Observations of a vein of very dense marine water in the southern Adriatic Sea

Abstract

A bottom vein of dense water has been observed in the course of hydrological measurements carried out in three different periods—November 1980, February 1981 and June 1983—on the southern boundary of the shelf of the Adriatic Sea. The basin is renowned for cold, dense marine water generated in its northern portion by the Bora. Characteristic values of temperature, salinity and density of the central part of this vein of dense water are as follows: T ⋍ 13.70°C, S ⋍ 38.65‰ and σ 1 ⋍ 29.09 in November 1980; T ⋍ 12.4°C, S ⋍ 38.6‰, σ 1 ⋍ 29.3 in February 1981; and T ⋍ 12.52°C, S ⋍ 38.47‰ and σ 1 ⋍ 29.00 in June 1983. This water flows into the Southern Adriatic Trough, where it mixes with the Levantine type water. It follows the Italian shelf break at a depth of 100–300 m, gradually deepening until it reaches S. Maria di Leuca. The resulting water flows into the Ionian Sea through the Otranto Channel (740 m deep). An early hypothesis of Pollak is that this mixed water provides the main source of the abyssal water of the eastern Mediterranean Sea. A theoretical analysis, based on the classical steady model of Smith and a recent study by Shaw and Csanady, has allowed the fluxes to be estimated as 0.6–0.8 10 5 m 3 s −1 at the moment of maximum flux.