2019 CSDMS meeting-083
Introducing a wave-supported gravity flow module to Community Sediment Transport Model System
Wave Boundary Layer (WBL) plays an important role in sediment offshore transport and material exchange between seafloor and overlying water, especially during strong wave events when fluid mud (concentration > 10g/L) is formed. We incorporated wave-supported fluid mud (WSFM) processes into the Community Sediment Model System (CSTMS) on the platform of the Coupled Ocean-Atmosphere-Wave-and-Sediment Transport Modeling system (COAWST). A new WBL was introduced between the bottom sigma layer (water) and top sediment bed layer, which accounted for the key sediment exchange processes (e.g., resuspension, vertical settling, diffusion, and horizontal advection) at the water-WBL and WBL-sediment bed boundaries. To test its robustness, we adapted the updated model (CSTMS+WBL) to the Atchafalaya Shelf in the northern Gulf of Mexico and successfully reproduced the sediment dynamics in March 2008, during which active WSFM processes were reported. The CSTMS+WBL model simulated a lutocline between the WBL and overlaid water as well as a stronger onshore/offshore erosion/deposition. Sensitivity tests of free settling, flocculation and hindered settling effects suggested sediments were transported further offshore due to reduced settling velocity in the WBL once fluid mud was formed.