Physical Oceanographic Conditions During Upwelling Season off Ilaro, Ogun State

West African coastal upwelling, driven by the seasonal intensification of equatorward trade winds, dramatically alters sea surface temperatures, nutrient concentrations, and biological productivity in the Gulf of Guinea. This study documents physical oceanographic conditions during the upwelling season off the Ilaro coastal zone in Ogun State, South West Nigeria, contributing observational data to the poorly sampled eastern boundary of the Guinea Current Large Marine Ecosystem. Oceanographic cruises are conducted in June and August 2024 aboard a research vessel, with a conductivity-temperature-depth profiler deployed at 15 stations along three cross-shore transects extending from the two-metre isobath to the 200-metre shelf break. Temperature-salinity diagrams characterise water masses, and the depth of the thermocline is computed as the depth of maximum temperature gradient. Nutrient samples (nitrate, phosphate, silicate) and chlorophyll-a measurements are collected at each station. Satellite-derived sea surface temperature anomalies from MODIS Aqua validate the cruise-based observations on a spatial scale. Wind stress data from ERA5 reanalysis are correlated with thermocline shoaling and sea surface temperature anomalies to relate atmospheric forcing to observed upwelling intensity. Results are expected to document thermocline shoaling to within 10 metres of the surface and coastal sea surface temperature depressions of 4 to 6 degrees Celsius relative to offshore waters during peak upwelling. Findings contribute to understanding of fisheries productivity and climate variability in the Gulf of Guinea. Keywords: coastal upwelling, Gulf of Guinea, thermocline, Ogun State, oceanographic cruise