Comparison and characteristics of oceanographic in situ measurements and simulations above submerged sand waves in a tidal inlet

Hennings, Ingo and Herbers, Dagmar (2016) Comparison and characteristics of oceanographic in situ measurements and simulations above submerged sand waves in a tidal inlet [Talk] In: HYDRO 2016, 08.-10.11.2016, Rostock-Warnemünde, Germany.

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Ocean color and its transparency are related to turbidity caused by substances in water like
organic and inorganic material. One of the essential climate variables (ECV) is ocean color.
However, this implies the correct interpretation of observed water quality parameters.
Acoustic Doppler Current Profiler (ADCP) data of the three-dimensional current-field, echo
intensity, modulation of suspended sediment concentration (SSC), and related water levels
and wind velocities have been analyzed as a function of water depth above submerged
asymmetric compound sand waves during a tidal cycle in the Lister Tief of the German Bight
in the North Sea. Signatures of vertical current component, echo intensities and calculated
SSC modulations in the water column depend strongly on wind and current velocity. Bursts of
vertical current component and echo intensity are triggered by sand waves itself as well as by
superimposed megaripples due to current wave interaction at high current  1.0 m s-1 and
wind speeds  10.0 m s-1, preferably of opposite directions, measured at high spatial
resolution. The magnitude of currents and SSC modulations during ebb and flood tidal current
phases are only weakly time dependent, whereas the local magnitudes of these parameters are
variable in space above the sand waves. Intense ejections caused by tidal current velocity
transport higher SSC near the bottom boundary layer at the sand waves superimposed by
megaripples towards the free water surface. Such typical upwelling mechanism above sand
waves creates distinct SSC signatures of remote sensing data visible in air- and space-borne
optical imagery. Hydrodynamic parameters such as dynamic buoyancy density, total energy
density and action density due to semi-diurnal M2 tide motion which are associated with sand
waves are investigated and analyzed. Results and characteristics of simulated hydrodynamic
parameters in coastal waters above sand waves are presented. It is shown that ADCP
measurements are to be consistent with simulations based on the applied theory.

Document Type: Conference or Workshop Item (Talk)
Keywords: Acoustic Doppler Current Profiler, suspended sediment concentration, asymmetric compound sand wave, dynamic buoyancy density, action density
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Date Deposited: 18 Nov 2016 08:58
Last Modified: 18 Nov 2016 09:04

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