Modelling and Assessing the Trends in Wave Climate Over The Past Four Decades in the Coast of Gulf of Guinea

Abstract

ABSTRACT The focus of this study is the assessment of the past wave conditions in the Gulf of bGuinea region of the West African coast to get a better understanding of the trends the waves have been following over the past four decades. The third-generation spectral wave model, WAVEWATCH III (WW3), was used to hindcast the wave climate between 1st January, 1980 – 31st December, 2019, which provided data on significant wave height (Hs), mean wave period (Tm), mean wave direction and mean wind speed (U10). Validation results confirmed that WW3 is an efficient model for simulating wave condition as it agrees well with observation and other datasets like ERA5 (European Centre for Medium-Range Weather Forecasts - ECMWF Reanalysis 5th Generation). The trend analyses done showed that the Hs with average values of 1.0836 m, 0.9312 m and 1.1913 m on annual, winter and summer bases increased at rates of 2.6 x 10-3 m, 1.6 x 10-3 m and 3.4 x 10-3 m per year, respectively. For Tm, average values of 5.3897 s, 5.3876 s and 5.3911 s for annual, winter and summer changed at rates of 6.1353 x 10-4 s, -1.7 x 10-3 s and 2.3 x 10-3 s per year, respectively. Mean values of 4.7001 m/s. 4.2344 m/s and 5.0292 m/s were estimated for U10 on annual, winter and summer bases increasing at rates of 3.5 x 10-3 m/s, 4.2 x 10-3 m/s and 3.1 x 10-3 m/s per year, respectively. The wave direction is also observed to be predominantly S-SW mostly originating from the southwestern Atlantic Ocean. The statistical projections done for various return period showed that this increase will continue into the future with higher risks to coastal and offshore structures by the end of the century in 2100.