Predicting seabed change as a function of climate change over the next 50 yr in the Australian southeast

The Australian seabed is influenced by extreme weather conditions of various types, including cyclones, high tidal ranges, offshore currents, and storm waves. Over the past two centuries, substantial progress in our understanding of the seabed and environmental conditions has been made by studies of seabed sedimentology, hydrodynamics, and habitat mapping. As part of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) "Wealth from Oceans" flagship program, we have been involved in a five year study to investigate and predict the effect of possible climate change scenarios on the seabed over the next 50 yr. As an initial phase of this project we have taken the southeast region of the Australian seabed as our study area. The seabed responses to current climate and possible future climatic conditions over the next 50 yr have been simulated for the first time by a state-of-the-art numerical model, Sedsim. We found: (1) that the contribution of river-carried sediment (redistributed by marine processes) to the region's seabed, even with the wettest predicted climate change, is limited. In general, the fluvial sediment in the southeast region cannot keep pace with the action of strong marine forces, such as waves and currents. Therefore, most of the seabed suffers from erosion due to lack of sediment to distribute. This situation would get worse if the local climate swings toward the high-energy side. (2) The generally high wave energy, significant tidal currents, and frequent surges of wind-driven currents make the local seabed highly mobile and sensitive to hydrodynamic change. (3) The change of turbidite activity among different climate scenarios is insignificant with regard to the number of submarine slope failures, the areas affected, and the seabed median grain size.