DEVELOPMENT OF A MODEL TO REPRODUCE OBSERVED SUSPENDED SEDIMENT DISTRIBUTIONS IN THE SOUTHERN NORTH-SEA USING PRINCIPAL COMPONENT ANALYSIS AND MULTIPLE LINEAR-REGRESSION

As part of the NERC North Sea Project (1987-1992), concentrations of f ine suspended particulate matter were determined at over 100 locations on 15 monthly survey cruises. Each of these monthly data sets were in terpolated to provide continuous ''synoptic'' representations over the southern North Sea (south of 56 degrees N). Here, statistical techniq ues are used in conjunction with numerical model simulations to interp ret these data. Principal Component Analysis is performed on these mon thly series of observations to locate statistically significant source s and sinks of suspended particulate matter. This analysis reveals the month-to-month variability of a primary source, accounting for around 80% of the total variation in the observations, and located in the vi cinity of The Wash estuary and adjacent coast. A numerical dispersion model is then developed to simulate the erosion, settling and transpor t of fine suspended sediment from this source. The formulations and as sociated coefficients used to describe re-erosion and settling rates a re then fine-tuned by comparison with observations. In the second part of this study, the sediment model developed is used to simulate dispe rsion from discrete sources. Thence a Multiple Linear Regression techn ique, as described by McManus and Prandle (1994) (in Marine Pollution Bulletin 28, 451-455), is used to fit these modelled dispersion patter ns to the original observations to determine rates of sediment supply from these discrete sources. This technique reveals that (i) riverine sources are not statistically significant and (ii) the East Anglian so urces are small in magnitude compared with the Dover Strait and northe rn North Sea sources. Further analysis explains this apparent contradi ction with the first part of the study by illustrating how the longer effective flushing times of the two coastal sources amplifies their ne t contribution to the suspended particulate matter distribution in the southern North Sea. Estimates of mean annual supply from the statisti cally significant sources (in 10(6) t) are Dover Strait, 44.4, norther n North Sea, 41.7, The Wash, 3.2, and Suffolk Coast, 0.7. Comparable e stimates published in the 1993 North Sea Quality Statics Report (North Sea Task Force, Olsen and Olsen, Denmark) are generally in reasonable agreement. Likewise, both the location and rates of supply from the s ources determined in this study are in broad agreement with the earlie r estimates of McCave (1987) (in Journal of the Geological Society 144 , 149-152). Thus, the success achieved provides encouragement towards the goal of developing robust suspended sediment models of shelf seas. (C) 1997 Elsevier Science Ltd.