Seasonal and intraseasonal surface chlorophyll‐a variability along the northwest African coast
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Five years of SeaWiFS ocean color data are used to characterize the variability of surface chlorophyll (SCHL) over seasonal and intraseasonal timescales along the northwest African coast (between 10°N and 33°N). This variability is interpreted in regards of remotely sensed wind stress and sea surface temperature and of climatological surface nitrate concentration. Three regions with fairly different behaviors are identified: the region of the subtropical gyre (24°N–33°N) is characterized by a weak seasonality and chlorophyll confined at the coast. The inter‐gyre region off Cape Blanc (19°N–24°N) is characterized by a weak seasonality and a persistent large offshore extension of chlorophyll. The region of the recirculation gyre (10°N–19°N) is characterized by a strong seasonality and a large offshore extension of chlorophyll from February to May followed by an abrupt chlorophyll drop that propagates northward from May to June. The seasonal variability is well explained by the seasonal variability in wind‐forcing. Nutrient limitation is the key factor that explains the weak offshore extension of chlorophyll in the North. The chlorophyll drop in the South is attributed to the weakening of the wind‐forcing and the simultaneous advection of warm water from the South by a coastal and seasonal branch of the North Equatorial Counter Current (NECC). Intraseasonal variability is present in all regions. The cases of good correlation between the intraseasonal variability of the chlorophyll and of the wind‐forcing are found to be associated with weak chlorophyll offshore extension and large nutrient limitation.
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A wind-derived proxy indicates that upwelling persists in summer from 15 to 20°N, albeit weaker.
“One may wonder how much it contributes to the SST warming and what are the upwelling real cycle and effects, since a wind-derived proxy indicates rather that the latter persists in summer from 15 to 20 • N, albeit weaker [e.g., 3].”
From A model study of the seasonality of sea surface temperature and circulation in the Atlantic North-eastern Tropical Upwelling System (2015) · cites this paper as [3]
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On the role of the mesoscale circulation on an idealized coastal upwelling ecosystem
Lathuilière, C., Echevin, V., Lévy, M., & Madec, G. (2010) · Journal of Geophysical Research: Oceans · doi:10.1029/2009jc005827 · Cited by 63 · see citing works
Self-citationFaye, S., Lazar, A., Sow, B. A., & Gaye, A. T. (2015) · Frontiers in Physics · doi:10.3389/fphy.2015.00076 · Cited by 53 · see citing works
“It is also a major indicator of the state of the marine environment relative to phytoplankton biomass needs, particularly for upwelling zone activity, and particularly for coastal upwellings [3].”
Background
- Authors
- Lathuilière, C., Echevin, V., & Lévy, M.
- Affiliations
- Centre National de la Recherche Scientifique (FR)
- LOCEAN/IPSL, UPMC/IRD/CNRS/MNHN Paris France
- ORCID
- Lévy, M.
- Venue
- Journal of Geophysical Research: Oceans
- Publisher
- American Geophysical Union (AGU)
- Published
- 2008-05
- Volume
- 113
- Issue
- C5
- Pages
- 05007
- ISSN
- 0148-0227 (ISSN-L)
- OpenAlex
- W1981450255
- Cited by
- 135
- References
- 0
- Citations by year
- 2026: 10 · 2025: 6 · 2024: 2 · 2023: 5 · 2022: 22 · 2021: 11 · 2020: 7 · 2019: 12 · 2018: 6 · 2017: 5 · 2016: 14 · 2015: 6 · 2014: 9 · 2013: 6 · 2012: 1
- FWCI
- 3.00
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- Journal of Geophysical Research Atmospheres (publishedVersion, other-oa)
- HAL (submittedVersion, other-oa)
- Funders
- Centre National d’Etudes Spatiales
- Centre National de la Recherche Scientifique
- H2020 European Research Council
- Topics
- Physical Sciences › Earth and Planetary Sciences › Oceanography › Marine and coastal ecosystems
- Physical Sciences › Earth and Planetary Sciences › Oceanography › Oceanographic and Atmospheric Processes
- Physical Sciences › Environmental Science › Environmental Chemistry › Aquatic Ecosystems and Phytoplankton Dynamics
- Keywords
- surface chlorophyll-a, seasonal variation, intraseasonal variability, Northwest African coast, North Equatorial Countercurrent, subtropical gyre, recirculation gyre, wind forcing, nutrient limitation, surface nitrate, sea surface temperature
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