MODELLING EXTREME EVENTS (HURRICANES) AT THE SEAFLOOR IN THE NORTHERN GULF OF MEXICO (Invited Presentation)
Locations and timings of suspended sediment gravity flow were identified by applying energy-based flow-ignition criterea. Wave-induced mass failure and subbottom liquefaction events were also assessed using geotechnical criterea. The downslope persistences, densities and velocities of the turbidity flows yielded by the ignitions were then calculated using high-Reynolds Number adaptations of LES/RANS-TURBINS models (Large-Eddy Simulation / Reynolds Averaged Navier-Stokes). A very important step here was the transfer of these advanced models from laboratory to geographic scales.
As known, much of the shelf sediment mantle is suspended and/or moved during hurricanes, consistent with the modeling results. Many short-lived gravity-flow ignitions occur on the shelf; many at the shelf edge will ignite into fast, erosive and persistent currents. Sediment patchiness and vagaries of hurricane path mean that the pattern of ignitions alters from event to event. A valuable experience in the project was devising workflows and linkages between these advanced, but independent models. The project opens a path to advanced modeling supporting stratigraphic analysis.