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Spatial and temporal variability and long-term trends in skew surges globally

Spatial and temporal variability and long-term trends in skew surges globally
Spatial and temporal variability and long-term trends in skew surges globally
Storm surges and the resulting extreme high sea levels are among the most dangerous natural disasters and are responsible for widespread social, economic and environmental consequences. Using a set of 220 tide gauges, this paper investigates the temporal variations in storm surges around the world and the spatial coherence of its variability. We compare results derived from two parameters used to represent storm surge: skew surge and the more traditional, non-tidal residual. We determine the extent of tide-surge interaction, at each study site, and find statistically significant (95% confidence) levels of tide-surge interaction at 59% of sites based on tidal level and 81% of sites based on tidal-phase. The tide-surge interaction was strongest in regions of shallow bathymetry such as the North Sea, north Australia and the Malay Peninsula. At most sites the trends in the skew surge time series were similar to those of non-tidal residuals, but where there were large differences in trends, the sites tended to have a large tidal range. Only 13% of sites had a statistically significant trend in skew surge, and of these approximately equal numbers were positive and negative. However, for trends in the non-tidal residual there were significantly more negative trends. We identified 8 regions where there were strong positive correlations in skew surge variability between sites, which meant that a regional index could be created to represent these groups of sites. Despite strong correlations between some regional skew surge indices, none were significant at the 95% level, however, at the 80% level there was significant positive correlation between the north-west Atlantic—south and the North Sea. Correlations between the regional skew surge indices and climate indices only became significant at the 80% level, where Ni?o 4 was positively correlated with the Gulf of Mexico skew surge index and negatively correlated with the east Australia skew surge index. The inclusion of autocorrelation in the calculation of correlation greatly reduced their significance, especially in the short time-series used for the regional skew surge indices. Skew surge improved the representation of storm surge magnitudes, and therefore allows a more accurate detection of changes on secular and inter-annual time scales.
storm surge, extreme sea level, Tide-surge interaction, regional climate, Skew surge
29
Mawdsley, Robert J.
29990d1f-dfd8-4d68-b21a-089f2d03a3ed
Haigh, Ivan D.
945ff20a-589c-47b7-b06f-61804367eb2d
Mawdsley, Robert J.
29990d1f-dfd8-4d68-b21a-089f2d03a3ed
Haigh, Ivan D.
945ff20a-589c-47b7-b06f-61804367eb2d

Mawdsley, Robert J. and Haigh, Ivan D. (2016) Spatial and temporal variability and long-term trends in skew surges globally. Frontiers in Marine Science, 3, 29. (doi:10.3389/fmars.2016.00029).

Record type: Article

Abstract

Storm surges and the resulting extreme high sea levels are among the most dangerous natural disasters and are responsible for widespread social, economic and environmental consequences. Using a set of 220 tide gauges, this paper investigates the temporal variations in storm surges around the world and the spatial coherence of its variability. We compare results derived from two parameters used to represent storm surge: skew surge and the more traditional, non-tidal residual. We determine the extent of tide-surge interaction, at each study site, and find statistically significant (95% confidence) levels of tide-surge interaction at 59% of sites based on tidal level and 81% of sites based on tidal-phase. The tide-surge interaction was strongest in regions of shallow bathymetry such as the North Sea, north Australia and the Malay Peninsula. At most sites the trends in the skew surge time series were similar to those of non-tidal residuals, but where there were large differences in trends, the sites tended to have a large tidal range. Only 13% of sites had a statistically significant trend in skew surge, and of these approximately equal numbers were positive and negative. However, for trends in the non-tidal residual there were significantly more negative trends. We identified 8 regions where there were strong positive correlations in skew surge variability between sites, which meant that a regional index could be created to represent these groups of sites. Despite strong correlations between some regional skew surge indices, none were significant at the 95% level, however, at the 80% level there was significant positive correlation between the north-west Atlantic—south and the North Sea. Correlations between the regional skew surge indices and climate indices only became significant at the 80% level, where Ni?o 4 was positively correlated with the Gulf of Mexico skew surge index and negatively correlated with the east Australia skew surge index. The inclusion of autocorrelation in the calculation of correlation greatly reduced their significance, especially in the short time-series used for the regional skew surge indices. Skew surge improved the representation of storm surge magnitudes, and therefore allows a more accurate detection of changes on secular and inter-annual time scales.

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More information

Accepted/In Press date: 29 February 2016
Published date: 21 March 2016
Keywords: storm surge, extreme sea level, Tide-surge interaction, regional climate, Skew surge
Organisations: Physical Oceanography, Faculty of Engineering and the Environment

Identifiers

Local EPrints ID: 397342
URI: http://eprints.soton.ac.uk/id/eprint/397342
PURE UUID: 8f4e6789-e33c-429b-84fd-87b06ff0d0ad

Catalogue record

Date deposited: 13 Jul 2016 08:36
Last modified: 16 Dec 2019 19:51

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