Abstract
The interrannual variability of coastal sea surface temperature (SST) anomalies confined off Senegal is explored from a new viewpoint of the ocean-land-atmosphere interaction. The phenomenon may be classified into “coastal Niño/Niña” in the North Atlantic as discussed recently in the Northeastern Pacific and Southeastern Indian Oceans. The interannual variability of the regional mixed-layer temperature anomaly that evolves in boreal late fall and peaks in spring is associated with the alongshore wind anomaly, mixed-layer depth anomaly and cross-shore atmospheric pressure gradient anomaly, suggesting the existence of ocean-land-atmosphere coupled processes. The coupled warm (cold) event is named Dakar Niño (Niña). The oceanic aspect of the Dakar Niño (Niña) may be basically explained by anomalous warming (cooling) of the anomalously thin (thick) mixed-layer, which absorbs shortwave surface heat flux. In the case of Dakar Niña, however, enhancement of the entrainment at the bottom of the mixed-layer is not negligible.
Highlights
The interrannual variability of coastal sea surface temperature (SST) anomalies confined off Senegal is explored from a new viewpoint of the ocean-land-atmosphere interaction
This particular feature may be due to a combination of remote forcing associated with the latitudinal migration of the Inter-Tropical Convergence Zone (ITCZ), internal variability related to seasonality of the southward Canary Current, and the Dakar (Guinea) Dome[26,27,28]
The present work has investigated the interannual variability of the sea surface temperatures of the coast off Senegal from a new viewpoint of coastal Niño/Niña, which was recently introduced to explain regional climate modes confined along eastern boundaries of other basins[3,23,24], and has shown the existence of a similar ocean-land-atmosphere coupled phenomenon for the first time in the region of interest
Summary
The interrannual variability of coastal sea surface temperature (SST) anomalies confined off Senegal is explored from a new viewpoint of the ocean-land-atmosphere interaction. Along the coast of Senegal, northerly winds transport coastal surface water into the interior ocean[12] This is counterbalanced by upwelled cold and nutrient-rich water[10], generating one of the major eastern boundary upwelling systems[6], with an estimated primary production above 500 mgC m−2 d−1 in the region[13]. The total landings of sardines (Sardinella maderensis and Sardinella aurita) for Senegal varied between 59 kt and 268 kt[15] These fluctuations may be seen as the results of the combination of changes in the exploitation techniques as well as in the natural variability of the upwelling intensity[4,16]. Meridional shift of the trade winds, due to the seasonal migration of the Inter-Tropical Convergence Zone (ITCZ), induces seasonal variations in the upwelling system[6,8,9,12,17,18,19,20] along the eastern boundary
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