Publications des scientifiques de l'IRD

Benazzouz A., Pelegri J. L., Demarcq Hervé, Machin F., Mason E., Orbi A., Pena-Izquierdo J., Soumia M. (2014). On the temporal memory of coastal upwelling off NW Africa. Journal of Geophysical Research : Oceans, 119 (9), p. 6356-6380. ISSN 2169-9275.

Titre du document
On the temporal memory of coastal upwelling off NW Africa
Année de publication
2014
Type de document
Article référencé dans le Web of Science WOS:000343879200044
Auteurs
Benazzouz A., Pelegri J. L., Demarcq Hervé, Machin F., Mason E., Orbi A., Pena-Izquierdo J., Soumia M.
Source
Journal of Geophysical Research : Oceans, 2014, 119 (9), p. 6356-6380 ISSN 2169-9275
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.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020] ; Limnologie physique / Océanographie physique [032] ; Télédétection [126]
Description Géographique
ATLANTIQUE NORD EST, CAP VERT ; CANARIES ILES ; AFRIQUE DE L'OUEST ; AFRIQUE DU NORD ; MAROC ; GIBRALTAR ; CADIX GOLFE
Localisation
Fonds IRD [F B010062662]
Identifiant IRD
fdi:010062662
Contact