Evidence for PDO-controlled shoreline change along the Cooloola Sand Mass, Queensland, Australia
Josh Kelly
PhD Candidate, SDSU
Committee Chair: Dr. Allen Gontz
Wednesday, November 28th at 1pm
CSL 422
Abstract
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), Pacific Decadal Oscillation (PDO) and the Subtropical Ridge Latitude (STR-L) and Pressure (STR-P) on shoreline dynamics along the Cooloola Sand Mass, Queensland are assessed by performing correlation statistics between their respective index values and shoreline change distances calculated by the Digital Shoreline Analysis System. PDO shows a significant positive correlation with shoreline change (r = 0.27, p-value = 0.003), indicating that the open coast shorelines of Cooloola progrades (retreats) during positive (negative) PDO phases. There was no observed correlation between changes in shoreline position and SAM, STR-P, and STR-L variability and weak correlation with SOI. An increase in cyclone and anticyclone intensity and pressure in the Tasman Sea during PDO- is suggested to be the climate mechanism causing this shoreline response to PDO phase changes. The clear correlation of negative PDO phases with coastal erosion shown in this study provides significant insight into how the shoreline will respond to future predicted PDO changes.