THE INTERNAL TIDAL BORE AT THE HEAD OF THE MONTEREY SUBMARINE CANYON: 23 FEBURARY 2003

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THE INTERNAL TIDAL BORE AT THE HEAD OF THE
MONTEREY SUBMARINE CANYON 2/3 FEBURARY 2003

• LEUT Kristen Watts, RAN
• OC 3570
• Winter 2003

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Data for Report

• Collected on Leg II of the cruise, in the
  vicinity of the head of Monterey Canyon
• 25-hour CTD Time Series
• ADCP Measurements

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Data for Report
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Data for Report

• Collected on Leg II of the cruise, in the
  vicinity of the head of Monterey Canyon
• 25-hour CTD Time Series
• ADCP Measurements
• 2 x Aquadopp Current Meters

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Purpose

• To examine the three datasets to observe the
  processes operating at the head of the canyon.
• Shows evidence of the passage of an internal
  tidal bore.

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Tidal Bores

• Many studies have previously been conducted in
  the Monterey Canyon to investigate the internal
  wave pattern and the internal tidal bores, at the
  canyon head.
• A bore is an unsteady flow, often caused by tidal
  forcing and can be equated to a moving hydraulic
  jump.

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Tidal Bores
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Tidal Bores
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Internal Tidal Bores

• Exists where
• a submarine canyon forms a converging funnel
  shape,
• combined with a gently rising sea floor,
• preferably over a considerable distance.

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Monterey Canyon
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Bathymetry of the Canyon
CTD
Current Meters
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Data Analysis
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HW 1011
HW 0024
LW 0412
LW 1742
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Discussion

• According to literature, the arrival of an
  internal tidal bore is characterised by
• wave steepening,
• a sharp drop in temperature and salinity over the
  water column, and
• a significant increase in upslope current
  velocity at the bottom.

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TIDAL BORE
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Standing Wave
Instead of continuing past the barrier, the wave
is reflected
Incident Wave
With reflection, there is a 1800 phase change,
flipping the wave over so that it interferes
constructively with the incident wave.
Reflected Wave
Resultant Wave
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Propagating Internal Wave
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Standing Internal Wave
Onset of Bore East/West Velocity 0
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Conclusion

• The passage of an internal tidal bore was evident
  from the collected data.
• The tidal bore appears in the form of a standing
  internal wave.
• Further research with a longer time series and
  more stations would be needed to completely
  understand this process.

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Questions?