The Leeuwin Current in the Southeast Indian Ocean

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The Leeuwin Current in the Southeast Indian Ocean

• Wealth from Oceans Flagship
• Ming Feng
• June 2009

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Leeuwin Current A Warm Surface Current
Sea Surface Temperature

• Anomalous poleward flowing eastern boundary
  current
• Flow rate 1 knot, 300 m deep, counter to
  prevailing southerlies
• Brings warm, tropical waters, and transports
  tropical species

Perth
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Thermocline Signal From Tropical Western Pacific
Transmitted Into the East Indian Ocean
More than 100 meters deeper compared to other two
east boundaries
A 0.5 meter sea level drop in the SE Indian Ocean
14C isotherm depth from WOD
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Low Ocean Production off the west coast

• pilchard population lt 10,000 tons
• Major fishery benthic western rock lobster

Satellite chlorophyll
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Vertical structure of the Leeuwin CurrentLUCIE
Experiment (1986-1987)
Longshore current off Dongara
OFES
Smith et al., 1991
Mooring locations
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Leeuwin Current has the Highest Eddy Energy Among
the Eastern Boundary Currents
Eddies draw energy from work of pressure gradient
Feng, Wijffels, Godfrey, Meyers 2005
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Seasonal Variability Winter Enhancement
Sea level
LC transport
chlorophyll
eddy energy
Feng et al. 2003 Koslow et al. 2008
Jan
Dec
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Response of Lobster Larval Settlement to ENSO
El Nino events
puerulus
Southern Oscillation Index
N. Caputi, WA Fisheries
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Correlation between SOI and altimeter sea level
anomalies
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The Leeuwin Transport is Closely Correlated with
Sea Level Anomalies in Tropical Western Pacific
and Along the Coastal Wave Guides
Correlation Between Leeuwin Transport and Sea
Level Anomalies from ORCA025 Model
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There Are Less Warm Waters Piling in the Western
Pacific and East Indian Ocean
Shallow thermocline anomalies are transmitted
into the East Indian Ocean
Reduction of meridional pressure gradient, which
is the driving force of the Leeuwin Current
Thermocline becomes shallower in the western
Pacific
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Is there a long term decrease of the Leeuwin?

• Volume transport of Leeuwin in NCEP forced models

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ECCO-2
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Downscale the Future Climate on WA Shelf using
OFAM (BLUELink Model)
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Bias in warm pool location and trade winds
Observation
Climate model
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Downscaling using climate model anomalies

• Forcing and initial condition
• ERA40 (1990s climatology)
• Climate Model (2060s, monthly mean)
• Climate Model (1990s climatology)

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Observation
Climate model
Future projection in Climate model
Add climatology from observation and climate
model anomalies
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Change in 0-100m average temperature from 1990s
to 2060s
A slow drift away from climatology a mismatch
between model physical use flux correction?)
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IMOS mooring array northern Australia
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Thank you
CSIRO Marine Atmospheric Research Ming
Feng Physical Oceanographer Phone [phone]
6512 Email ming.feng_at_csiro.au Web
www.cmar.csiro.au
Contact UsPhone 1300 363 400 or 61 3 9545
2176Email Enquiries_at_csiro.au Web www.csiro.au