Estuarine Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly

1. Estuarine Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M2 and S2  Monthly M2 and N2  Seasonal (River Discharge)

2. Estuarine Variability Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M2 and S2  Monthly M2 and N2  Seasonal (River Discharge)

3. Tidal Straining Slack Before Ebb Ocean River Tidal Flow Ocean Ebb

4. End of Ebb Tidal Flow Flood

7. z (m) z (m) z (m) z (m) z (m) z (m)

8. Influence of tidal asymmetries in mixing Jay & Musiak (1994) MacCready & Geyer (2010) A A

9. Magnitude (cm/s) of circulation induced by asymmetries in mixing Ratio of circulation induced by asymmetries in mixing vs. density-driven flow

10. Estuarine Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M2 and S2  Monthly M2 and N2  Seasonal (River Discharge)

11. Wind forcing may: produce mixing induce circulation generate surface slopes Subtidal Variability Produced by direct forcing on estuary (local forcing) or on the coastal ocean, which in turn influences estuary (remote forcing - coastal waves)

12. But at the air-water interface it is: Wind-produced mixing The energy per unit area per unit time or power per unit area generated by the wind to mix the water column is proportional to W3 At a height of 10 m, the power per unit area generated by the wind stress is: The wind power at the air water interface is only 0.1 % of the wind power at a height of 10 m. Acts from the surface downward May destratify the entire water column when forcing is large and buoyancy is low

13. s s Weak Depth-Averaged Transport Large Depth-Mean Transport Wind-induced circulation The wind-induced circulation can compete with estuarine circulation, or act in concert The wind-induced circulation will depend on stratification: depth-dependent under stratified conditions weak depth-dependence under homogeneous conditions

16.  x1 sx x2 y x1 x2 x Wind-Induced Surface Slope Can be assessed from the vertical integration of the linearized u momentum equation, with no rotation @ steady state: Note that a westward sx (negative) produces a negative slope. Wind will pile up water in the direction toward which it blows.

18. The perturbation produced by the wind propagates into the estuary and may cause seiching if the period of the perturbation is close to the natural period of oscillation:

19. Estuarine Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M2 and S2  Monthly M2 and N2  Seasonal (River Discharge)

20. Tides in PONCE DE LEON INLET

21. Example: Hudson River

22. Hudson River MacCready & Geyer, 2010, Ann Rev Fluid Mech

23. Fortnightly variability in the Richardson Number

24. Depth Mean or Residual Flow Can you see this modulation from the analytical solution? Ocean Neap Spring Mean or Residual Salinity (Density) Depth Increasing salinity

25. Estuarine Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M2 and S2  Monthly M2 and N2  Seasonal (River Discharge)

28. (Journal of Physical Oceanography, 2007, 2133) Salt Intrusion vs. River Discharge Model

29. 6 5 4 3 2 1 Strong outflow from both River Discharge and NW winds 2 / 3 of volume outflow associated with river input 1 / 3 to wind forcing

31. Forcing from Atmospheric Pressure Gradients Another mechanism that may cause subtidal variability in estuaries comes from atmospheric or barometric pressure.

32. Hurricane Felix  = P/(g) P of 1 mb (100 Pa) =  of 0.01 m

33. Example of Tidal interaction with density gradient Chilean Inland Sea Pitipalena Estuary

34. CTD Time Series 1 2

35. 1 2

36. N C N C C N

37. Slopes produced by different winds in Chesapeake Bay

38. Forcing from Atmospheric Pressure Gradients Another mechanism that may cause subtidal variability in estuaries comes from atmospheric or barometric pressure. B A mouth B head A head mouth depth z Indirectly through sea level slope x