A Numerical Study of Tropical Cyclone‐Induced Sediment Dynamics on the Australian North West Shelf

Abstract

AbstractOwing to their strong forcing of the ocean surface, tropical cyclones strongly modify the hydrodynamics of Australia's North West Shelf (one of the world's tropical cyclone hot spots), which in turn plays a dominant role in its sediment dynamics. Previous modeling studies have focused on describing the short‐term sediment dynamics during individual tropical cyclones but have lacked validation of the responses using field observations. As a consequence, the long‐term cumulative impact of the tropical cyclones on the residual sediment transport pathways at the shelf scale remains unclear. In this study we apply a sediment transport model over the North West Shelf, validate its performance using an extensive field data set, and implement a 14‐year‐long model simulation to assess the sediment fluxes. The model results confirm the overwhelming role tropical cyclones play on sediment transport processes over most of the shelf, despite each cyclone only influencing a small portion of the shelf at a particular time. Overall, we identified 19 tropical cyclone events over the 14‐year period, which, despite accounting for less than 5% of time, were found to drive the majority of both the suspended sediment alongshore and seaward cross‐shore transport. The results revealed significant interannual variability of the tropical cyclone‐induced sediment dynamics with greater suspended transport during the three consecutive Ningaloo Niño years (2011–2013) where sea surface temperatures off northwestern Australia were anomalously warm with elevated tropical cyclone activity.