Variation of the Kuroshio in the East China Sea

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Variation of the Kuroshioin the East China Sea

• Magdalena Andres
• Ocean Sciences OS 54B-05
• February 24, 2006

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North Pacific
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East China Sea
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Instrumentation Dec. 2002 Nov. 2004
Inverted echo sounder Hourly measurements
of travel-time pressure bottom currents
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700 dbar as the reference Baroclinic Velocity
0 m/s at 700 dbar Barotropic Velocity Absolute
Velocity at 700 dbar
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Travel time as a proxy for T, S, d profiles

• Historical data 1720 casts

• Measured T, S, P ?
• simulated travel time

• Generate lookup-table relates
• travel time to vertical T and S profiles

• Hydrocast data from North Pacific Hydrobase
  Macdonald et al., 2001 and Nagasaki Marine
  Observatory (NMO), Japan Meteorological Agency

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Baroclinic velocity
Vertical r profiles ? horizontal r gradients
thermal wind equations ? baroclinic velocity
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Baroclinic Transport (referenced to 700 dbar)
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Bottom Currents
V
Mean V
U
-2 cm/s
C1
-3 cm/s
C6
C2
C3
C4
12 cm/s
V
N
-1 cm/s
U
-3 cm/s
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Absolute Velocity
Mean16.6 Sv std 3.3 Sv range 7.3 Sv to
24.9 Sv
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What does including the barotropic component tell
us?

• There is often a sub-surface velocity core
• 200 m deep
• 75 km east of shelf break

• Positive velocities reach down to the seafloor

• There is a persistent recirculation east of the
  Kuroshio

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Conclusions

• Mean Baroclinic Transport 17.0 Sv (std 2.7 Sv)
  range 9.2 to 23.8 Sv

• Mean Absolute Transport
• 16.6 Sv (std 3.3 Sv)
• range 7.3 to 24.9 Sv

• Including the barotropic component doesnt change
  the Transport much does change the picture of
  horizontal current shear.

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Comparison to other work
16.6 Sv
Preliminary evaluation of ADCPs on the shelf
5 Sv (B.-H. Lim, OS54B-06)
22 Sv
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Future work
Add transports determined with inverted echo
sounders line transports to ADCP transport to get
complete Kuroshio Transport in ECS Compare
Kuroshio Transport to 1) Flow into the
Japan/East Sea 2) Flow through the Tokara
Strait 3) Ryukyu Current 4) Approach of
mesoscale eddies off of Taiwan
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Acknowledgements

• Jeff Book
• Gerry Chaplin
• Kyung-Il Chang
• Kathy Donohue
• Andy Greene
• Hiroshi Ichikawa
• Byung-Ho Lim
• Doug Mitchell
• Jae-Hun Park
• Karen Tracey
• Randy Watts
• Mark Wimbush
• Crew and students aboard the T/V Kagoshima-maru