River flow and ocean temperatures: The Congo River

Using a regional ocean model, the impacts of the Congo River on ocean temperatures, mixed layer depths (MLDs), and barrier layers are studied. A sensitivity simulation with no Congo flow shows that the river shallows the mixed layer by up to 7 m and creates barrier layers up to 6 m thick and temperature inversions of up to 0.5 K. Contrary to previous modeling studies, but in agreement with observational analysis, simulation results show no substantial SST signal from the Congo River in the eastern Atlantic. A cooling signal, < 0.25 K, is simulated in localized regions. A heat budget analysis shows that in these regions the cooling effect of reducing shortwave absorption within the mixed layer, by the shallowing of this layer, exceeds the warming impact of reducing vertical mixing. This is shown to be partly a consequence of the shallow mixed layer (10–15 m) in this region. The direct impact of the temperature of the Congo River input is confined to the region within1 °of the river mouth.