Dense water generation in the north Adriatic in 1999 and its recirculation along the Jabuka Pit

Abstract

This paper describes thermohaline properties in the north and middle Adriatic Sea in 1999 based on temperature and salinity data collected along the Po-Rovinj, Jabuka Pit and Palagruža Sill profiles. The preconditioning, generation and spread of North Adriatic Dense Water (NAdDW), as well as their relationship to surface fluxes and river discharge are analyzed in detail. A strong Bora wind event in November 1998 resulted in heat loss exceeding 800W/m2, homogenizing and cooling the whole water column by 2.4°C, while another similar Bora episode in January/February with a cooling rate of 1.4°C ended with NAdDW generation. River discharge was low during the preconditioning and generation phases. Following its generation, the NAdDW flowed southeastward as a density current along the western Adriatic slope. Its northeastern part reached the steep edge of the Jabuka Pit and sank rapidly to the bottom, where it was observed a month after its generation. However, the core of the NAdDW current continued to follow the western slope as a density current, taking a detour around the pit on its southeastern side, and sinking to the bottom in the eastern segment of the pit. The detour and sinking at the Jabuka Pit slope was estimated with an analytical model to be 1.1m/km. Finally, the upper lighter part of the NAdDW current crossed the Palagruža Sill and followed the western slope entering the South Adriatic Pit and contributing to the water mass dynamics there. Another NAdDW branch was found at the very bottom of the middle of the Palagruža Sill, although being less pronounced than the one that moved over the western slope.