Abstract for the 18th Physics of Estuaries and Coastal Seas Conference, 2016
b
a
Figure 1: Study Site. Panel (a) shows a map of the study site in the tidal inlet, between the islands of Langeoog in the West and Spiekeroog in the East, in the German Wadden Sea. The colored contours display the average water depth. S marks the position of the permanently anchored vessel, R/V Ludwig Prandtl, and G the position of the gauge. A cross-section of the channel along the y-axis is displayed in the small panel to the right (b).
Estuarine Circulation vs Tidal Pumping: Sediment Transport in a Well-Mixed Tidal Inlet
Johannes Becherer
1
G¨otz Fl¨oser
2
Lars Umlauf
3
and
Hans Burchard
4
Keywords: sediment transport, tidal pumping, estuarine circulation, tidal inlets. Abstract High-resolution water column observations have been carried out in the Wadden Sea to understand SPM transport in well-mixed tidal channels. These observations include more than 4000 consecutive CTD-, microstructure shear and turbidity profiles from a free-falling micro-structure profiler, as well as velocity data from an ADCP and SPM samples for calibration. A horizontal density gradient was established by a landward temperature gradient built up during an extraordinarily warm and calm spring season. Although earlier studies (Becherer et al., 2011, 2015) pointed towards the existence of a residual vertical exchange flow, here we present the first direct observations of along-channel estuarine circulation in the Wadden Sea (Fig. 2). Primarily driven by tidal asymmetries (Burchard et al., 2011; Becherer et al., 2015), estuarine circulation in the Wadden Sea can be substantially altered by wind forcing (Purkiani et al., accepted). During the second part of our campaign a strong up-estuary directed wind weakened and eventually even reversed estuarine circulation and yielded a net barotropic eastward transport (Fig. 2). SPM concentrations showed a strong quarter-diurnal signal with maxima near full flood and full ebb and were generally lower during the calm period and increased during the windy period, mainly due to wave-related resuspension over nearby inter-tidal flats. 1 College of Earth, Ocean, and Atmospheric Sciences (CEOAS), Oregon State University, BURT Hall II, Corvallis, OR 97330, USA. (
[email protected]) 2 Helmholtz-Zentrum Geesthacht (HZG), Geesthacht, Germany. (
[email protected]) 3 Leibniz-Institute for Baltic Sea Research (IOW), Seestraße 15, D-18119 Warnem¨ unde, Germany (
[email protected]) 4 Leibniz-Institute for Baltic Sea Research (IOW), Seestraße 15, D-18119 Warnem¨ unde, Germany (
[email protected])
Abstract for the 18th Physics of Estuaries and Coastal Seas Conference, 2016
Pc u
0
-10
a
-5
0.05 =
0
hz
