Observations on a bottom vein of dense water in the southern Adriatic and Ionian seas

Abstract

We discuss the motion and spreading of a bottom vein of very dense marine water, which originates (σ ≥ 29.4) in winter through cooling and evaporation processes resulting from the violet Bora wind blowing over the shallow North Adriatic Sea into the deepest layers of the southern Adriatic and Ionian seas (eastern Mediterranean basin). Our analysis is focused on the peculiar physical processes that control this bottom flow. We first describe the vein motion in the southern Adriatic Sea in which this current follows approximately the isobaths (in partial accordance with the conservation of potential vorticity) and the main mixing process of dense water with Levantine Intermediate Water occurring in an offshore‐oriented canyon near Bari. This canyon causes a deepening and flattening of the original vein of dense water, such that downstream the water can be observed only on the Otranto Sill (at depths of ≈ 800 m with σ ≈ 29.25). The subsequent flow in the Ionian Sea follows approximately the 900‐m isobath in the Gulf of Taranto and along the Calabrian and east Sicilian coasts, in agreement with the results of Smith's and Killworth's theoretical models of steady motion of density driven currents over a regular slope, in a rotating system, for stratified fluids.