Oceanic Response to Overflows

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Oceanic Response to Overflows

• Shin Kida
• MIT/WHOI Joint Program
• November 10, 2004

Advisors Jim Price and Jiayan Yang
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Overflow and oceanic water are dynamically
connected.

• My goal is to examine how the ocean responds to
  overflows. This consists of layer interaction and
  mixing.
• Layer interaction was examined by not allowing
  any mixing process

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Model Setup

• HIM,2-layer model.
• Dense water formation in the upper basin.
• Physical space is close to the Faroe Bank Channel
  Overflow
• Depth of the sill D1000m
• Topographic slope a0.01
• Reduced gravity g0.005 m/s2
• Outflow transport 2Sv

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Snap Shot
Ekman number n/f 7.5e-6/1.4e-4 0.05 lt 0.15
(model) Momentum to upper layer
Strong eddies! roughly 20 cm/s
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Current Meter
upper layer
lower layer
Lower layer velocity is always downstream Strong
Background Flow
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By only changing the upper layer thickness
H1000m
H2000m
Increasing the layer thickness prevents
baroclinic instability. This reduces the momentum
transfer to the upper layer and thus can not
drive a significant circulation in the upper
layer.
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Time average
upstream 0.25
downstream 0.05
Momentum transfer is done locally where the flow
is unstable. This drive the upper layer
flow. Downstream shows that the eddies flow
according to the Ekman number.
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• Adiabatic overflow and ocean interaction is also
  important!
• Changes the dynamics of the overflow itself
• More wave like than a tube.
• Steeper angle than the Ekman number shows the
  momentum loss to the ocean.
• This momentum transfer is significant enough to
  drive eddies of strength 20cm/s and a mean flow
  of 10cm/s in the ocean layer.