Interaction of dense dense shelf water cascading and open-sea convection in the Northwestern Mediterranean during winter 2012

International audience; The winter of 2012 experienced peculiar atmospheric conditions that triggered a massive formation of dense water on the continental shelf and in the deep basin of the Gulf of Lions. Multi-platforms observations enabled, with an unprecedented resolution, a synoptic view of dense water formation and spreading at basin scale. Five months after its formation, the dense water of coastal origin created a distinct bottom layer up to few hundreds of meters thick over the central part of the NW Mediterranean basin, which was overlaid by a layer of newly formed deep water produced by open-sea convection. These observations highlight the role of intense episodes of both dense shelf water cascading and open-sea convection to the alteration of the characteristics of the NW Mediterranean deep waters.