Anthropogenic Change in the North Pacific

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Anthropogenic Change in the North Pacific

• John C. Fyfe

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Topics

• Aleutian Low change and impact on North American
  temperature
• Oceanic Rossby wave speed-up and impact on El
  Niño frequency

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Winter Sea-Level Pressure
H
H
L
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• Datasets
• UKMO HadSLP2
• CRUTEM3v surface temperature
• ECMWF ERA-40 reanalyses

• Simulations
• WCRP CMIP3 multi-model ensemble
• 15 Models (multiple realizations)
• Control, historical and projected

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Fyfe, 2009
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SLP Trends (hPa/century)
CI 0.5
CI 0.5
Fyfe, 2009
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Fyfe, 2009
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Fyfe, 2009
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Fyfe, 2009
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Conclusions 1

• Anthropogenic shift toward a deeperand more
  poleward Aleutian Low
• Explaining about half of the surface warming over
  Western North America

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Oceanic Rossby Waves
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Chelton and Schlax, 1996
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White et al., 2004
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IPCC AR4 Report, 2007
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• Question
• Is warming (increasing stratification) causing
  these waves to speed up?

• Simulations
• CCCma Global Climate Model
• Control, historical and projected

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For each 20-year period solve
Capotondi and Alexander, 2001
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Correlation between actual and computed h
Fyfe and Saenko, 2007
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Fyfe and Saenko, 2007
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Propagation speed at 14ºN
Fyfe and Saenko, 2007
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Propagation speed change
Fyfe and Saenko, 2007
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Producing more frequent El Niños?
Merryfield, 2006
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Conclusions 2

• Anthropogenic speed-up of oceanic Rossby waves
  with ocean warming
• Possibly leading to more frequent El Niños in
  the future

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Anthropogenic Change in the North Pacific

• John C. Fyfe