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April 2013

Subsurface Tidal-Period Currents in the Upper Reaches of the Monterey Submarine Canyon and nearby Continental Shelf. A draft overview of some of what we know. Prepared by Erika McPhee-Shaw for Tenera Environmental. April 18, 2013. .

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April 2013

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  1. Subsurface Tidal-Period Currents in the Upper Reaches of the Monterey Submarine Canyon and nearby Continental Shelf. A draft overview of some of what we know. Prepared by Erika McPhee-Shaw for TeneraEnvironmental. April 18, 2013.

  2. MLML Intake pipe at ~ 17-m depth (sand changes so depth varies) - just offshore of Moss Landing near MLML pumphouse and MBARI April 2013 We do not measure current velocity explicitly. But the repeated 12-hour cycles give a good idea of the kind of bulk transport, swashing back and forth, that occurs every day.

  3. How far away does that water come from, and how far away does it go back to? (What is the excursion distance of that “sloshing?”) Cold temperatures and low oxygen values at shore found on average at depths of > 60 m offshore at the MBARI M1 mooring. Ashley Booth, MLML thesis, 2010.

  4. However the “source depth” is highly variable over the shelf.(NSF Shelf Benthic Exchange Events Project, McPhee-Shaw, MLML, Shaw and Stanton, NPS, Bellingham, MBARI) - ……. Not as sure about the canyon…….. October 2011 70 to 20 m May 2011. 20 to 10 m

  5. Washburn and McPhee-Shaw, submitted to Oceanography, April 2013.

  6. What kinds of currents are associated with this “sloshing?” These profiles show the 2-layered nature of the currents during a 10-day interval when the internal tide dominated flow conditions From Cheriton et al., manuscript in prep. NSF BEX, October 2011 data Current amplitudes: ~ 20 cm/s Southern MB Shelf

  7. What kinds of currents are associated with this “sloshing?” From Tenera. MBARI M0 mooring. 75-m depth. Deployed ~ 2005 to 2010 (?) Separate Analysis Current amplitudes: ~ 20 cm/s Northern MB Shelf

  8. What kinds of currents are associated with this “sloshing?” On shelf, currents are typically a bit stronger at surface. But in the canyon, at all depths, currents are more intense closer to the seafloor Current amplitudes: ~ 50 to 80 cm/s, in canyon, near bottom. (mooring at 250 m. From Xu et al., 2008), Current amplitude not related to spring-neap tides.

  9. And here are currents even deeper in the canyon. Shows that a lot of the internal tide energy is trapped along the bottom 300 meters out there – as it shoals this energy takes up a greater portion of the water column, but does not have that two-layered structure out deep. Some data from mooring at 1100 m Velocity magnitude profiles from two ADCPs NSF Canyon Mixing and Boundary Interior Exchange Project, Girton, McPhee-Shaw, Kunze. Current amplitudes: ~ 40 to 60 cm/s, in canyon, near bottom. (Mooring at 1100 m. K. Morrice MLML Thesis 2010. )

  10. Scales of back-and-forth excursions associated with this sloshing?

  11. 30 m 60 m 90 m North ADCP South ADCP Slide from Joe Phelan Source Water Body modeling • Two water bodies concept. • Deep canyon ‘wedge’ (red) which essentially moves along an east/west axis. Derived from canyon ADCPs. • A shelf body (grey) driven by surface currents. Derived from CODAR data combined with shelf and deep water ADCPs. M0 (deep water) 10 km or 2 km? Shelf ADCP

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