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Wind-induced variability in the Northern Current (northwestern Mediterranean Sea) as depicted by a multi-platform observing system

Abstract : The variability and evolution of the Northern Current (NC) in the area off Toulon is studied for 2 weeks in December 2011 using data from a glider, a high-frequency (HF) radar network, vessel surveys, a weather station, and an atmospheric model. The NC variability is dominated by a synoptic response to wind events, even though the dataset also evidences early stages of transition from late summer to fall-winter conditions. With weak winds, the current is mostly zonal and in geostrophic balance even at the surface, with a zonal transport associated with the NC of ≈1 Sv. Strong westerly wind events (longer than 2-3 days) induce an interplay between the direct-wind-induced ageostrophic response and the geostrophic component: upwelling is observed, with offshore surface transport, surface cooling, flattening of the isopycnals, and reduced zonal geostrophic transport (0.5-0.7 Sv). The sea surface response to wind events, as observed by the HF radar, shows total currents rotated at ≈ -55 to 90° to the right of the wind. Performing a decomposition between geostrophic and ageostrophic components of the surface currents, the wind-driven ageostrophic component is found to rotate by ≈ -25 to -30° to the right of the wind. The ageostrophic component magnitude corresponds to ≈2 % of the wind speed.
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Contributor : Nathalie Pothier Connect in order to contact the contributor
Submitted on : Saturday, May 14, 2022 - 8:41:45 AM
Last modification on : Monday, May 16, 2022 - 3:03:53 AM


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Maristella Berta, Lucio Bellomo, Annalisa Griffa, Marcello G. Magaldi, Anne Molcard, et al.. Wind-induced variability in the Northern Current (northwestern Mediterranean Sea) as depicted by a multi-platform observing system. OCEAN SCIENCE, 2018, 14, pp.689-710. ⟨10.5194/os-14-689-2018⟩. ⟨insu-03668088⟩



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