Hans Burchard
Leibniz Institute for Baltic Sea Research Warnemünde
Coastal Ocean Dynamics
Seventh course: Estuarine Dynamics
The principle of estuarine circulation
MacCready and Geyer (2010)
Knudsen formula of 1900
s=0Volume conservation:
Salt conservation: 0
Analytical solution for estuarine circulationBalance between pressure gradient and friction:
.
With
we obtain the analytical solution:
.
Example solution
Tidal straining
after flood
after ebb
MacCready and Geyer (2010) after Simpson et al. (1990)
MacCready & Geyer (2010) after Jay & Musiak (1994)
Estuarine circulation due to tidal straining
75% level
75% level
Result:Tidal straining makes about 2/3 of estuarine circulation.
With full-scale 1Dmodel (GOTM, www.gotm.net):Gravitational circulation and tidal straining profilescan be decomposed.
Burchard and Hetland (JPO 2010)
Estuarine circ.Straining
Gravitational
Simple model simulations of estuarine circulation
under tidally energetic conditions
MacCready & Geyer (2010)
Lateral circulation in tidal estuaries
Flood currents are faster in the deep channel such that salinity becomes higher in the channel centre than at the sides. This lateral density gradient then causes lateral circulation. Ebb is
vice versa.
Nunes & Simpson (1985)
Floating material collected at tidal front during flood
(Conwy River, Wales, UK)
MacCready & Geyer (2010)
Estuarine circulation due to lateral circulation
During flood high (positive) surface momentum is vertically transported to the near bed region. During ebb, relatively high
(negative, but less negative than in channel centre) is transported from the sides to the central near-bed region. This
both supports estuarine circulation.
Enhancement of estuarine circulation in channelised tidal flow
(2D slice modelling with GETM)
Burchard et al. (JPO 2011)
www.getm
.eu
Circulation in transverse estuary
Transverse structure of estuarine circulation
Burchard et al. (JPO 2011)
Tidal straining circulation Gravitational circulation
Advective circulation Barotropic circulation
Estuarinecirculationdrives SPMfluxes
Estuarine circulation drives SPM fluxes
Observations in the Elbe estuary:
Kappenberg et al. (1995)
Generation of estuarine turbidity maxima (ETMs)
Sediment accumulation
Consequences of estuarine circulationon sediment transport
ETM
ETM = estuarine turbidity maximum
Jay and Musiak (1994)
Modelling (2DV) ETM formation
Burchard and Baumert (1998)
The lower Elbe River
Observations of ETM in lower Elbe River
Salinity (g/kg)
Run-off Neu-Darchau = 707 m3/s
Courtesy Jens Kappenberg
Modelling (3D) ETM formation
Burchard et al. (2004)
ebb tide
flood tide
low water
high water
Ems as hyperturbid estuary
Talke et al. (2009)
Is there a positive feedback loop in estuarie?
Winterwerp, 2013
What happened to the Ems estuary?
Pers. Comm. Henk Schuttelaars, 2013
Winterwerp, 2013
Elbe