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Cited by 59Oceanographic and Atmospheric ProcessesClimate variability and modelsMeteorological Phenomena and Simulations

Cross-equatorial structure and temporal modulation of intraseasonal variability at the surface of the Tropical Atlantic Ocean.

Open access
Athie, Gabriela, Marin, Frédéric·2008·Journal of Geophysical Research: Oceans
DOI 10.1029/2007jc004332
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Abstract

Intraseasonal variability (10–50 days) in the equatorial Atlantic Ocean is analyzed from multiyear (1999–2005) satellite gridded products of sea‐level anomalies (SLA) and sea‐surface temperature (SST). Two regions with distinct intraseasonal variability have been identified. The first one, west of 10°W, is dominated by westward‐propagating anomalies, with maximum values in SLA along 5°N and in SST along 2°N: They occur in boreal summer with periods of 25–50 days and are known to correspond to tropical instability waves (TIWs). We show that TIWs have also a signature, though weaker, south of the equator, especially along 5°S, in SLA. Northern and southern anomalies propagate together westward, being mostly out of phase, suggesting that equatorial wave dynamics is involved in TIWs variability. An SST signature of TIWs is also observed near 2°S, in quadrature with SST anomalies detected in the Northern Hemisphere. The interannual modulations of the TIW signature in SLA and SST are compared and discussed. The second dominant intraseasonal signal is only seen east of 10°W in SST and corresponds to an equatorially trapped variability, confined to the Gulf of Guinea with periods between 10 and 20 days. This signal is present in boreal summer when an intense SST front is observed just north of the equator. Intraseasonal variability with comparable periods is also observed in the meridional wind stress throughout the year. Comparison of SST and meridional wind stress anomalies suggests that the 10‐ to 20‐day variability in SST is forced by the wind stress but seasonally modulated by the presence of the SST front.

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Registry

Crossref · 10.1029/2007jc004332

Cites

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  • Tropical instability waves dominate the intraseasonal variability in the western and central equatorial Atlantic, while wind-forced waves dominate in the east.

    “no such study is available in the equatorial Atlantic where TIW dominate the intraseasonal variability in the western and central basins and wind forced waves dominate in the east (Athié and Marin, 2008).”

    From Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue (2020) · cites this paper as Athié and Marin, 2008

    Section 3.3 identifies TIW-period variability in the central basin, and the Summary and Conclusion (§6) describes an eastern equatorial 15-day SST signal locally forced by wind stress. But §3.3 attributes the dominant variability west of 30°W to North Equatorial Countercurrent meanders rather than TIWs, so the claim overextends TIW dominance to the western basin. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • TIW are observed west of 10° W at periods between 20 and 50 days.

    “TIW are observed west of 10° W at periods between 20 and 50 days (Jochum et al., 2004;Athié and Marin, 2008;Jouanno et al., 2013).”

    From Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue (2020) · cites this paper as Athié and Marin, 2008

    The Summary and Conclusion (§6, paragraph 54) places the dominant SST signature of TIWs west of 10°W. The Introduction (§1, paragraph 3) reports observed TIW periods of 15–50 days, while the paper’s own analysis uses a 25–50-day band (§3.3, paragraph 32). Neither gives 20 days as the lower bound attributed in the claim. (LLM, conf=0.82)

    Experimental — accuracy not yet measured

  • East of 10° E, the impacts of wind forced equatorial waves superimpose at different frequencies: Kelvin waves at periods between 25 and 40 days, mixed Rossby-gravity waves between 15 and 20 days, and inertia-gravity waves between 5 and 11 days.

    “East of 10° E, the impacts of wind forced equatorial waves superimpose at different frequencies (Houghton and Colin, 1987;Athié et al., 2008;de Coëtlogon et al., 2010;Jouanno et al., 2013;Herbert and Bourlès, 2018): Kelvin waves at periods between 25 and 40 days, mixed Rossby-gravity waves between 15 and 20 days, and inertia-gravity waves between 5 and 11 days.”

    From Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue (2020) · cites this paper as Athié et al., 2008

    The Introduction (§1, paragraphs 2 and 8; page unavailable) describes wind-forced variability near 15 days and relates 10–20-day variability to mixed Rossby–gravity waves. The dominant-period analysis (§3.3, paragraph 30) finds overlapping 10–20-day and 25–50-day signals along the equator, but does not identify the longer-period signal as Kelvin waves. Our copy does not support the claimed 5–11-day inertia–gravity waves or locate this combination east of 10°E. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • On intraseasonal timescales, variability in the equatorial Atlantic is dominated by TIWs in the western and central part and by wind-driven waves in the east.

    “On intraseasonal timescales, variability in the equatorial Atlantic is dominated by TIWs in the western and central part and by wind-driven waves in the east (Athie and Marin, 2008).”

    From The tropical atlantic observing system (2019) · cites this paper as Athie and Marin, 2008

  • One reason the conclusion on the nature of intraseasonal processes affecting the nitrate budget east of 10° W is not straightforward could be that the low frequency signal captures part of the Kelvin wave induced variability as there is no sharp cutoff at 30 days in the spectrum of Kelvin waves.

    “One reason could be that the low frequency signal captures part of the Kelvin wave induced variability as there is no sharp cutoff at 30 days in the spectrum of Kelvin waves (Athié and Marin, 2008;Athié et al., 2009;Jouanno et al., 2013).”

    From Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue (2020) · cites this paper as Athié and Marin, 2008

    Section 3.3 reports SST variability east of 10°W in 10–20-day and 25–50-day bands, but does not identify it as Kelvin-wave variability. Searches for Kelvin waves and a 30-day spectral cutoff found no passage addressing whether lower-frequency signals capture Kelvin-wave variability; the paper also does not address the nitrate budget. The indexed passages provide section labels but no page numbers. (LLM, conf=0.76)

    Experimental — accuracy not yet measured

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Cites

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Research works printed but not linked: 1

  1. Challenor, P. Cipollini, and D. Cromwell (2001), Use of the 3-D Radon Transform to examine the properties of oceanic Rossby waves, J. Atmos. Ocean. Technol., 18(9), 1558 -1566.

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Authors
Athie, G., & Marin, F.
Affiliations
  • LEGOS‐UMR, CNRS/CNES/IRD/UPS Centre IRD de Bretagne Plouzané France
  • Centre National de la Recherche Scientifique (FR)
ORCID
Marin, Frédéric
Venue
Journal of Geophysical Research: Oceans
Publisher
American Geophysical Union (AGU)
Published
2008-08
Volume
113
Issue
C8
Pages
C08020
ISSN
0148-0227 (ISSN-L)
DOI
10.1029/2007jc004332
OpenAlex
W2053852444
Cited by
59
References
41
Citations by year
2026: 2 · 2025: 2 · 2024: 5 · 2023: 7 · 2022: 5 · 2021: 3 · 2020: 3 · 2019: 3 · 2018: 2 · 2017: 1 · 2016: 2 · 2015: 2 · 2014: 5 · 2013: 4 · 2012: 5
FWCI
1.86
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of Geophysical Research Atmospheres (publishedVersion, other-oa)
  • HAL (submittedVersion, other-oa)
Funders
  • National Aeronautics and Space Administration
  • Centre National d’Etudes Spatiales
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
intraseasonal variability, equatorial Atlantic, tropical instability waves, sea level anomalies, sea surface temperature, equatorial waves, Gulf of Guinea, SST fronts, boreal summer

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