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Auteur (up) Benazzouz, A.; Pelegri, J.L.; Demarcq, H.; Machin, F.; Mason, E.; Orbi, A.; Pena-Izquierdo, J.; Soumia, M.
Titre On the temporal memory of coastal upwelling off NW Africa Type Article scientifique
Année 2014 Publication Revue Abrégée J. Geophys. Res.-Oceans
Volume 119 Numéro 9 Pages 6356-6380
Mots-Clés atlantic; Canary Current; cape blanc region; circulation; Coastal upwelling; eastern boundary; Ekman transport; interannual variability; northwest africa; NW Africa; sea-surface temperature; SST difference; system; temporal memory; water
Résumé We use a combination of satellite, in situ, and numerical data to provide a comprehensive view of the seasonal coastal upwelling cycle off NW Africa in terms of both wind forcing and sea surface temperature (SST) response. Wind forcing is expressed in terms of both instantaneous (local) and time-integrated (nonlocal) indices, and the ocean response is expressed as the SST difference between coastal and offshore waters. The classical local index, the cross-shore Ekman transport, reproduces reasonably well the time-latitude distribution of SST differences but with significant time lags at latitudes higher than Cape Blanc. Two nonlocal indices are examined. One of them, a cumulative index calculated as the backward averaged Ekman transport that provides the highest correlation with SST differences, reproduces well the timing of the SST differences at all latitudes (except near Cape Blanc). The corresponding time lags are close to zero south of Cape Blanc and range between 2 and 4 months at latitudes between Cape Blanc and the southern Gulf of Cadiz. The results are interpreted based on calculations of spatial and temporal auto and cross correlations for wind forcing and SST differences. At temporal scales of 2-3 weeks, the alongshore advection of alongshore momentum compensates for interfacial friction, allowing the upwelling jet and associated frontal system to remain active. We conclude that the coastal jet plays a key role in maintaining the structure of coastal upwelling, even at times of relaxed winds, by introducing a seasonal memory to the system in accordance with the atmospheric-forcing annual cycle.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 2169-9275 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1194
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Auteur (up) Quispe-Ccalluari, C.; Tam, J.; Demarcq, H.; Chamorro, A.; Espinoza-Morriberon, D.; Romero, C.; Dominguez, N.; Ramos, J.; Oliveros-Ramos, R.
Titre An index of coastal thermal effects of El Nino Southern Oscillation on the Peruvian Upwelling Ecosystem Type Article scientifique
Année 2018 Publication Revue Abrégée Int. J. Climatol.
Volume 38 Numéro 7 Pages 3191-3201
Mots-Clés climate; coastal index; eastern tropical pacific; enso; Equatorial Pacific Ocean; events; ocean; Peruvian Upwelling Ecosystem; sea-surface temperature; wind
Résumé The Peruvian Upwelling Ecosystem (PUE) is one of the most productive ecosystem in the world in terms of productivity and fish catches, partly because its geographical location is affected by remote physical processes, such as the interannual climate variability of the Equatorial Pacific Ocean (EPO), whose dominant signal is El Nino Southern Oscillation (ENSO). In order to assess the thermal effects of ENSO off Peru, a Peruvian Coastal Thermal Index (PCTI) was developed representing 87.7% of the total variation of the Sea Surface Temperature (SST) anomalies of the PUE. Between 1982 and 2014, the PCTI detected 12 warm periods and 16 cold periods in the PUE. PCTI had a linear trend component, a low frequency component and a noise component, with 1.5%, 94.5% and 4% contributions to the total variance, respectively. Wavelet analysis of PCTI showed significant peaks of variability between the years 1996 and 1999 between periods of 0.4 and 6 years. A regime shift in variance of PCTI was detected in 1999, with a lower variance between 1999 and 2014 than between 1982 and 1998, which agreed with the start of a cold phase of the Pacific Decadal Oscillation. The decrease of variance of the PCTI could be linked to an increase of the local winds associated with a higher intensity of the average state of South Pacific Anticyclone. This atmospheric change might have strengthened the coastal upwelling and counteracted the intensity of warm periods in the PUE. Finally, the comparison of different indexes allowed to detect four periods where neutral conditions occurred in the EPO while warm periods occurred in the PUE (1993, 2008, 2012 and 2014); and 1 period where a warm episode occurred in the EPO (2004-2005) while a neutral condition occurred in the PUE.
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Auteur institutionnel Thèse
Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0899-8418 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2391
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