Highlights ► The first global model for free infragravity (IG) waves is designed and validated. ► DART station measurements in deep water are well explained by the free IG model. ► At 20 km wavelength, spectral IG level above 1 cm 2 /(cycle/km) should occur more than 10% of the time in some regions. ► Such a geophysical error is comparable to the instrument error expected for the future Karin altimeter onboard SWOT.
Ocean infragravity (IG) waves are low-frequency waves generated along shorelines by incident seas and swell and with heights of the order of 1 cm in the open ocean. Despite these small amplitudes, they can be of much importance for ice shelf break up and errors in measurements of sea level by future satellite altimeters. A combination of numerical model results and in situ data is used to show that bottom pressure signals in the infragravity frequency band can be dominated by bursts of energy that travel across ocean basins, and can last for several days. Two particularly strong events recorded in 2008 are studied, one in the North-Pacific and the other in the North-Atlantic. It is shown that infragravity waves can travel across whole oceans basins with the signal recorded on the western shores often dominated by IG waves coming from the opposite shore of that same ocean basin.
Waves are the dominant influence on coastal morphology and ecosystem structure of tropical islands. The geographical positioning of Mauritius near to the Tropic of Capricorn ensures that the eastern regions benefit from the persistent southeast trade winds which influence the incoming surface waves. In this study, we present the high dependence of the wave regimes of windward offshore site on the trade winds. The higher occurrence of incoming waves in the winter season directed in the southeast direction indicates that the trade winds are more prevalent in the winter season. Storms within the extratropical South Atlantic, Indian and Pacific oceans generally propagate towards the east such that extratropical South Atlantic swell energy spreads through the entire Indian Ocean. Since waves are very directional and tend to get shadowed by land masses, Mauritius situated in the line of sight from those sources end up in the shadow region due to the geographical location of Reunion island. In this study, we support the explanation on how the western region of the island gets influenced by episodic swell events. A detailed wave energy resource assessment is provided for different targeted coastal environments around the island. It is revealed that the mean wave power observed in the summer season at one of the sites can attain 28.8 kW/m and is found to be lower as compared to the winter season (31.7 kW/m).
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