Modeling Near-Surface Suspended Sediment Concentration in the English Channel

Nicolas Guillou,Francis Gohin,Aurélie Rivier,Georges Chapalain

doi:10.3390/jmse3020193

Abstract

The present study investigates the performances of the three-dimensional multicomponent hydro-sedimentary model ROMS (Regional Ocean Modeling System) to predict near-surface suspended sediment concentrations (SSC) in the English Channel (western Europe). Predictions are assessed against satellite-retrieved observations from raw MODIS and MERIS images for the year 2008 characterized by the highest availability of cloud-free data. Focus is put on improvements obtained with: (1) SSC inputs at the open boundaries; and (2) simple parameterizations of the settling velocity and the critical shear stress. Sensitivity studies confirm the importance of the advection of fine-grained suspended sediments in the central waters of the English Channel exhibiting benefits of refined SSC estimations along the sea boundaries. Improvements obtained with modified formulations of the settling velocity and the critical shear stress finally suggest possible seasonal influences of biological activity and thermal stratification on near-surface SSC.

Highlights

Quantification of suspended sediment concentration (SSC) is very important for several ecological and engineering problems of continental shelf ecosystems
Remote sensing data of near-surface SSC are derived from observed MODIS/AQUA (Moderate Resolution Imaging Spectroradiometer, NASA) and MERIS (Medium Resolution Imaging Spectrometer, ESA) reflectances processed using the semi-analytical algorithm developed by Gohin [1]
An overall good agreement is obtained between numerical results and cartography of spring tidal ranges and currents established by the SHOM (Service Hydrographique et Océanographique de la Marine) [46] in the English Channel

Summary

Introduction

Quantification of suspended sediment concentration (SSC) is very important for several ecological and engineering problems of continental shelf ecosystems. Major concerns include: (1) evaluations of light available for photosynthesis and biological primary production; (2) assessment of water quality in relation to the transport of polluting substances; or (3) investigation of coastal morphological changes induced by human activities. A narrow arm of the North Atlantic ocean tapering eastward to its junction with the North Sea at the Dover Strait, the English Channel (Figure 1) is recognized as a region of strong tidal and wave regimes with intense associated bed erosion and suspended sediment transport, as exhibited in satellite images during winter energetic periods [1] (Figure 2). Lyme Bay. Isle of Wight Solent M3 Alderney Race CHANNEL ISLANDS GULF M2 Guernsey Jersey

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