Short term Climate change El Niño and La Niña What causes them? Why do they occur?

El Niño and La Niña Are short term changes in the Tropical Pacific Ocean by changes in ocean surface currents and prevailing winds. Both influence weather patterns all over the world.

What is El Niño? A climate event that occurs every two to seven years in the Pacific Ocean , during which winds shift and push warm water toward the coast of South America. Unusual pattern of warm winds forms over the western Pacific. Causes vast sheet of warm water to move eastward toward the South American coast. Disrupts the cold ocean currents along the western coast of South America. Changes weather pattern. Often bring severe conditions such as heavy rains normally in dry areas or droughts in wet areas.

The Effects of El Niño are Worldwide Wet winters over southeastern United States Drought in Indonesia and Australia, and other places that are typically wet Flooding in South America in areas typically dry Wildfires and mudslides Warmer winters in the upper Midwest united states and Canada

The Effects of El Niño are Worldwide El Niño’s warm current of nutrient-poor tropical water replaces the cold, nutrient-rich surface water where Peru’s fishing industry usually is vibrant

What is La Niña? Opposite of El Niño event. A climate event in the eastern Pacific Ocean in which surface waters are colder than normal. Brings colder than normal winters and greater precipitation to the Pacific Northwest and the north central United States. Greater hurricane activity in the western Atlantic

Under normal conditions, easterly trade winds move water and air warmed by the sun towards the west http://sphere.ssec.wisc.edu/20130315/ This also creates an upwelling of nutrient-rich cold water along the coasts of Peru and Ecuador What is Upwelling? – The movement of cold water upward from the deep ocean that is caused by wind.

Under El Niño conditions, warm, nutrient-poor water slumps towards the east because of weakening winds. The nutrient-rich cold water does not get pulled up as much – Little upwelling

Under La Niña conditions, unusually cold water pushes up in the east Pacific Often follows El Niño Too much upwelling

http://www. youtube. com/watch http://www.youtube.com/watch?list=PLKJqO6lS_5VbdUK9aT9IfsPPfX4D-HHZC&v=tyPq86yM_Ic#t=25

El Niño vs. La Niña El Niño La Niña Usually more intense effects than La Niña Unusually warm ocean temperatures in eastern Pacific (west united states) Summers in central united states tend to be wetter and cooler Usually follows El Niño, but not always Unusually cold ocean temperatures in eastern Pacific (west united states) Summers in central united states tend to be drier and warmer

El Niño vs. La Niña El Niño La Niña Causes drier weather on West Pacific (Australia, Indonesia, etc) Warmer winters in the upper Midwest states and Canada Wet winters over southeastern United States Causes wetter weather on West Pacific (Australia, Indonesia, etc) Colder winters in the upper Midwest states and Canada Dry winters over southeastern United States

La Niña to blame? Recent droughts occurred during latest La Niña