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Review of Physical Oceanography of the Santa Barbara Channel

Review of Physical Oceanography of the Santa Barbara Channel. Tommy Dickey and Grace Chang University of California, Santa Barbara. RaDyO Planning Meeting San Diego June 6-8, 2007.

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Review of Physical Oceanography of the Santa Barbara Channel

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  1. Review of Physical Oceanography ofthe Santa Barbara Channel Tommy Dickey and Grace Chang University of California, Santa Barbara RaDyO Planning Meeting San Diego June 6-8, 2007

  2. OverviewSetting of the SB ChannelProcesses and Scales Seasonal Flow RegimesTransitional FlowsEddies/Low Freq. WavesKey References

  3. SB Channel Bathymetry * Channel is 40 X 100km * Deep basin in center * Inflow and outflow at east and west ends * Boundaries & complex topography * Complementary obs. ongoing Beckenbach, 2004

  4. Processes and Scales1. Interannual (ENSO)2. Seasonal3. Upwelling events4. Relaxation events (poleward transport)5. Coast. Kelvin waves (large-scale)6. Top. Rossby waves (large-scale) 7. Submesoscale eddies (resonance)8. Tides9. Internal waves10. Surface waves CTW

  5. SB Channel Bathymetry * Channel is 40 X 100km * Deep basin in center * Inflow and outflow at east and west ends * Boundaries & complex topography * Complementary obs. ongoing X X Beckenbach, 2004

  6. Prevailing winds for West Channel Buoy by Month (1994-2002) Beckenbach, 2004

  7. SB Channel Bathymetry * Channel is 40 X 100km * Deep basin in center * Inflow and outflow at east and west ends * Boundaries & complex topography * Complementary obs. ongoing X X Beckenbach, 2004

  8. Prevailing winds for East Channel Buoy by Month (1994-2002) Beckenbach, 2004

  9. Seasonal Cycle of Winds in SB Channel 1993-95 Data Harms and Winant, 2004

  10. Long-term Ave. Currents: HF radar and Moorings Note dominant westward flow along coast, eastward flow adjacent to islands, and cyclonic, convergent flow centered in basin. Flood East – Equatorward flow dom. – Flood West Poleward flow dom. Beckenbach, 2004

  11. Basin-scale Eddy Circulation – Prominent Feature of SB Channel Nishimoto and Washburn, 2002

  12. Seasonal Temp. Along Calif. Coast Beckenbach, 2004

  13. Four Seasonal Current Patterns: Upwelling – Spring Relaxation – Fall, Winter Cyclonic – Summer Horiz. Press. grad, wind stress and curl – dominant? + Large-scale coastally trapped wave Beckenbach, 2004

  14. Six Synoptic Flow Patterns in SB Channel: Summer Spring Fall/Winter Harms & Winant, 1998

  15. Seasonal Cycle of 5-m Currents in SB Channel Seasonal Cycle of 5-m Currents in SB Channel Harms and Winant, 2004 1993-1995 Data

  16. Relaxation Events:Causes of Poleward Flow • Persistent NW winds along the central California coast result in upwelling and cooler coastal water north of Pt. Conception • Weaker flow towards the east Santa Barbara Channel (SBC) results in less upwelling and warmer waters • Water towards the east SBC is typically warmer, less dense, and the undistrubed sea level is higher relative to waters north of Pt. Conception • Strong NW winds ( ~10 – 15 m/s) produce a significant alongshore pressure gradient which opposes the wind direction • When the wind relaxes/reverses due to changes in atmospheric circulation, the pressure gradient force becomes dominant and a strong poleward current develops transporting warm waters north of Pt. Conception Melton & Washburn

  17. SST Satellite Imagery (ºC) Melton & Washburn

  18. Melton & Washburn

  19. Large-Scale Forcing: Waves &Propagating Eddies Beckenbach, 2004

  20. Propagating Eddies: Note: Eddies not very energetic (~15% vel. var.), but do affect flows. Period of ~14 days; prop. Speed ~5 km/day; resonance resp. to CTW’s Beckenbach, 2004

  21. Key ReferencesAnderson et al., 2006, Mar. Ecol. Prog. Ser. Auad, G. & M. Hendershott, 1997, CSRAuad, G. et al., 1999, Prog. in Oceanogr.Beckenbach, E., 2004, UCSB Ph.D. thesisBeckenbach, E. & L. Washburn, 2004, JGRBrink & Muensch, 1986, JGRChen, C.-S. & D.P. Wang, 1999, JGRDiGiacomo, P. & B. Holt, 2001, JGRHarms, S. & C. Winant, 1998, JGRHendershott, M. & C. Winant, 1996, OceanographyMertes, L. et al., 1998, Hydrol. Process. Nishimoto, M. & Washburn, 2002, Mar. Ecol. Prog. Oey et al., 2001, JGROtero & Siegel, 2004, DSR IIWinant et al., 1999, JGRWinant et al., 2003, JGR

  22. For further information,come surfing @ RaDyO link of www.opl.ucsb.eduemail:tommy.dickey@opl.ucsb.edugrace.chang@opl.ucsb.edu

  23. Four Seasonal Current Patterns: Upwelling – Spring Relax .– Fall, Winter Cyclonic, Converg. – Summer Horiz. press-grad, wind stress and curl – dominant? + Large scale coastally trapped waves/eddies Beckenbach, 2004

  24. Upwelling I – Spring Relax .– Fall, Winter Strong NW winds, Upwelling, eastward flow along islands, vel. dir. Offshore of mainland. NW winds weaken or reverse, eastward flow along islands weakens, vel. directed onshore tow. mainland

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