4.9 - El Niño and La Niña

Question 1

What are gyers

Answer 1

• large ocean circulation patterns due to global winds
  - clockwise in Northern Hemisphere, counterclockwise in southern hemisphere
• E to W trade winds between 0-30° push equator current E to W
• Westerlies between 30-60° push mid latitude currents W to E

Question 2

What are upwelling zones?

Answer 2

• Areas of ocean where winds blow warm surface water away from a land mass, drawing up colder, deeper water to replace it
  - Brings O2 and nutrients to the surface which creates productive fishing

Question 3

Explain Thermohaline Circulation

Answer 3

• connects all of the worlds oceans, mixing salt, nutrients, and temperature throughout
  1. warm water from gulf of mexico moves towards North Pole
  2. Cools and evaporates as it moves towards poles
  3. saltier and cooler water at poles is more dense so it sinks and spreads along the ocean floor
  4. rises back up into shallow warm ocean current at upwelling zones

Question 4

Explain ENSO

Answer 4

• El Nino Southern Oscillation
• pattern of shifting atmospheric pressure and ocean currents in the pacific ocean between south america and australia/southeast asia
  - oscillates, or shifts regularly from el nino (warmer, rainier) to la nina (cooler, drier) conditions along coast of South America

Question 5

Compare a regular year, an El Nino year, and a La Nina year

Answer 5

1. Regular Year
   - Trade winds blow equator water East to West
   - Cool H2O upwelled off coast of South America (cool temp = good fisheries)
   - Warm equator current brings heat and precipitation to Australian and Southeast Asia
   - High pressure in east pacific (South America)
   - Low pressure in west pacific (Australia and Southeast Asia)
2. El Nino Year
   - Trade winds weaken, then reverse brining wind from West to East
   - Warm equator current brings heat and precipitation to Americas
   - Suppresses upwelling off coast of South America (decreases fisheries)
   - Cooler, drier conditions in Australia and Southeast Asia
   - High pressure in west pacific (Southeast asia)
   - Low pressure in east pacific (South America)
3. La Nina Year
   - Stronger than normal tradewinds moves the winds West to East too far
   - Increases upwelling off South American coast and brings cooler than normal conditions
   - Warmer and rainier than normal in Australian and Southeastern Asia

Question 6

Effects of El Nino and La Nina

Answer 6

1. El Nino
   - Suppressed upwelling and less productive fisheries in South America
   - Warmer winter in much of North America
   - Increased precipitation and flooding in the Americas (West coast specifically)
   - Drought in Southeast Asia and Australia
   - Decreased hurricane activity in Atlantic Ocean
   - Weakened Monsoon activity in India and Southeast Asia
2. La Nina
   - Stronger upwelling and better fisheries in South America than normal
   - Worse tornado activity in US and hurricane activity in Atlantic
   - Cooler, drier weather in the Americas
   - Rainer, warmer, increased monsoons in southeast asia