Dynamics of a “low‐enrichment high‐retention” upwelling center over the southern Senegal shelf
Open accessAbstract
Senegal is the southern tip of the Canary upwelling system. Its coastal ocean hosts an upwelling center which shapes sea surface temperatures between latitudes 12° and 15°N. Near this latter latitude, the Cape Verde headland and a sudden change in shelf cross‐shore profile are major sources of heterogeneity in the southern Senegal upwelling sector (SSUS). SSUS dynamics is investigated by means of Regional Ocean Modeling System simulations. Configuration realism and resolution (Δ x ≈ 2 km) are sufficient to reproduce the SSUS frontal system. Our main focus is on the 3‐D upwelling circulation which turns out to be profoundly different from 2‐D theory: cold water injection onto the shelf and upwelling are strongly concentrated within a few tens of kilometers south of Cape Verde and largely arise from flow divergence in the alongshore direction; a significant fraction of the upwelled waters are retained nearshore over long distances while travelling southward under the influence of northerly winds. Another source of complexity, regional‐scale alongshore pressure gradients, also contributes to the overall retention of upwelled waters over the shelf. Varying the degree of realism of atmospheric and oceanic forcings does not appreciably change these conclusions. This study sheds light on the dynamics and circulation underlying the recurrent sea surface temperature pattern observed during the upwelling season and offers new perspectives on the connections between the SSUS physical environment and its ecosystems. It also casts doubt on the validity of upwelling intensity estimations based on simple Ekman upwelling indices at such local scales.
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In many upwelling sectors, alongshore pressure gradients can yield onshore velocities that counteract, or more infrequently reinforce, the Ekman flow.
“In many upwelling sectors they can yield onshore velocities that counteract, or more infrequently reinforce, the Ekman flow (Colas et al. 2008;Marchesiello et al. 2010;Ndoye et al. 2017;Jacox et al. 2018).”
From Competition between Baroclinic Instability and Ekman Transport under Varying Buoyancy Forcings in Upwelling Systems: An Idealized Analog to the Southern Ocean (2021) · cites this paper as Ndoye et al. 2017
Section 3.3 reports that alongshore gradients produce onshore geostrophic flow over the southern Senegal shelf, reducing or reversing the offshore flow expected from Ekman transport. The paper does not establish that this happens in many upwelling sectors, or that reinforcement of Ekman flow occurs less frequently. Page numbers are not available in our copy. (LLM, conf=0.86)
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Thomsen, S., Capet, X., & Echevin, V. (2021) · Journal of Physical Oceanography · doi:10.1175/jpo-d-20-0294.1 · Cited by 17 · see citing works
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- Authors
- Ndoye, S., Capet, X., Estrade, P., Sow, B., Machu, E., Brochier, T., Döring, J., & Brehmer, P.
- Affiliations
- Centre National de la Recherche Scientifique (FR)
- Cheikh Anta Diop University (SN)
- Ziguinchor University (SN)
- LPAO‐SF University of Dakar Dakar Senegal
- Unité de Modélisation Mathématique et Informatique des Systèmes Complexes (FR)
- Leibniz Centre for Tropical Marine Research (DE)
- Corresponding author
- Ndoye, Siny
- Venue
- Geophysical Research Letters
- Publisher
- American Geophysical Union (AGU)
- Published
- 2017-05-28
- Volume
- 44
- Issue
- 10
- Pages
- 5034-5043
- ISSN
- 0094-8276 (ISSN-L)
- 1944-8007
- OpenAlex
- W2607908178
- Cited by
- 61
- References
- 1
- Citations by year
- 2026: 6 · 2025: 4 · 2024: 8 · 2023: 7 · 2022: 10 · 2021: 9 · 2020: 4 · 2019: 7 · 2018: 6
- FWCI
- 3.09
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Geophysical Research Letters (publishedVersion)
- HAL (submittedVersion, other-oa)
- Funders
- IRD through the AWA and LMI ECLAIRS programs
- LEFE-INSU FUSE
- European Union FP7 PREFACE
- Programme Doctoral International Modelisation des Systemes Complexes UPMC/IRD
- Topics
- Physical Sciences › Earth and Planetary Sciences › Oceanography › Oceanographic and Atmospheric Processes
- Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Meteorological Phenomena and Simulations
- Physical Sciences › Earth and Planetary Sciences › Earth-Surface Processes › Aquatic and Environmental Studies
- Keywords
- coastal upwelling, northerly winds, alongshore pressure gradient, sea surface temperature, atmospheric forcing, ocean modeling
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