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El Niño/Southern Oscillation

El Niño/Southern Oscillation. Major climatic perturbation on the planet Coupled atmosphere ocean process Key is the western tropical Pacific Ascending branch of the Walker circulation Potential energy for Kelvin wave pulse www.pmel.noaa.gov/tao/elnino/nino-home.html.

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El Niño/Southern Oscillation

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  1. El Niño/Southern Oscillation • Major climatic perturbation on the planet • Coupled atmosphere ocean process • Key is the western tropical Pacific • Ascending branch of the Walker circulation • Potential energy for Kelvin wave pulse • www.pmel.noaa.gov/tao/elnino/nino-home.html

  2. Coupled Walker/Ocean Circulation

  3. El Niño Conditions

  4. Relation of Sea Level with SOI Statistical relationship with SOI Coastal signals seen in CA Current Ted Strub [OSU]

  5. San Francisco Sea Level

  6. CA Current Effects

  7. San Francisco Sea Level

  8. Kelvin Wave Pulse Kelvin wave pulse Ted Strub [OSU]

  9. Santa Barbara Channel - PnB

  10. Santa Barbara Channel

  11. Primary Production hn CO2 O2 Phytoplankton NUTS Plants Light, carbon & nutrients make plants & O2

  12. Santa Barbara Channel

  13. Santa Barbara Channel

  14. Santa Barbara Channel Annual Means – Oct/Oct

  15. 97/98 ENSO in SB Channel • Deep thermocline & high SST • Limits nitrate supply & chlorophyll biomass • Chl & nitrate are much lower during ESNO • Forcings change • Wind speeds (West channel buoy) are lower • Santa Clara River discharges are >> normal

  16. Ocean Color 97/98 ENSO Kahru & Mitchell [2000; GRL]

  17. More low Chl regions during ENSO

  18. Fewer occurrences of low SST during ENSO

  19. Comparisons with the 82-83 ENSO

  20. 97/98 ENSO in Central CA • Biological processes are much lower • Winds are roughly the same • Upwelling still happens • but it is less “useful” water upwelling

  21. El Niño & CA Current • Kelvin wave pulse propagates north • Propagates 40,000 km in 6 months (2-3 m/s) • Depresses thermocline & raises SST • Thermocline is depressed 30 to 70 m • Winds are not affected in some places not others • Role of thermocline depth is critical • reduced nutrient supply and lower chlorophyll

  22. El Niño & Global NPP

  23. El Niño & Global NPP

  24. El Niño & Global NPP

  25. El Niño & NPP • Global primary production rates are a funtion of thermal stratification • Strong relationship with Multi-ENSO Index (MEI) • MEI is like the SOI • Global NPP is related to ENSO

  26. Ecosystem Regime Shifts - PDO • Climate oscillators besides ENSO • Pacific decadal oscillation - PDO • Ecosystem effects of “regime shifts” • 1977 (have we flipped back??) • Food web & fishery responses

  27. Pacific Decadal Oscillation Warm Cool http://jisao.washington.edu/pdo/

  28. Pacific Decadal Oscillation

  29. Southern Oscillation Index • SOI = Tahiti - Darwin air pressure D’s • Low SOI = El Niño conditions

  30. Pacific Decadal Oscillation

  31. PDO vs. ENSO

  32. Pacific Decadal Oscillation Warm Cool http://tao.atmos.washington.edu/pdo/

  33. Southern Oscillation Index • SOI = Tahiti - Darwin air pressure D’s • Low SOI = El Niño conditions

  34. Pacific Decadal Oscillation

  35. ENSO

  36. Pacific Decadal Oscillation

  37. Coho Pink Salmon Chum Sockeye Chinook

  38. PDO and Salmon Yields September 1972 (National Fisherman 1972) "Bristol Bay [Alaska] salmon run a disaster." "Gillnetters in the Lower Columbia [Washington and Oregon] received an unexpected bonus when the largest run of spring chinook since counting began in 1938 entered the river." 1995 Yearbook (Pacific Fishing 1995) "Alaska set a new record for its salmon harvest in 1994, breaking the record set the year before." "Columbia [Washington and Oregon] spring chinook fishery shut down; west coast troll coho fishing banned."

  39. September 1915 (Pacific Fisherman 1915) "Never before have the Bristol Bay [Alaska] salmon packers returned to port after the season's operations so early." "The spring [chinook salmon] fishing season on the Columbia River [Washington and Oregon] closed at noon on August 25, and proved to be one of the best for some years." 1939 Yearbook (Pacific Fisherman 1939) "The Bristol Bay [Alaska] Red [sockeye salmon] run was regarded as the greatest in history." "The [May, June and July chinook] catch this year is one of the lowest in the history of the Columbia [Washington and Oregon]."

  40. PDO and Fish Yields

  41. PDOand … Mantua et al…

  42. Pacific Decadal Oscillation

  43. PDOand … TABLE 3: Percent change in mean catches of four Alaskan salmon stocks following major PDO sign changes in 1947 and 1977.

  44. PDOand …

  45. Salmon and the PDO • Two Hypotheses for signal • First feeding of smolts entering ocean & PDO_altered primary production • Streamflow alterations drive salmon habitat availability • Consensus is the first feeding…

  46. PDOand …

  47. Bristol Bay Salmon Stocks • Studied / Modeled Extensively • Study concluded Biocomplexity preserved by setting regional guidelines– not just protecting economically viable stock • BUT- where does PDO fit in? The largest harvest of sockeye salmon in the world occurs in the Bristol Bay area of southwestern Alaska where 10 million to more than 30 million sockeye salmon may be caught each year during a short, intensive fishery lasting only a few weeks.

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