1. Chapter 5—Part 1 Ocean Circulation/ Upwelling Zones/ El Niño

2. Ocean Circulation 1. Eckman spiral 2. Upwelling zones 3. El Niño

3. Ocean surface currents are driven by atmospheric winds Energy from wind transferred to water by friction

4. Wind Wind moves surface water (friction) Velocity of water decreases with depth

5. But Both the wind and the ocean currents are deflected near the atmosphere-ocean interface by a combina- tion of the Coriolis effect, friction, and gravity This gives rise to what is termed the Eckman Spiral - Surface wind rotated 45 o relative to the geostrophic (free troposphere) wind - Surface waters move 45 o relative to the surface wind direction - Net transfer of water 90 o to the surface wind

6. The Eckman Spiral

7. Surface waters move 45 o relative to surface wind Net transfer of water 90 o to surface wind direction Eckman Pumping Equator Surface wind Surface current Net ocean transport Surface water is driven offshore by Eckman spiral Replaced by water from below  upwelling! Geostrophic wind (Easterlies)

8. Consequences of upwelling Deep water is rich in nutrients (P, N, Fe) Upwelling brings nutrient-rich water to the surface ocean, fueling biological productivity (phytoplankton) Zooplankton eat the phytoplankton Fish eat both of these  get good fisheries in upwelling zones

9. El Niño (the Christ child) Every 3-7 years Last 6-18 months Happens near Christmas season

10. El Niño (the Christ child) Every 3-7 years Last 6-18 months Happens near Christmas season Opposite: La Niña (the girl child)

11. Normally… Warm waters pushed by trade winds towards Asia and Australia Cold waters upwell near South America

12. http://www.ldeo.columbia.edu/dees/ees/climate/slides/ocean_index.html Pacific warm pool

13. Normal Conditions: http://www.enn.com/specialreports/elnino/what.asp This east-west circulation pattern, which is sort of like a Hadley cell, is called the Walker Circulation It reinforces the normal tropical easterlies, thus helping to foster upwelling off the coast of Peru Australia/ Indonesia South America

14. Normal Conditions: El Niño Condition: http://www.enn.com/specialreports/elnino/what.asp Normal Walker Circulation Weakened Walker Circulation South America Australia/ Indonesia Australia/ Indonesia

15. Atmospheric Pressure: Normal high over Tahiti, low over Darwin, Australia El Nino low over Tahiti, high over Darwin The shift in pressure is called the Southern Oscillation The combined El Niño/Southern Oscillation is referred to as ENSO

16. Atmospheric Pressure: Normal high over Tahiti, low over Darwin, Australia El Niño low over Tahiti, high over Darwin * Darwin

17. Southern Oscillation Index [ P diff - P diffav ] SOI = 10 ----------------------- SD(P diff ) where P diff = (average Tahiti MSLP for the month) – (average Darwin MSLP for the month), P diffav = long term average of P diff for the month in question, and SD(P diff ) = long term standard deviation of P diff for the month in question. http://www.bom.gov.au/climate/glossary/soi.shtml

18. Strong El Nino

20. La Niña http://www.bom.gov.au/climate/current/soi2.shtml Is this what is caused the 2011 Texas drought? “ENSO neutral” conditions persisted during most of 2012

21. The fact that we have been in an extended La Niña may explain why the climate has not warmed as fast as expected over the past 15 years…

22. Total heat accumulation in sea, land, and air http://www.skepticalscience.com/clarifying- continuation-global-warming.html

23. Results of El Niño In the Pacific Region: weaker trade winds warm waters across the Pacific rain in South America, drought in Australia

24. Results of El Niño In the Pacific Region: weaker trade winds warm waters across the Pacific rain in South America, drought in Australia Teleconnections--shifting atmospheric patterns (global) high rain in the US midwest more storms in the Pacific, fewer in the Atlantic heavy rains in California cold winters in the Northeastern US