THE IMPACT OF CLIMATE CHANGE ON SHORELINE DYNAMICS ALONG SOUTHEAST QUEENSLAND, AUSTRALIA

Wave climate oscillations in southeast Queensland have been well correlated to changes in the Southern Oscillation Index (SOI), but observations and understanding of shoreline change associated with the variable wave climate have been limited due to a paucity of aerial photography, LiDAR, and other beach profiling datasets in this region. A multi-decadal, sub-annual temporal resolution shoreline dataset spanning 1996 to 2017 was produced using satellite imagery collected by Landsat 5, 7, and 8. A total of 147 shoreline positions were delineated using the Modified Normalized Difference Water Index on cloud-free imagery and corrected for horizontal offsets forced by variable tide stages at the satellite flyover time. The relative influence of SOI, the Southern Annular Mode (SAM), and the Subtropical Ridge Latitude (STR-L) and Pressure (STR-P) on shoreline dynamics along Rainbow Beach, Queensland are assessed by performing correlation statistics between their respective index values and shoreline change distances calculated by the Digital Shoreline Analysis System. Both SOI and SAM show a negative correlation with shoreline change (SOI: r = -0.1398, p-value = 0.09; SAM: r = -0.1893, p-value = 0.02), indicating that the Rainbow Beach shoreline retreats (progrades) during both positive (negative) SOI and SAM phases. There was no observed correlation between changes in shoreline position and STR-P and STR-L variability. Observations of major shoreline erosion events show that the majority occur during or just after the austral winter months when positive SAM phases are most associated with an enhanced erosive wave climate. These results suggest that SAM has a likely influence on wave climate and shoreline change in southeast Queensland. In addition, the clear correlation of positive SAM and SOI phases with coastal erosion shown in this study provides significant insight into how the shoreline will respond to predicted more frequent La Niña and positive SAM conditions over the next century due to elevated global mean temperatures.