Oral D1 Cross-Sector Applications & Solutions

5:15 PM - 5:30 PM JST(8:15 AM - 8:30 AM UTC)

[BSG7SMHd-06] Impact of Coastal Upwelling on Biological Production: Numerical Modeling Investigation of the Situation on the Ghanaian Shelf

*Kwabena Danso¹ (1.     Africa Centre of Excellence in Coastal Resilience, University of Cape Coast (Ghana))

In Ghana and other countries around the Gulf of Guinea, the strength of upwelling is mostly assessed based on changes in sea surface temperature (SST). This approach ignores surface wind conditions that drive Ekman transport and the upwelling of nutrient-rich water, which stimulate biological production. Therefore, the purpose of this study was to evaluate a new index for assessing upwelling events on the coast of Ghana. The study utilised satellites measurements (wind, nitrate, etc.) from the Copernicus Marine Service from 1995 to 2021. The occurrence of upwelling was assessed using the Coastal Upwelling Transport Index (CUTI) based on the combined effect of alongshore wind and geostrophic velocities. Nutrient input associated with upwelling was assumed to be directly related to Biologically Effective Upwelling Transport Index (BEUTI); vertical transport of nitrate by upwelling into productivity euphotic zones of the ocean. A generalised addictive model was applied to investigate relationship between the strength of upwelling and abundance of three small pelagics (Sardinella maderensis, S. aurita, and Engraulis encrasicolus). Intense upwelling was predicted to occur in July, August and September of each year, with moderate to significant relationship between average CUTI (1.94 ± 0.37 m2 s-1) and the concentration of nutrients such as silicate (R2 = 0.70, p = 0.001), phosphate (R2 = 0.54, p = 0.007) and nitrate (R2 = 0.42, p = 0.022) in surface waters of the ocean. Consequently, nutrient input was also significantly high in July, August and September with BEUTI at 7.16 ± 3.45 STD mmol m-1 s-1 and had a strong relationship between abundance of S. maderensis (R2 = 0.193, p = 0.0279) and E. encrasicolus (R2 = 0.194, p = 0.0279). These results agree with previous reports on the characteristics of coastal upwelling in Ghana.