Estuarine Circulation and Mixing

"...to be summa cum laude in estuarine productivity, there must be circulation. A good mix, one is tempted to say, is almost everything. Not just in one direction. There should be two-layered or horizontal circulation in which heavier salt water from the ocean slides under the lighter and fresher surface water from rivers. Inexorably, that is, with a net flow upstream on the bottom and downstream on the top which surmounts the temporary effects of wind and tide. Ideally, there should also be some vertical mixing, which is not found in every estuary, since it requires significant contrasts in depths and water temperatures." from Beautiful Swimmers: Watermen, Crabs and the Chesapeake Bay, by William W. Warner.

SYLLABUS:

(Jan. 4) Introduction: What estuaries are like and why

• Class organization, estuary and fjord definitions, water quality and habitat issues.
• Geomorphology: how do estuaries evolve over interglacial time scales (erosion, deposition, sea level rise, biological effects)? Classification: the range of observations and the quest for simple explanations.
• Simple mass and salt conservation: Knudsen's Relation
• Dyer (1997) Estuaries: A Physical Introduction, pages 1-22

(Jan. 11) Tides

• Definitions, Celestial Forcing, Equilibrium Tides.
• Solutions in bays (1/4 wave oscillator)
• Tidal excursion, ellipse, prism.
• Spring and neap: effects of multiple frequencies.
• Effects of friction and non-linearity: ebb and flood dominance, phase shifts, residuals, and overtides.
• Lavelle et al. (1988) Model of Puget Sound Tides
• Mofjeld and Larsen (1984) Observed Puget Sound Tides (RQ)
• Lab Demo: Quarter-Wave Resonance, Particle Motion in Waves

• Wednesday: Jan Newton, WA State Dept. of Ecology: Puget Sound Water Quality Issues
• Friday: Open discussion (many students gone to Student PO Retreat at Friday Harbor)

(Jan. 25) Turbulence: Vertical Fluxes of Momentum and Buoyancy

• Microstructure Measurement
• Boundary layers, log layer, drag coefficient, wind stress
• Tidal Mixing
• Critical Richardson Number
• Seim and Gregg (1994) Admiralty Inlet Mixing

• One- and 2-Layer Hydraulics
• Strait of Gibraltar
• Bosporus to Black Sea
• Wesson and Gregg (1994) Gibraltar
• Geyer and Cannon (1982) Deep Water Renewal in a Fjord

(Feb. 8) Baroclinic Forces: the Exchange Flow and Salt Balance

• Baroclinic forces and frictionally arrested solutions
• Feedback: the salt balance vs. the exchange flow
• Tidally-averaged 'complete' solutions
• Hansen and Rattray (1965, 66)
• Lab Demo: Two-Layer Flow Over a Sill
• Lab Demo: Estuarine Circulation (River + Tidal Mixing = Exchange Flow)

(Feb. 15, no Monday) Coastal Plain Estuaries

• Chesapeake Bay
• Tyler and Seliger (1989) Bio-physical Interactions
• Carter and Pritchard (1988) Chesapeake Overview
• Dyer (1997), Chapter 9.

(Feb. 22) Fjords

• Puget Sound
• Cokelet et al. (1991) Pollution Ages in PS
• Ebbesmeyer et al. (1988) PS Overview
• Lavelle et al. (1991) Dense Flow over Admiralty Inlet
• Dyer (1997), Chapter 8.
• Lab Demo: Puget Sound Model in OOB

(Mar. 1) Well-Mixed Estuaries, Salt Wedges, and Other Effects

• San Francisco Bay
• Conomos et al. (1985) SF Bay Overview
• Walters et al. (1985) Time Scales of Flow in SF Bay

• Fraser River, Colombia River
• Geyer and Farmer (1989)
• Hughes and Rattray (1980)

• Channel Shape, Headlands, Coriolis, Fronts
• Signell and Geyer (1988) Tidal Flow around a Headland

• Gregg: Observational Techniques
• MacCready: Theoretical and Numerical Models

(Mar. 15) Finals week (no class)

Class Notes

Required text: Dyer, K. R., 1997: Estuaries, A Physical Introduction, 2nd Edition. John Wiley & Sons, Chichester, 195 pp. This should be available in the University Bookstore (it's not very expensive). Also, get yourself a copy of the local "Tide Guide", just $2 near the checkout counter at the South Campus Center Bookstore.

This class is intended to be of use to graduate students from all the sciences. While familiarity with fluid mechanics and differential equations is useful, it is not required. If there are widely disparate backgrounds, we may make different versions of the problem sets. The reading essays are in the form of a "Reading Question" (RQ), where the student is asked to formulate (and attempt to answer) a detailed question based on reading of a scientific paper. This in intended as practice in analytical, critical reading and writing. Detailed comments will be given on each student's essays.

Grading Policy

This course is only to be taken for a grade. Grades will be based on problem sets (50%), and essays on the reading (50%). There will be no final exam.

If you would like to request academic accommodations due to a disability, please contact Disabled Student Services, 488 Schmitz, 543-8924 (V/TDD). If you have a letter from Disabled Student Services indicating you have a disability that requires academic accommodations, please present the letter to either of us so we can discuss the accommodations you might need for class.

References:

• Cameron, W. M., and D. W. Pritchard, 1963: Estuaries. In: The Sea (Ed. M. N. Hill), Vol. 2, Wiley, New York, 306-324.
• Carter, H. H. and D. W. Pritchard, 1988: Oceanography of Chesapeake Bay. Hydrodynamics of Estuaries: II Estuarine Case Studies, B. Kjerfve, Ed., CRC Press, 1-16.
• Cokelet, E. D., R. J. Stewart, and C. C. Ebbesmeyer, 1991: Concentrations and ages of conservative pollutants in Puget Sound. Puget Sound Research '91, Vol. 1, Puget Sound Water Quality Authority, 99-108.
• Conomos, T. J., R. E. Smith, and J. W. Gartner, 1985: Environmental setting of San Francisco Bay. Temporal Dynamics of an Estuary: San Francisco Bay, J. E. Cloern and F. H. Nichols, Eds., Dr. W. Junk Publishers, Kluwer Academic, 1-12.
• Dyer, K. R., 1997: Estuaries, A Physical Introduction, 2nd Edition. John Wiley & Sons, Chichester, 195 pp.
• Ebbesmeyer, C. C., J. Q. Word, and C. A. Barnes, 1988: Puget Sound: a fjord system homogenized with water recycled over sills by tidal mixing. Hydrodynamics of Estuaries: II Estuarine Case Studies, B. Kjerfve, Ed., CRC Press, 17-30.
• Geyer, W. R. and G. A. Cannon, 1982: Sill processes related to deep water renewal in a fjord. J. Geophys. Res., 87, 7985-7996.
• Geyer, W. R. and D. M. Farmer, 1989: Tide-induced variation of the dynamics of a salt wedge estuary. J. Phy. Oceanogr., 19, 1060-1072.
• Hansen, D. V., and M. Rattray, 1966: New dimensions in estuary classification. Limnol. Oceanogr., 11, 319-326.
• Hughes, R. P., and M. Rattray, 1980: Salt flux and mixing in the Columbia River Estuary. Est. Coast. Mar. Sci., 10, 479-494.
• Lavelle, J. W., E. D. Cokelet, and G. A. Cannon, 1991: A model study of density intrusions into and circulation within a deep, silled estuary: Puget Sound. J. Geophys. Res., 96, 16 779-16 800.
• Lavelle, J. W., H. O. Mofjeld, E. Lempriere-Doggett, G. A. Cannon, D. J. Pashinski, E. D. Cokelet, L. Lytle, and S. Gill, 1988: A multiply-connected channel model of tides and tidal currents in Puget Sound, Washington and a comparison with updated observations. NOAA Tech. Memo. ERL PMEL-84, Pacific Marine Environmental Laboratory, NOAA.
• Mofjeld, H. O. and L. H. Larsen, 1984: Tides and Tidal Currents of the Inland Waters of Western Washington. NOAA Tech. Memo. ERL PMEL-56, Pacific Marine Environmental Laboratory, NOAA.
• Seim, H. E. and M. C. Gregg, 1994: Detailed observations of a naturally occurring shear instability. J. Geophys. Res., 99, 10 049-10 073.
• Signell, R. P., and W. R. Geyer, 1990: Numerical simulation of tidal dispersion around a coastal headland. Residual currents and long-term transport, R. T. Cheng, Ed., Springer-Verlag, 210-222.
• Tyler, M. A., H. H. Seliger, 1989: Time scale variations of estuarine stratification parameters and impact of the food chains of the Chesapeake Bay. In Estuarine Circulation, B. J. Neilson, J. Brubaker and A. Kuo, Humana Press, Clifton, NJ, 201-233.
• Walters, R. A., R. T. Cheng, and T. J. Conomos, 1985: Time scales of circulation and mixing processes of San Francisco Bay waters. Temporal Dynamics of an Estuary: San Francisco Bay, J. E. Cloern and F. H. Nichols, Eds., Dr. W. Junk Publishers, Kluwer Academic, 13-36.
• Wesson, J. C., and M. C. Gregg, 1994: Mixing at Camarinal Sill in the Strait of Gibraltar. J. Geophys. Res., 99, 9847-9878.