Spatio-temporal variability of tidal residuals along the New South Wales Coast driven by climate and synoptic processes

• Main Author: Viola, Cristina
• Other Authors: University of Newcastle. College of Engineering, Science & Environment, School of Environmental and Life Sciences
• Format: Thesis
• Language: English
• Published: 2022
• Subjects: spatio-temporal variability; tidal; New South Wales Coast; climate change; Pacific; Southern Ocean
• Online Access: http://hdl.handle.net/1959.13/1493837

Research Doctorate - Doctor of Philosophy (PhD) Coastal water levels often deviate from those predicted by harmonic analysis based purely on astronomical forcing. These variations, termed tidal residuals, can lead to unexpected episodes of extensive and prolonged inundation along the coastal zone and nearby estuaries. This is a problem because of the uncertainty in predicting extreme water levels and the impacts associated with coastal flooding. These impacts include loss of infrastructure within low-lying areas and challenging the effective management of coasts and estuaries. This research aims to understand how Pacific and Southern Ocean large-scale climate modes, including the El Niño Southern Oscillation (ENSO), ENSO Modoki, Interdecadal Pacific Oscillation (IPO) and Southern Annular Mode (SAM), as well as local scale synoptic conditions modulate tidal residuals along the New South Wales (NSW) coast in Australia. To achieve this, a new dataset of tidal residuals for nine high-quality ocean tide gauges located along the NSW coast was compiled. The tidal data were adjusted to the vertical Australian Height Datum (AHD), rainfall-related peaks were removed from the records, gaps infilled, and trends removed. Statistical and spectral analyses were then used to investigate correlations between the tidal residuals and the large-scale climate modes, taking spatial and temporal variability into account. Finally, the tidal residual dataset was used to identify, characterise and assess the drivers of continental shelf waves (CSW) that travel along the NSW coast. CSWs can result in inundation, especially when this occurs during phases of large-scale modes that are favourable to the increased frequency of coastal flooding. The impact of climate modes on tidal residuals varied along the coast, where the collective impact of canonical ENSO and SAM increased southwards. When investigating over the 1987 – 2017 period, these two modes impacted tidal residuals significantly (R2 = 0.45) and covaried at frequencies ranging ...