Modelling SPM on the NW European shelf seas

Abstract

AbstractThe Proudman Oceanographic Laboratory Coastal Ocean Modelling System (POLCOMS) has been developed to tackle multidisciplinary studies in coastal/shelf environments. The central core is a sophisticated three-dimensional hydrodynamic model that provides realistic flow fields to interact with, and transport environmental parameters. The model uses realistic forcing with ocean currents and hydrography at the boundary, atmospheric forcing and tides.Suspended particulate matter (SPM) is transported within the water, like any other scalar in the model; it is advected using a high-order scheme and mixed vertically using diffusion coefficients from a second moment turbulence closure. In addition, the SPM transport is influenced by a number of processes unique to this problem, such as: the transfer between the lowest level of the model and the bed layer in which the resuspension and deposition takes place is dependent on the erosion rate, the particle settling velocity and the critical stresses for erosion and deposition. The particular application described in this paper is an annual simulation for the NW European shelf for a single sediment class.The simulation shows the expected seasonal variation in spatial patterns and a clear tidal signal in the SPM resuspension. Also evident is a fortnightly/monthly variability due to the spring-neaps and the M2-N2 cycles. There are also quarter-diurnal and semi-diurnal cycles in SPM, due to tidal resuspension and advection respectively. The above tidal suspension behaviour, as well as, the net transport direction are in agreement with historical observations of SPM.