Spatial and temporal seasonal trends in coastal upwelling off Northwest Africa, 1981–2012
Open accessAbstract
Seasonal coastal upwelling was analyzed along the NW African coastline (11–35°N) from 1981 to 2012. Upwelling magnitudes are calculated by wind speed indices, sea-surface temperature indices and inferred from meteorological station, sea-surface height and vertical water column transport data. A permanent annual upwelling regime is documented across 21–35°N and a seasonal regime across 12–19°N, in accordance with the climatology of previous studies. Upwelling regions were split into three zones: (1) the Mauritania–Senegalese upwelling zone (12–19°N), (2) the strong permanent annual upwelling zone (21–26°N) and (3) the weak permanent upwelling zone (26–35°N). We find compelling evidence in our various indices for the Bakun upwelling intensification hypothesis due to a significant coastal summer wind speed increase, resulting in an increase in upwelling-favorable wind speeds north of 20°N and an increase in downwelling-favorable winds south of 20°N. The North Atlantic Oscillation plays a leading role in modifying interannual variability during the other seasons (autumn–spring), with its influence dominating in winter. The East Atlantic pattern shows a strong correlation with upwelling during spring, while El Niño Southern Oscillation and Atlantic Multi-decadal Oscillation teleconnections were not found. A disagreement between observationally-based wind speed products and reanalysis-derived data is explored. A modification to the Bakun upwelling intensification hypothesis for NW Africa is presented, which accounts for the latitudinal divide in summer wind regimes.
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Cropper et al. (2014) found further evidence of increases in upwelling favorable winds during summer months from 1981 to 2012.
“They found further evidence of increases in upwelling favorable winds (from oceanic stations; two out of four significant) during summer months from 1981 to 2012.”
From Recent Trends in SST, Chl‐<i>a</i>, Productivity and Wind Stress in Upwelling and Open Ocean Areas in the Upper Eastern North Atlantic Subtropical Gyre (2021) · cites this paper as Cropper et al. (2014)
The Discussion reports increased summer upwelling-favorable winds north of 21°N during 1981–2012, supporting the main claim. But the cited paper’s Results (§3.3.1) describe six coastal meteorological stations, with positive trends at four and a significant trend at only one; they do not support the citing sentence’s description of oceanic stations with two of four significant. (LLM, conf=0.84)
Experimental — accuracy not yet measuredCropper et al. (2014) and Taboada and Anadón (2012) reported general SST increases in the North Atlantic, with open ocean warming rates in the range of +0.1 to +0.3 °C dec-1.
“Cropper et al. (2014) and Taboada and Anadón (2012) reported general SST increases in the North Atlantic, where warming rates in the open ocean lie in the range of +0.1-0.3°Cdec -1 .”
From Recent Trends in SST, Chl‐<i>a</i>, Productivity and Wind Stress in Upwelling and Open Ocean Areas in the Upper Eastern North Atlantic Subtropical Gyre (2021) · cites this paper as Cropper et al. (2014)
The ΔSST section reports statistically significant open-ocean warming around parts of the northwest African coast. It does not establish general SST increases across the North Atlantic or give the claimed open-ocean warming range of +0.1 to +0.3 °C per decade. (LLM, conf=0.86)
Experimental — accuracy not yet measuredThe Bakun Hypothesis was originally supported by emerging interregional patterns of observed sea-surface wind stress and has been periodically tested against time series of observed data in all four regional eastern boundary upwelling systems.
“This idea was originally supported by emerging interregional patterns of observed sea-surface wind stress, and has been periodically tested against time series of observed data in all four regional EBUS [12,13].”
From Anticipated Effects of Climate Change on Coastal Upwelling Ecosystems (2015) · cites this paper as [13]
Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.
Experimental — accuracy not yet measuredCropper et al. computed the Trade Wind Index, which suggests an intensification of winds since 1973.
“Moreover, they computed the Trade Wind Index (difference of sea level pressure from Azores and Cape Verde) which also suggests an intensification of winds since 1973.”
From Recent Trends in SST, Chl‐<i>a</i>, Productivity and Wind Stress in Upwelling and Open Ocean Areas in the Upper Eastern North Atlantic Subtropical Gyre (2021) · cites this paper as Cropper et al. (2014)
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Anticipated Effects of Climate Change on Coastal Upwelling Ecosystems
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“1E), a region that receives nutrients of the easterly boundary up-welling linked to the Canary Current (Arístegui et al., 2009; Cropper et al., 2014; Vald ´ es and D ´ eniz-Gonz ´ alez, 2015; Nieto and M ´ elin, 2017) (Fig.”
Varela, R., DeCastro, M., Rodriguez-Diaz, L., Dias, J. M., & Gómez-Gesteira, M. (2022) · Journal of Marine Science and Engineering · doi:10.3390/jmse10121970 · Cited by 9 · see citing works
- Authors
- Cropper, T. E., Hanna, E., & Bigg, G. R.
- Affiliations
- University of Sheffield (GB)
- Corresponding author
- Cropper, Thomas E.
- Venue
- Deep Sea Research Part I: Oceanographic Research Papers
- Publisher
- Elsevier BV
- Published
- 2014-04
- Volume
- 86
- Pages
- 94-111
- ISSN
- 0967-0637 (ISSN-L)
- OpenAlex
- W1964542801
- Cited by
- 260
- References
- 4
- Citations by year
- 2026: 20 · 2025: 21 · 2024: 26 · 2023: 24 · 2022: 38 · 2021: 21 · 2020: 23 · 2019: 20 · 2018: 22 · 2017: 16 · 2016: 15 · 2015: 10 · 2014: 4
- FWCI
- 10.82
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- Deep Sea Research Part I Oceanographic Research Papers (publishedVersion, cc-by)
- Lincoln Repository (University of Lincoln) (acceptedVersion)
- White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
- ORCA Online Research @Cardiff (Cardiff University) (acceptedVersion)
- NERC Open Research Archive (Natural Environment Research Council) (acceptedVersion)
- Figshare (submittedVersion, cc-by)
- Funders
- NERC Doctoral Training (NE/I528618/1)
- Department of Geography, University of Sheffield
- 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 › Oceanography › Marine and coastal ecosystems
- Keywords
- coastal upwelling, North Atlantic Oscillation, East Atlantic pattern, interannual variability, sea surface temperature, Northwest African coast, ENSO, Atlantic Multidecadal Oscillation
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