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African Journal of Marine Science

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Extreme significant wave height climate in the Gulf of Guinea

AA Osinowo, EC Okogbue, EO Eresanya, OS Akande

Abstract


This article investigates spatio-temporal trends for different return periods of extreme significant wave height (SWH) in the Gulf of Guinea (GG),  northeastern tropical Atlantic Ocean, based on a 37-year (1980–2016) wave
hindcast. High-resolution reanalysis windfield datasets were used to force the spectral wave model WAVEWATCH III. The wave hindcast information was validated using data gathered from the US National Data Buoy Center. The model performance was adequate. In a spatial analysis, the trends were less than 0.3 m decade−1 in all parts of the GG, and were increasingly positive westwards, extending to the far western part of the GG; trends below 0.01 m decade−1 dominated in the eastern part and some areas of the northern part of the gulf. Temporal analysis showed that the trends were negative in all cases. Spatio-temporal trends in the return periods for the 99th-percentile wave height were generally weak. Also, trends in the yearly, seasonal and monthly means of extreme SWH all generally increased from east to west in the GG. Furthermore, temporal trend analysis showed that extreme SWH exhibited an increasing trend of 0.0041 m y–1 throughout the 37-year period; by season, it exhibited a declining trend of −0.0005 m y–1 in winter, and an increasing trend of 0.0048 m y−1 in summer. The observed increasing positive trend of extreme SWH westward in the GG, however, suggests an increasing storminess towards the western part of the gulf, with potential implications for coastal flooding and erosion, and consequences for coastal structures.


Keywords: buoy data, extreme wave height, mid-Atlantic Ocean, regional model, return periods, spatio-temporal trends, wave climate, wave  hindcasts




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