El NioSouthern Oscillation

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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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Coupled Walker/Ocean Circulation
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El Niño Conditions
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Relation of Sea Level with SOI
Statistical relationship with SOI Coastal
signals seen in CA Current Ted Strub OSU
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San Francisco Sea Level
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CA Current Effects
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San Francisco Sea Level
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Kelvin Wave Pulse
Kelvin wave pulse Ted Strub OSU
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Santa Barbara Channel - PnB
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Santa Barbara Channel
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Primary Production
hn
CO2
O2
Phytoplankton
Plants
NUTS
Light, carbon nutrients make plants O2
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Santa Barbara Channel
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Santa Barbara Channel
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Santa Barbara Channel Annual Means Oct/Oct
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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 gtgt normal

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Ocean Color 97/98 ENSO Kahru Mitchell 2000
GRL
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More low Chl regions during ENSO
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Fewer occurrences of low SST during ENSO
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Comparisons with the 82-83 ENSO
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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

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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

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El Niño Global NPP
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El Niño Global NPP
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El Niño Global NPP
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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