Abstract
A 40 year time series of daily and monthly Ekman transport is analysed in an oceanic area 150 km offshore Cape Finisterre (43°N, 11°W). The periodicity of the signal showed an annual component (365 days), a seasonal fluctuation (50 days) and a time scale related to passing storms (20 days). The Ekman transport showed different seasonal patterns. Thus, the summer pattern is characterized by transport pointing seaward (upwelling favourable) practically perpendicular to the shoreline, while the winter pattern is characterized by transport pointing landward (downwelling favourable). Although the most favourable upwelling conditions were observed during summer, for the last 15 years the frequency of observed winter upwelling events is higher due to the prevalence of northerly winds.
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Acknowledgements
This work was partially supported by Ministerio de Ciencia y Tecnología under projects REN2003-04106-C03_02/MAR and REN2003-06633-C03. We acknowledge D. Gerardo Casas (IEO) to maintain the Ekman transport serie and Regional Weather Forecast Agency (METEOGALICIA) for kindly providing wind data.