Browsing by Author "Foli, B.A.K."
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Item Assessment of past and future potential of ocean wave power in the Gulf of Guinea(INTERNATIONAL JOURNAL OF SUSTAINABLE ENGINEERING, 2023) Dahunsi, A.M.; Foli, B.A.K.the aim of identifying high-density wave energy locations for potential exploitation. To estimate wave power density (WPD) for three time periods (past: 1979–2005, mid-century: 2026–2050, and end-century: 2081–2100), we utilized significant wave height and mean wave period obtained from eight General Circulation Models. Using an ensemble of these WAVEWATCH III simulated datasets, we calculated WPD and assessed overall and seasonal trends, projecting changes under Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios. Results revealed higher potential WPD in the western GoG, particularly near the coast, with increased values offshore. Spatially, WPD change rates varied widely (−0.021 to 0.039 kW/m per year), suggesting both positive and negative trends, though generally low. Projections indicated a potential increase from 0.5 to 1.0 kW/m by the end of the century. The estimated potential power for harvesting exceeded 14,000 MW, with offshore regions showing better wave con verter performance. This study concludes that GoG's wave energy is a promising renewable resource, offering a potential solution to future power needs and contributing to regional greenhouse gas emission mitigation.Item Investigation of Selected Trace and Heavy Metals in Two Tropical Fish Species from the Coastal Waters of Ghana(International Journal of Science and Technology 3: 40-47, 2013) Nyarko, E.; Foli, B.A.K.; Achel, D.G.; Botwe, B.O.; Adom, T.; Fianko, J.R.; Osae, S.D.Cadmium (Cd), copper, (Cu), Iron (Fe), lead (Pb), and zinc (Zn) burdens were determined by atomic absorption spectrophotometry (AAS) in two tropical fish species (Chloroscombrus chrysurus and Sardinella maderensis) from the western coast of Ghana. Fish samples were collected during three designated Sampling Periods (January 2008 to March 2008 - Periods 1; September 2008 to November 2008 - Period 2; and February 2009 to March 2009 - Period 3) at three sites (Half-Assini, Aboadze and Elmina). Trace elements and heavy metal concentrations in both species followed the order Fe>Zn>Cu while Cd and Pb were below detection limits. High levels of Fe were detected in the fish samples with concentration ranges of 13.05-376.4 μg/g dw. Levels of Cu generally recorded during Period 1 were above FAO maximum recommended limits of 30 μg/g in fish while Zn burdens were below FAO recommended limit of 40 μg/g. S. maderensis and C. chrysurus, can be considered safe for human consumption with respect to Cd, Pb and Zn contaminations. However, Cu will require further monitoring to protect public health. Hazard quotients and hazard indices computed indicate that metal exposure from consumption of the two fish species will not result in any appreciable health risk. Levels of Cu and Zn recorded may however pose threats to physiological functioning of fish since levels were high enough to cause sublethal effects to fish. Metal burdens studied provide background information prior to the commercial exploitation of oil in Ghana’s marine waters.Item Seasonal Variability of Sea Surface Salinity in the NW Gulf of Guinea from SMAP Satellite(Remote Sensing in Earth Systems Sciences, 2022) Nyadjro, E.S.; Foli, B.A.K.; Agyekum, K.A.; et al.The advent of satellite-derived sea surface salinity (SSS) measurements has boosted scientific study in less-sampled ocean regions such as the northwestern Gulf of Guinea (NWGoG). In this study, we examine the seasonal variability of SSS in the NWGoG from the Soil Moisture Active Passive (SMAP) satellite and show that it is well-suited for such regional studies as it is able to reproduce the observed SSS features in the study region. SMAP SSS bias, relative to in-situ data comparisons reflects the differences between skin layer measurements and bulk-surface measurements that have been reported by previous studies. The study results reveal three broad anomalous SSS features: a basin-wide salinification during boreal summer, a basin-wide freshening during winter and a meridionally-oriented frontal system during other seasons. A salt budget estimation suggests that seasonal SSS variability is dominated by changes in freshwater flux, zonal circulation and upwelling. Freshwater flux, primarily driven by the seasonally varying Intertropical Convergence Zone is a dominant contributor to salt budget in all seasons except during fall. Regionally, SSS is most variable off southwestern Nigeria and controlled primarily by westward extensions of the Niger River. Anomalous salty SSS off the coasts of Cote d’Ivoire and Ghana, especially during the summer, is driven mainly by coastal upwelling and horizontal advection.Item A WAVEWATCH III® model approach to investigating ocean wave source terms for West Africa: Non-linear wave-wave interaction source terms(Applied Ocean Research, 2022) Foli, B.A.K.; Ansong, J.K.; Addo, K.A.; Wiafe, G.Ocean wave forecasting for West Africa has mostly relied on global parameterization schemes and data outputs. Investigating non-linear ocean wave-wave interaction source terms (Snl) for the region that forms part of the wave model parameterization schemes, is a contribution of this study towards developing a regional wave modelling scheme for West Africa. The study evaluates five non-linear source-term configurations with the WAVEWATCH III® (WW3) numerical ocean wave model version 5.16; (i) No source term applied (NL0); (ii) Discrete Interaction Approximation (DIA): NL1, (iii) Exact Interaction Approximation: NL2, (iv) Generalized Multiple DIA (NL3) and (v) Two-Scale Approximation (NL4) in order to determine best-performing Snl for projecting significant wave heights and directions for the region. The wave simulations were run on three separate grids comprising a low-resolution West Africa grid (latitudes 10° S–30° N; longitudes 35° W–15° E), high-resolution south-eastern (latitudes 2o S – 8o N; longitudes 10o W – 10o E) and north-western (latitudes 10o N) – 25o N; longitudes 30o W – 10o W) sub-grids. Simulations for the entire West Africa grid produced higher accuracy for the wave parameters compared to the higher-resolution sub-grids. NL0 best estimates are significant wave height, whereas NL3 best estimates wave directions for the West Africa grid. For combined stations of the south-eastern sub-grid, while NL1 best estimates wave heights, NL3 best estimates the wave directions with possible alternation with NL1 due to insignificant differences. Similarly, for the north-western sub-grid, while NL1 best estimates significant wave heights; NL0 best estimates wave directions with similar ability to alternate with NL2 in projecting wave directions. Generally, insignificant differences exist between the source terms in projecting wave directions, especially for the north-western sub-region, implying that any of the source terms may be used in projecting wave directions without significantly compromising on accuracy. Thus, NL1, which best estimates significant wave heights for both the south-eastern and north-western sub-regions can also be used in estimating the wave directions. Similarly, NL0 would be appropriate for the entire West African region