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Eastern boundary circulation and hydrography off Angola – building Angolan oceanographic capacities.

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Tchipalanga, P., Dengler, M., Brandt, P., Kopte, R., Macuéria, M., Coelho, P., Ostrowski, M., Keenlyside, N. S.·2018·Bulletin of the American Meteorological Society
DOI 10.1175/bams-d-17-0197.1
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Abstract

The eastern boundary region off Angola encompasses a highly productive ecosystem important for the food security of the coastal population. The fish-stock distribution, however, undergoes large variability on intraseasonal, interannual, and longer time scales. These fluctuations are partly associated with large-scale warm anomalies that are often forced remotely from the equatorial Atlantic and propagate southward, reaching the Benguela upwelling off Namibia. Such warm events, named Benguela Niños, occurred in 1995 and in 2011. Here we present results from an underexplored extensive in situ dataset that was analyzed in the framework of a capacity-strengthening effort. The dataset was acquired within the Nansen Programme executed by the Food and Agriculture Organization of the United Nations and funded by the Norwegian government. It consists of hydrographic and velocity data from the Angolan continental margin acquired biannually during the main downwelling and upwelling seasons over more than 20 years. The mean seasonal changes of the Angola Current from 6° to 17°S are presented. During austral summer the southward Angola Current is concentrated in the upper 150 m. It strengthens from north to south, reaching a velocity maximum just north of the Angola Benguela Front. During austral winter the Angola Current is weaker, but deeper reaching. While the southward strengthening of the Angola Current can be related to the wind forcing, its seasonal variability is most likely explained by coastally trapped waves. On interannual time scales, the hydrographic data reveal remarkable variability in subsurface upper-ocean heat content. In particular, the 2011 Benguela Niño was preceded by a strong subsurface warming of about 2 years’ duration.

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  • Many data products poorly represent the atmospheric and oceanic circulations in the Benguela region.

    “Many data products poorly represent the atmospheric and oceanic circulations in the region (Large and Yeager, 2008;Patricola and Chang, 2017;Tchipalanga et al., 2018), underscoring the need for updated products at higher resolution.”

    From The tropical atlantic observing system (2019) · cites this paper as Tchipalanga et al., 2018

    The Summary and Discussion (page not available) reports substantial biases in simulated ocean-current velocity structures and upwelling strength, as well as large salinity biases in several ocean reanalysis products. It does not establish that data products also poorly represent atmospheric circulation in the Benguela region. (LLM, conf=0.85)

    Experimental — accuracy not yet measured

  • Much of the present observing system was designed before coupled model biases emerged as a scientific research priority; as a result, efforts to alleviate model biases are hampered by inadequate in situ measurements.

    “Much of the present observing system was designed before coupled model biases emerged as a scientific research priority.As a result, efforts to alleviate model biases are hampered by inadequate in situ measurements (Tchipalanga et al., 2018).”

    From The tropical atlantic observing system (2019) · cites this paper as Tchipalanga et al., 2018

    In “History of Physical Oceanography in Angola” (page unavailable), the paper says a lack of observations prevents satisfactory evaluation of model simulations along the Angolan margin. Its “Summary and Discussion” (page unavailable) links better observations and process understanding to reducing model biases. It does not say that the observing system was designed before coupled-model biases became a research priority, and its discussion is regional rather than a claim about much of the present observing system. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • Relatively little is known about the vertical structure and seasonality of the poleward Angola current, though data from recently deployed buoys are beginning to shed light on it.

    “Relatively little is known about the vertical structure and seasonality of the poleward Angola current (Tchipalanga et al., 2018), though data from recently deployed buoys in the region are beginning to shed some light on this (Kopte et al., 2017).”

    From The tropical atlantic observing system (2019) · cites this paper as Tchipalanga et al., 2018

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Authors
Tchipalanga, P., Dengler, M., Brandt, P., Kopte, R., Macuéria, M., Coelho, P., Ostrowski, M., & Keenlyside, N. S.
Affiliations
  • Instituto Nacional de Investigação Pesqueira (AO)
  • Bjerknes Centre for Climate Research (NO)
  • Christian-Albrechts-Universität zu Kiel (DE)
Corresponding author
  • Dengler, M.
  • Kopte, R.
  • Macuéria, M.
  • Ostrowski, M.
ORCID
Venue
Bulletin of the American Meteorological Society
Publisher
American Meteorological Society
Published
2018-08
Volume
99
Issue
8
Pages
1589-1605
ISSN
  • 0003-0007 (ISSN-L)
  • 1520-0477
DOI
10.1175/bams-d-17-0197.1
OpenAlex
W2793141783
Cited by
49
References
4
Citations by year
2026: 2 · 2025: 8 · 2024: 5 · 2023: 7 · 2022: 2 · 2021: 11 · 2020: 5 · 2019: 7 · 2018: 2
FWCI
16.70
Type
journal article
Language
en
Open access
Locations
  • Bulletin of the American Meteorological Society (publishedVersion)
  • Helmholtz Centre for Ocean Research Kiel (GEOMAR) (acceptedVersion, other-oa)
  • NORA - Norwegian Open Research Archives (submittedVersion, cc-by)
  • NORA - Norwegian Open Research Archives (submittedVersion, other-oa)
Funders
European Commission (603521)
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 › Environmental Science › Global and Planetary Change › Marine and fisheries research
Keywords
Angola Current, Benguela Niño, Angola-Benguela Front, seasonal variation, coastal trapped waves, wind forcing, interannual variability, hydrographic variability, Benguela upwelling

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