- Title
- Spatio-temporal variability of tidal residuals along the New South Wales Coast driven by climate and synoptic processes
- Creator
- Viola, Cristina
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- 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 from 2 to 8 years. However, when investigating climate mode impacts on tidal residuals using the two longest datasets in the record, starting in 1931 and 1969, the significance of the low-frequency IPO in combination with the high-frequency SAM, becomes more apparent (R2 = 0.40), particularly at frequencies ranging from 4 to 16 years. Furthermore, synoptic analyses were conducted to identify CSWs for the 1990 to 2015 period. Generation of CSWs is likely associated with a low-pressure system located in the Great Australian Bight, with some events co-occurring with an additional low-pressure system along the coast. The teleconnection of ENSO and SAM during different seasons was also highlighted, as the occurrence of CSWs while SAM was positive was higher during La Niña than during El Niño events, especially during austral winter. This study has provided a new quality-controlled dataset of tidal residuals for NSW that can be used in subsequent studies. In addition, the role of large-scale climate modes in driving extreme tidal residuals that may cause inundation along the NSW coast was highlighted. Hence, the findings presented herein will also assist in updating existing management plans for the NSW coast and adjacent areas to account for long-term forecasting of extreme water levels and associated inundation caused by Pacific and Southern Ocean large-scale modes. Finally, the study has also improved knowledge of the frequency and characteristics of CSW as well as their causal mechanisms, which are known to result in flooding of coasts and estuaries in NSW during the passage of CSW. Based on the results, management can be improved with information to monitor the occurrence and the number of days to expect for a CSW to reach different locations along the NSW coast. Overall, the results of this study will assist in decision making and preparing long-term solutions for flood risk, especially as climate modes contribute to increased MSL, and projections indicate that sea levels will continue to rise.
- Subject
- spatio-temporal variability; tidal; New South Wales Coast; climate change
- Identifier
- http://hdl.handle.net/1959.13/1493837
- Identifier
- uon:53652
- Rights
- Copyright 2022 Cristina Viola
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
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| View Details Download | ATTACHMENT01 | Thesis | 63 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 3 MB | Adobe Acrobat PDF | View Details Download |