Discussion: a critique of “Modeling suspended sediment distribution in continental shelf upwelling/downwelling settings”

Abstract

A recent one-dimensional numerical model, the so-called GJ model, neglected horizontal advection and diffusion terms and used vague physical definition for its boundary conditions. An alternative two-dimensional numerical model, which corrects the GJ model’s deficiencies, is proposed to evaluate the physical effects of upwelling/downwelling on suspended sediment concentration (SSC) on continental shelves. The general SSC patterns derived from the two models are similar. However, in the case where settling velocity is larger than the maximum upwelling/downwelling velocity, the GJ model shows a homogeneous distribution of SSC, whereas the two-dimensional model identifies a distinct maximum SSC in the middle of the water column in combined upwelling and downwelling systems, and a SSC gradient in upwelling settings. Furthermore, when the maximum upwelling velocity is larger than the settling velocity, the GJ model shows a maximum SSC at the water surface, whereas the SSC is lower at the water surface when using the two-dimensional model.