Austral swells in La Réunion Island: terrestrial, ocean bottom observations and wave models
Abstract
The Réunion Island in the South-West Indian Ocean is often affected by austral swells, among which extreme events may have strong impacts may have on coastal infrastructures but the very limited oceanography sensors available on and around the island and in the whole SW Indian Ocean impede any direct monitoring of the swell activity. In this study, we analyze successive Austral swells impacting the western coast of La Réunion Island in March-April 2017 by combining terrestrial observations of the swell-induced microseismic noise with in situ wave observations issued from the Ocean Sensor Systems Inc (OSSI) pressure gauges deployed in and off the lagoon and from a Nortek Aquadopp Profiler (AQP) deployed on the reef slope,, together with swell numerical modelling. The reliability of the terrestrial seismic station to characterize the ocean activity in both the primary and secondary microseisms peaks (PM and SM, respectively) for the case of Réunion island is discussed and presented here. By computing the hourly RMS of the PM amplitude, we establish a transfer function linking PM amplitude and wave height, which appears to be valid for any swell height >0.2 m in the Lagoon. The correlation >0.92 between the two parameters suggests that the PM amplitude is a robust proxy for the swell height. From spectral and polarization analyses, the period and direction of the swell are also well retrieved from seismic data. By a continuous monitoring of the SM amplitude, we propose that in case of storm occurring in the southern Indian Ocean it can provide precursory information for any big swell that may hit La Réunion island few days after a SM peak. Combining the SM amplitude with the satellite data, may therefore help estimating the amplitude and arrival time of the swell on the island.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S33B..05R
- Keywords:
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- 0799 General or miscellaneous;
- CRYOSPHERE;
- 9810 New fields (not classifiable under other headings);
- GENERAL OR MISCELLANEOUS;
- 1895 Instruments and techniques: monitoring;
- HYDROLOGY;
- 7299 General or miscellaneous;
- SEISMOLOGY