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Temporal Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M 2 and S 2  Monthly M 2 and N 2  Seasonal (River Discharge)

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Presentation on theme: "Temporal Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M 2 and S 2  Monthly M 2 and N 2  Seasonal (River Discharge)"— Presentation transcript:

1 Temporal Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M 2 and S 2  Monthly M 2 and N 2  Seasonal (River Discharge)

2 Estuarine Variability  TidalTidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M 2 and S 2  Monthly M 2 and N 2  Seasonal (River Discharge)

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

4 End of EbbFlood Tidal Flow Animation of Shear Instability

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

6 1 2 CTD Time Series

7 1 2

8 Example of Tidal Straining

9 Maximum stratification at the end of ebb

10 Dynamically, tidal motion modifies the mean value of bottom friction. where u b is the instantaneous bottom velocity The mean value of the bottom stress over a tidal cycle is: Considering that the flow u may be represented as Bottom friction depends then on the tidal current amplitude.

11 Another dynamical implication of tidal flows is the generation of a mean non-linear term: because The tidal stress is independent of z as is the barotropic pressure gradient. e.g. Tidal stresses tend to operate with the barotropic pressure gradient. The mean over a tidal cycle of is: 0

12 Estuarine Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M 2 and S 2  Monthly M 2 and N 2  Seasonal (River Discharge)

13 Subtidal Variability Produced by direct forcing on estuary (local forcing) or on the coastal ocean, which in turn influences estuary (remote forcing - coastal waves) Wind forcing may:produce mixing induce circulation generate surface slopes 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 W 3 At a height of 10 m, the power per unit area generated by the wind stress is: But at the air-water interface it is: The wind power at the air water interface is only 0.1 % of the wind power at a height of 10 m.

14 Forzamiento por viento Perfil típico de velocidad neta boca cabeza Perfil con viento hacia la boca boca cabeza Viento Perfil con viento hacia la cabeza boca cabeza Viento profundidad Depende de la estratificación de la columna de agua

15 Ejemplo Estrecho de Meninea en Canal Moraleda (combinando forzamiento por marea, viento, presión)

16 Ejemplo Meninea (combinando forzamiento por marea, viento, presión) También produce oscilaciones en la picnoclina ==  resonancia

17 Wind-Induced Surface Slope Can be assessed from the vertical integration of the linearized u momentum equation, with no steady state: Note that a westward  sx (negative) produces a negative slope.  sx x1x1 x2x2 y x x1x1 x2x2  Wind will pile up water in the direction toward which it blows.

18 Slopes produced by different winds in Chesapeake Bay

19 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:

20 Forzamiento por Gradientes de Presión Atmosférica BA boca cabeza Indirectamente a través de pendiente de nivel del mar cabeza profundidad B A boca x z

21 Another mechanism that may cause subtidal variability in estuaries comes from atmospheric or barometric pressure.

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24 Estuarine Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M 2 and S 2  Monthly M 2 and N 2  Seasonal (River Discharge)

25 Tides in Panama City

26 (JGR, 1982, 87(C10), 7985)

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29 Thomson et al. (2007, JGR, 112, C09022)

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

34 Estuarine Variability  Tidal  Subtidal Wind and Atmospheric Pressure  Fortnightly M 2 and S 2  Monthly M 2 and N 2  Seasonal (River Discharge)

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36 (JGR, 1982, 87(C10), 7985)

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38 N C NC NC

39 Axial Distributions of Salinity Spring 1999 Fall 1999 H M HM HM

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