Role of interannual K elvin wave propagations in the equatorial A tlantic on the A ngola B enguela C urrent system
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The link between equatorial Atlantic Ocean variability and the coastal region of Angola‐Namibia is investigated at interannual time scales from 1998 to 2012. An index of equatorial Kelvin wave activity is defined based on Prediction and Research Moored Array in the Tropical Atlantic (PIRATA). Along the equator, results show a significant correlation between interannual PIRATA monthly dynamic height anomalies, altimetric monthly Sea Surface Height Anomalies (SSHA), and SSHA calculated with an Ocean Linear Model. This allows us to interpret PIRATA records in terms of equatorial Kelvin waves. Estimated phase speed of eastward propagations from PIRATA equatorial mooring remains in agreement with the linear theory, emphasizing the dominance of the second baroclinic mode. Systematic analysis of all strong interannual equatorial SSHA shows that they precede by 1–2 months extreme interannual Sea Surface Temperature Anomalies along the African coast, which confirms the hypothesis that major warm and cold events in the Angola‐Benguela current system are remotely forced by ocean atmosphere interactions in the equatorial Atlantic. Equatorial wave dynamics is at the origin of their developments. Wind anomalies in the Western Equatorial Atlantic force equatorial downwelling and upwelling Kelvin waves that propagate eastward along the equator and then poleward along the African coast triggering extreme warm and cold events, respectively. A proxy index based on linear ocean dynamics appears to be significantly more correlated with coastal variability than an index based on wind variability. Results show a seasonal phasing, with significantly higher correlations between our equatorial index and coastal SSTA in October–April season.
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In models, interannual variations of temperature, nitrate, and oxygen concentrations along the southwestern coast of Africa are primarily controlled by oceanic teleconnections associated with equatorial wave variability and along-shore water mass transport.
“In models, interannual variations of temperature, nitrate, and oxygen concentrations along the southwestern coast of Africa are primarily controlled by oceanic teleconnections associated with equatorial wave variability and along-shore water mass transport (Mohrholz et al., 2008;Bachèlery, 2016;Bachèlery et al., 2016a,b;Koungue et al., 2017).”
From The tropical atlantic observing system (2019) · cites this paper as Koungue et al., 2017
The Introduction reports modeling results in which equatorial remote forcing explains more than 80% of interannual coastal sea-surface temperature, nitrate, and oxygen variability. The Summary, Discussion, and Conclusions discusses advection of water masses but says its importance at interannual timescales is difficult to assess; it does not establish along-shore transport as a primary control. (LLM, conf=0.86)
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Research works printed but not linked: 26
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- Authors
- Imbol Koungue, R. A., Illig, S., & Rouault, M.
- Affiliations
- Department of Oceanography MARE Institute, University of Cape Town Cape Town South Africa
- University of Cape Town (ZA)
- Corresponding author
- Rouault, Mathieu
- Venue
- Journal of Geophysical Research: Oceans
- Publisher
- American Geophysical Union (AGU)
- Published
- 2017-06
- Volume
- 122
- Issue
- 6
- Pages
- 4685-4703
- ISSN
- 2169-9275 (ISSN-L)
- 2169-9291
- OpenAlex
- W2611752423
- Cited by
- 48
- References
- 33
- Citations by year
- 2026: 3 · 2025: 4 · 2024: 10 · 2023: 8 · 2022: 2 · 2021: 4 · 2020: 4 · 2019: 7 · 2018: 5 · 2017: 1
- FWCI
- 3.09
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Journal of Geophysical Research Oceans (publishedVersion)
- HAL (submittedVersion, other-oa)
- Institutional Archive of Ifremer (French Research Institute for Exploitation of the Sea) (submittedVersion, other-oa)
- Topics
- Physical Sciences › Earth and Planetary Sciences › Oceanography › Oceanographic and Atmospheric Processes
- Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
- Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Meteorological Phenomena and Simulations
- Keywords
- equatorial Kelvin waves, interannual variability, sea level anomalies, ocean-atmosphere interaction, wind forcing, sea surface temperature anomalies
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