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Depth-longitude section of meridional velocity along a) 13°N and b) 14°N for the S hfw simulation. All quantities are climatological averages over the February-April upwelling period.
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The regional ocean circulation along the Southern Senegal shelf is studied using a numerical model for varying forcing fields during the upwelling season (November-May). The main objective is to study the shelf circulation of the marine environment in the Southern Senegal Upwelling Shelf (SSUS), the Lagrangian pathways by which waters are transport...
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... description of the mean modeled circulation are complemented by presenting vertical cross-shore sections of alongshore currents at the two cross-shore sections (13°N and 14°N), which are compared to a meridional subinertial currents over the entire deployment period during UPSEN2 . Figure 3 shows the results for these 2 cross-shore sections of S hfw simulation which warm bias is slighly reduced. The main characteristics of the meridional current are well reproduced. ...
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Citations
... In the configuration used here, the parent grid covering 7-35°N and 30-10°W has a resolution of 10 km, and the child grid used in the Senegal region (12-18°N, 20-15°W) has a resolution of 2 km. More details on the model configuration can be found in Ndoye et al. (2018). Daily outputs from the Mercator model output at 1/12°resolution (GLOBAL_ANALYSISFORECAST_PHY_001_024; downloaded from http://marine.copernicus.eu/, ...
... Hourly atmospheric forcings (air temperature, relative humidity, 10 m wind, radiative fluxes) from the ERA5 reanalysis (see below) are used in all simulations. No surface salinity restoring with climatological observations (e.g., Ndoye et al., 2018) is used. ...
In tropical regions, the freshwater flux entering the ocean originates primarily from precipitation and, to a lesser extent when considering basin-scale averages, from continental rivers. Nevertheless, at the regional scale, river flows can have a significant impact on the surface ocean dynamics. Riverine freshwater modifies salinity and, therefore, density, stratification, and circulation. With its particular coastline and high cumulative river discharge, as well as its being in the vicinity of the intertropical convergence zone (ITCZ), the eastern part of the North Tropical Atlantic (e-NTA) region off northwestern Africa is a particularly interesting location to study the linkage between precipitation, river outflow, and sea surface salinity (SSS). Here, we focus on the regional e-NTA SSS seasonal cycle and interannual variability and on the impact of using various river runoff and precipitation forcing data sets to simulate SSS with a regional model. The simulated SSS values are compared with the Climate Change Initiative (CCI) satellite SSS values; in situ SSS values from Argo floats, ships, and a coastal mooring; and the GLORYS reanalysis SSS values. An analysis of the mixed-layer salinity budget is then conducted. Overall, the simulations reproduce the seasonal cycle and interannual variability well despite a positive mean model bias north of 15° N. The seasonal cycle is impacted by the phasing of the different runoff products. The mixed-layer SSS decrease during the rainy season is mainly driven by precipitation followed by runoff by means of horizontal advection and is partly compensated for by vertical mixing. In terms of interannual anomalies, river runoff has a more direct impact on SSS than precipitation. This study highlights the importance of properly constraining river runoff and precipitation to simulate realistic SSS values and the importance of observing SSS in coastal regions to validate such constraints.
... Village officials suggested higher sea water salinisation and temperature among key factors (Interviews 5A; 5B). This observation is supported by recent studies indicating that rising surface water temperatures and ocean acidification alter species' reproduction and migration, thereby affecting biodiversity (USAID 2023;Ndoye et al. 2018;Sylla et al. 2019). 12 In this context, 'climatic anomalies at sea have aggravated an already worrying situation' (Interview 19). ...
This article examines the complex relationship between climate change and migration in Africa, with a specific focus on Senegal—a West African nation increasingly vulnerable to climate threats such as drought, rising sea levels, floods, and salinisation. As a significant origin country for irregular migration to the European Union (EU), Senegal presents a compelling case study to explore how extreme climatic conditions interact with other migration drivers. This article does not aim to quantify or measure the extent to which climatic factors and variability contributed to migration decisions. Instead, building on original empirical material, it seeks to map and explore how climate variability interacts with other migration drivers, either by amplifying them or acting in synergy with them, thereby offering a fresh perspective of the complex dynamics at play. Additionally, this article investigates the extent to which the EU addresses and integrates climate considerations into its policy responses to address migratory flows and people’s vulnerability in countries of origin. This analysis reveals that the integration of climate factors as an amplifier and a synergist is a ‘missing link’ in the EU approach in the case of Senegal, with significant implications in terms of the effectiveness and long-term sustainability of EU action.
... In the present study, the model was run with two different precipitation datasets and two different river runoff products, which are detailed in the following. No surface salinity restoring to climatological observations 155 (e.g., Ndoye et al. (2018)) was used. ...
In tropical regions, the fresh water flux entering the ocean originates primarily from precipitation and, to a lesser extent when considering basin scale averages, from continental rivers. Nevertheless, at regional scale, river flows can have a significant impact on the surface ocean dynamics. Riverine fresh water modifies salinity, and therefore density, stratification and circulation. With its particular coastline, relatively high cumulative river discharge, and the vicinity of Inter Tropical Convergence Zone (ITCZ), the eastern Southern North Tropical Atlantic (e-SNTA) region off Northwest Africa is a particularly interesting location to study the linkage between precipitations, river outflows and Sea Surface Salinity (SSS). Here we focus on the regional e-SNTA SSS seasonal cycle and interannual variability. We quantify the impact of river runoff and precipitation on SSS by means of regional simulations forced by different interannual and climatological river runoffs and precipitation products. The simulated SSS are compared with the Climate Change Initiative (CCI) SSS, in situ SSS from Argo, ships and a coastal mooring, and the GLORYS reanalysis SSS. The analysis of the salinity balance in the mixed layer is conducted to explore the dynamics influencing the SSS variability. Overall, the simulations reproduce well the seasonal cycle and interannual variability despite a positive mean model bias north of 15N. The seasonal cycle is impacted by the phasing of the different runoff products. The mixed layer SSS decrease during the rainy season is mainly driven by precipitation followed by runoff by means of horizontal advection and partly compensated by vertical mixing. In terms of interannual anomalies, river runoffs have a more direct impact on SSS than precipitation. This study highlights the importance of properly constraining river runoff and precipitation to simulate realistic SSS, and the importance of observing SSS in coastal regions to validate such constraints.
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... High K values for most target species at the Cap de Naze, Mbodiè ne-Ngazobil, and Diakhanor-Sangomar sites could be explained by the advection of upwelled waters arriving in these areas (Capet et al., 2017;Ndoye et al., 2018). To this, could also be added the quality and availability of food in the Petite Côte, an area recognized as one of the richest in primary and secondary production (Diadhiou et al., 2017;Ndour et al., 2018), and very favorable to small pelagics (Diankha et al., 2018). ...
Better management of coastal marine resources generally requires good knowledge of habitats and resources. This need led to the performance of an identification and bioecological characterization study of critical sites for small pelagics in the Senegalese coastal marine zone. Biological and ecological data were collected using beach seines (12 to 28 mm mesh) and surface drifting gillnets (28 to 36 mm mesh) at sites identified by fishermen on the basis of surveys. The results of the study highlight the bioecological characteristics of these sites: (i) the Port-Baie Hann site - a nursery and spawning site with a high diversity for the target species; it is under marine pollution threat; (ii) the Mbodiène-Ngazobil site, with high diversity for target species and the Kafountine-Cap site are nursery and spawning sites under high fishing pressure, (iii) the Diakhanor-Sangomar site - a spawning site under the potential threat of exploration of offshore Sangomar oil in addition to the high fishing pressure. This work is a first flagship contribution to a process that should lead to the development and control of new tools for the effective and sustainable management of small pelagics at national and regional scales.
Cette étude s’intègre dans la continuité de l’effort entrepris depuis quelques années pour avoir des connaissances assez fines de la circulation le long des côtes sénégalaises, notamment sur la Côte Sud du Sénégal (CSS) et de sa variabilité. À cet effet, deux simulations aux forçages aux frontières océaniques différents issues du modèle hydrodynamique régionale (ROMS) à haute résolution (2 km) ont été utilisées. L’analyse approfondie des simulations numériques montre que le modèle (ROMS) est capable de reproduire la structure et la variabilité spatio-temporelle des variables océaniques telles que la SST, la SSH et la structure des courants méridiens. La circulation océanique côtière au sud du Sénégal est globalement cohérente avec la circulation typique dans un système d’upwelling de bord est. Elle montre un faible courant cross- shore dirigé vers le large (dérive d’Ekman) de novembre à mai et un courant orienté vers la côte sur le reste de la période. La circulation alongshore met en évidence un sous-courant dont le cœur se situe sur le talus continental entre 60 m et 100 m de profondeur. La saisonnalité du sous-courant est bien reproduite avec deux pics de maximum de courant entre avril et mai et entre octobre et novembre. L’étude de la variabilité interannuelle met en évidence l’intensification et la relaxation de l’upwelling sur la CSS. Elle montre que les paramètres physiques sont sensibles aux phénomènes ENSO. Un événement « El Niño » occasionne sur la CSS un réchauffement des eaux océaniques et un ralentissement du jet côtier. Le phénomène inverse est observé lors d’un épisode « La Niña » avec cette fois-ci un approfondissement de la couche mélangée.
Despite the ecological role of dry forest, the contribution of dry forest for climate change adaptation is overlooked. Hence, the objective of this study was to assess the socioeconomic contribution of dry forests and forest products to climate change adaptation in Tigray region, Ethiopia. A total of 170 households, 15 key informants and one focus group from the existing three dry forest vegetation type were surveyed. For this study, an integrated qualitative and quantitative data analysis approach was used. More than 94% of the total household visited at least once a month to access the forest and forest products. There is Significant difference in terms of dry forest income (p < 0.05). Overall, dry forest contributes about 16.8% of the total household income. Dryland forest income reduced the area between the line of equality and the Lorenz curve, and the Gini- Coefficient by 21% in dry evergreen Afromontane forest users, 3.02% in Combretum-Terminalia woodland users and 3% Acacia-Commiphora woodlands users. Gender, occupation, wealth status and distance of the forest from their house were variables that significantly affected the income level from Combretum-Terminalia woodland users. Age of the respondent in Acacia-Commiphora woodlands users while family size of the household in dry evergreen Afromontane forest users influenced dry forest income level. Therefore, dry forest income has been becoming crucial livelihood strategy in response to the changed climate in the study area.
