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Swiftsure 2012 Tidal Currents

Swiftsure 2012 Tidal Currents. Richard Dewey RVYC / UVic http://canuck.seos.uvic.ca/SwiftsureTides2012/ Swiftsure_2012_Tides.html rdewey@uvic.ca. Tidal Heights and Currents. Tidal currents “flood” in from the ocean on a rising tide and “ebb” out to the ocean on a falling tide.

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Swiftsure 2012 Tidal Currents

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  1. Swiftsure 2012Tidal Currents Richard Dewey RVYC / UVic http://canuck.seos.uvic.ca/SwiftsureTides2012/ Swiftsure_2012_Tides.html rdewey@uvic.ca

  2. Tidal Heights and Currents Tidal currents “flood” in from the ocean on a rising tide and “ebb” out to the ocean on a falling tide. Tidal currents are driven by hydrostatic pressure and flow down slope from higher to lower water.

  3. Tides in Northeast Pacific M2 Co-Phase

  4. Tides in Juan de Fuca • Tides in Juan de Fuca Strait are forced primarily from the tidal wave (not tsunami) propagating northward up the coast of Washington and BC. • Further in-land (Strait of Georgia/Puget Sound), the “wave” also reflects and becomes more complicated.

  5. Surface Slope Drives Tidal Currents • High water (high tide) represents high hydrostatic pressure, low water (low tide) low hydrostatic pressure. • Water flows from high to low water, down slope. • Sailors needn’t worry too much about tidal height, except when anchoring or rock hopping. • The local current patterns are determined by the large scale basins and channels.

  6. Deep vs Shallow Tidal Currents • Deep water has more inertia, will ride “up-hill” to stop,  reversals are lagged/delayed. • Shallow and boundary layer flows have more friction, can be slower & will reverse sooner. • Lateral convergence or vertical shoaling can cause accelerated flows.

  7. Tidal Stations: Currents Port Renfrew Victoria Juan de Fuca West Race Passage and Juan de Fuca East

  8. Reading Tidal Current Tables Victoria PDT=PST+1

  9. Tidal Current Station Tidal Height Station

  10. Tides May 28 – 29, 2011 Start Rounding Finish

  11. Reading Tidal Current Tables Race Passage PDT=PST+1

  12. Tidal Current Station

  13. Tides May 28 – 29, 2011 Start Rounding Finish

  14. Tidal Model Foreman et al., (2004)

  15. Tides May 28 – 29, 2011 Start Rounding Finish

  16. Tidal Currents Summary • Heights only tell part of story • Currents driven by surface slope • Deep water has inertia: tide changes are delayed • Shallow water is frictional: slower, tide changes are more immediate, convergence accelerates flow • Race Passage: Shallow (immediate), Funnel (strong) • Tide tables: • Race Passage (boundaries and near start/finish) • Juan de Fuca East (central east) • Juan de Fuca West/Entrance (central west)

  17. Good Luck! http://canuck.seos.uvic.ca/SwiftsureTides2012/ Swiftsure_2012_Tides.html rdewey@uvic.ca http://www.charts.gc.ca/ publications/ctct-tmcc-eng.asp

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