1. 하구및 연안생태Coastal management
2015 년 가을학기

2. Circulation modes Classic view: two layered
Net outflow in surface
Net inflow in the bottom
6 circulation modes (Elliott, 1976)
Classical
Reverse
3 layered
Reverse 3 layered
Discharge
Storage

3. Circulation modes Potomac Complex spatial and temporal variability
43 % classic
22% storage
21% reverse
7% reverse 3 layered
6% discharge
1% 3 layered
Complex spatial and temporal variability
Lateral variability is more complex

4. Far field effects Large scale meteorological forcing Kelvin waves
Continental shelf waves
Coastal trapped waves
periods: 2~15 days, length 1000km, wave heights: less than 0.8 m
Free-propagation
Ecological importance of non local effects
Submergence of tidal flat
Biased measurement; need to check the non local forcing
Turbidity maximum
salinity

5. Estuarine mixing Mixing Salinity as a mixing indicator
Adjectives; longer time scale
Dispersive: shorter
Salinity as a mixing indicator
Conservative
ocean is only source (35 versus 0.6 ppt)
Easy and inexpensive to determine; does not need great precision

6. Dispersive mixing Scattering of water parcels
Tidal sloshing; time averaged flux of particles: dominant
Transport = Velocity x concentration
Integral seldom vanishes because the phase differences currents and concentration
Shear effects
Systematic covariation of velocity and particle concentration
Depth
Width
Cross section
Eddy diffusion: not important (>> molecular diffusion)
Molecular diffusion; negligible
Tidal trapping; temporarily trapped in shoreline indentations released by tidal currents and replaced with new water mass

7. Forces for mixing Tidal forcing Fresh water
Advective mixing: tidal pumping
Dispersive mixing: sloshing shear trapping
Fresh water
Buoyancy; density difference, gravitational circulation advective mixing
Temporal variations of mixing in a estuary
Spring tide; enough currents to break stratifications

8. Mixing diagram Salinity versus material
Can determine if the material is “source” or “sink”
Assumptions
One-dimensional (longitudinal) mixing
Quasi steady state
All data are averaged over one or more complete tidal cycles
Concentration in fresh water and ocean can change over time; cause problem!!!

9. Dynamic classification
A: highly stratified; lower mississippi
Low tidal range
Moderate or high discharge
B: Partially mixed
Chesapeake Bay
2~10 ppt difference vertically
Gravitational circulation is typical
Moderate or high tide and moderate discharge
C: Well mixed; large tidal range, little fresh water
C1: vertically homogeneous with laterally reversing net flow
C2: vertically, laterally homogeneous

11. Estuary modification Dredging Widening
Make it deeper
ABC
Widening
Damming of river; reduced discharge

12. Circulation-stratification diagram
Hansen and Rattry (1965)
Stratification: salinity difference between surface and bottom S/S0
Circulation: “net surface flow”/”fresh water flow”
Net surface flow : average of one tidal cycle
Fresh water flow: discharge / area

13. Circulation-stratification diagram
Class 1: lagoon, bar built
Class 2: partially mixed
Class 3: fjord and fijard; advective mixing
Class 4: type A; strongly stratified.