Cropper, T.E, Hanna, E and Bigg, G.R (2014) Spatial and temporal seasonal trends in coastal upwelling off Northwest Africa, 1981-2012. Deep-Sea Research Part I: Oceanographic Research Papers, 86. 94 - 111. ISSN 0967-0637
Abstract
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. © 2014 The Authors.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2014 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
Keywords: | Coastal upwelling, Africa, Wind, SST, Climate change, NAO |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Social Sciences (Sheffield) > Department of Geography (Sheffield) |
Funding Information: | Funder Grant number NERC NE/I528618/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 09 May 2014 14:10 |
Last Modified: | 09 May 2014 14:10 |
Published Version: | http://dx.doi.org/10.1016/j.dsr.2014.01.007 |
Status: | Published |
Publisher: | Elsevier |
Refereed: | Yes |
Identification Number: | 10.1016/j.dsr.2014.01.007 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:78895 |