Coastal Response to Latitudinal Shifts in Wave Climate in Southeast Australia using a Surrogate Buoy Approach

Most Global Climate Models (GCM) agree that an expansion of the tropics will continue with greenhouse warming, although the magnitude of this expansion is largely under-estimated. A first-order impact is wave climate and coastal response in the sub-tropics. We use a latitudinal array of mid-shelf wave buoy observations along the Southeast Australian Shelf (SEAS) to forecast wave climate change with tropical expansion. We suggest that the present-day modal wave climate from more equatorward SEAS buoys can be used as surrogate data to project future wave climate change at more poleward locations. This approach allows multiple scenarios of the magnitude of future tropical expansion to be examined, based on the latitudinal separation between buoys. We use the modal wave climate typology of Mortlock and Goodwin (2015) to relate wave climate change to synoptic climate. We then use a coupled spectral wave and morphodynamic model to evaluate wave climate change scenarios for an idealised headland-bay beach setting. The method provides an alternative to the downscaling approach for wave climate forecasting, which inherits and adds to the uncertainty of the GCM projections. Our results are relevant for other Southern Hemisphere east coasts in South America and Africa, and Northern Hemisphere west coasts in North America and Europe with similar mid-shelf wave climate and sediment transport regimes in the sub-tropics.