Temporal Variability Tidal Subtidal Wind and Atmospheric Pressure

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

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

Tidal Straining Slack Before Ebb River Tidal Flow Ebb Ocean

End of Ebb Tidal Flow Flood Animation of Shear Instability

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

CTD Time Series 1 2

1 2

Example of Tidal Straining

Maximum stratification at the end of ebb

Dynamically, tidal motion modifies the mean value of bottom friction. where ub 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.

Another dynamical implication of tidal flows is the generation of a mean non-linear term: The mean over a tidal cycle of is: because 0 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.

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

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.

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

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

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

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. x 1 sx x 2 y x 1 x Wind will pile up water in the direction toward which it blows. x 2

Slopes produced by different winds in Chesapeake Bay

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:

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

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

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

Tides in Panama City

(JGR, 1982, 87(C 10), 7985)

Thomson et al. (2007, JGR, 112, C 09022)

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

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

(JGR, 1982, 87(C 10), 7985)

C N N C

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