Shallow sea dynamics from CZCS imagery

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Shallow sea dynamics from CZCS imagery

Boxall, S.R. / Robinson, I.S.

Abstract Reliable techniques for the accurate atmospheric correction and calibration of CZCS data in optical case 2 waters have not yet been achieved. Nonetheless the spatial variation of colour signature in the CZCS imagery of the U.K. shelf seas contains oceanographically useful information. Using two case studies, this paper explores ways in which ocean colour data can yield insights into the dynamical processes controlling shallow seas, and can provide quantitative measures of dispersion, mixing and circulation despite the lack of accurate atmospheric corrections. In each case the patterns of colour distribution in images of the English Channel have been interpreted in terms of the spatial distribution of colour-controlling tracers, i.e. suspended sediment and chlorophyll pigments. For the first case a numerical advective diffusive model of the region has been run to predict the dispersion of tracers from different sources under a variety of imposed residual flow and tidal diffusion conditions. Comparison between the patterns of tracer in the imagery and those predicted by the model enable conclusions to be drawn about the nature of the dispersive processes in the shallow sea, leading to greater confidence in the prediction of pollutant dispersal. In the second study a short series of CZCS images initiated an observational programme into the apparent circulation anomalies in the region. This in turn has led to an extensive study of archived CZCS data which indicates a consistent seasonal pattern for the circulation of parts of the English Channel.