching and lose tourism - More cyclones in the western pacific - affects the Philippines - No droughts in Africa and India is good for crops and food production - Cold conditions and heavy snowfall along the coast of BC
El Nino Southern Oscillation (ENSO)
- Describe the position of warm and cool water, and the strength of winds and atmospheric conditions in the equatorial pacific ocean region - These conditions aren't always the same as there is a regular oscillation - It can go from one extreme La Nina to the other El Nino - Each event can last up to 2 years
El Nino Effects
- Low fish catches on the coast of Peru, due to the absence of nutrient-rich cold water upwelling has negative affects on communities that rely on fishing - Heaving rain (flooding) along the West coast of South America (Peru, Ecuador) creates landslides that can kill - Rain triggers the blooming of wildflowers in the Atacama desert which is good for tourism - Drought in Australia, Southern Africa, and Indonesia - In Africa, can kill crops and cattle leading to starvation - In Australia dry conditions lead to many bushfires that can destroy communities and forest fires and Indonesia - Smoke can cause health problems and even disrupt air traffic - Causes increase in storms, coastal erosion and landslides along Californian coast - On the coast of BC it causes higher temperatures and less snow - bad for tourism
El Nino Conditions
- Occurs when trade winds weaken or even reverse to blow east instead of west - Causes the warm water collected in the west to flow back to the eastern side of the pacific - From this the clouds and rainfall also come back east - So rainfall that would normally occur over Indonesia and Australia falls over the deserts of Peru causing flooding - This also makes Australia and Indonesia very dry resulting in droughts and fires - Because of the weak trade winds the warm water now accumulates on the coast of South America and cold water upwelling goes away and so do the fish - This leads to a bad fishing season for Peruvians
Normal Conditions (The Walker Circulation)
- Trade winds or easterlies blow from South America to the area in between Australia and Indonesia - This pushes warm equatorial surface water to Australia and Indonesia - The increase in warm water increases temperatures and precipitation in the regions
