Wind Driven Circulation in the California Current

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Wind Driven Circulation in the California Current

• Seasonal changes of equatorward winds drive
  circulation of the CA Current
• Winds alter offshore Ekman transports
• This in turn drives upwelling processes
• AND geostrophic flows

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Seasonal Wind Stress
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Seasonal Wind Stress
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Coastal Upwelling
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Coastal Upwelling

• Equatorward winds along a coastline lead to
  offshore Ekman transport
• Mass conservation requires these waters replaced
  by cold, denser waters
• Brings nutrients to the surface increasing rates
  of primary production
• Creates dynamic height gradients - currents

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Coastal Upwelling
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CalCoFI Cruise 9804
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Coastal Upwelling Changes Density
Line 90
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Density Currents for Line 90
Negative currents to south
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CalCoFI Grid
Lynn Simpson 1987 Reading is on-line
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Seasonal Circulation
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CalCoFI Grid
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10 year time series _at_ Monterey Bay
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Seasonal Cycle _at_ Monterey Bay
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Currents in Monterey Bay
To North
To South
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Seasonal Circulation
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A Tilting CA Current??
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Seasonal Circulation
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Seasonal CA Current Circulation
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Seasonal CA Current Circulation
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Seasonal Circulation
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Mean California Current

• Seasonal changes in winds drive the seasonal
  intensification of the CA Current
• CA Current is highest in spring/summer
• Seasonal change are due to a tilting of sea
  surface
• Slack winds correspond to an inshore counter
  current or Davidson Current

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Mean California Current

• Inshore counter current appears to be connected
  to the CA undercurrent
• Deepest when upwelling is highest
• Shallow when winds relax
• Southern California Eddy
• Kind of like flow over a step
• Occurs in the fall