Extreme Western Intermediate Water formation in winter 2010

The Western Intermediate Water (WIW) is probably the less studied water mass in the Western Mediterranean (WMED). It is clearly identifiable as a temperature minimum above the Levantine Intermediate Water (LIW). The WIW circulation from the northern part of the WMED to the south and through the Balearic Channels is well known, but no specific experiments have been devoted to the study of the formation process of this water mass. It is usually accepted, in a vague sense, that WIW is formed in the northern sector of the WMED, in areas surrounding the Gulf of Lions, the Ligurian Sea and the Catalan Sea, being advected towards the Balearic Channels as part of the northern current. The present work shows hydrographic data obtained in late winter in 2010 after severe storms in the WMED. These data show intermediate convective mixing along the whole continental shelf of the Iberian Peninsula, as far to the south as Cape Palos. The data analysed show that, under severe winter conditions, the formation area of WIW is larger than previously thought and the salinity and temperature ranges for this water mass are also wider than those traditionally accepted in the literature. © 2012 Elsevier B.V.