Short-term physical and chemical variations in the bottom water of middle Adriatic depressions

Abstract

A physical and chemical dataset collected in the Jabuka (Pomo) depression area (middle Adriatic Sea) was analysed for seasonal and interannual changes in temperature, salinity, density, dissolved oxygen and nitrates. A historical dataset collected from 1980 to 1997 was extended with data from 15 oceanographic cruises conducted between 1998 and 2002 in the framework of the SINAPSI research program. The bottom water masses of the Jabuka pits are periodically renewed by Northern Adriatic Deep Water (NAdDW) at 1 to 3 yr intervals. During late winter-early spring, the new water eventually flows into the western pit and then into the central and eastern ones. During 1 yr of residence in the pits, bottom water nitrates increase 3-fold and dissolved oxygen decreases by 28% due to mineralisation processes. Some aspects of recently observed decadal climatic anomalies in the Northern Adriatic Sea, in particular the average winter sea surface warming, are revealed by the analysed dataset. Relationships were observed between these anomalies and the Eastern Mediterranean Transient (EMT), and from this (and other indirect indications) we infer that since 1999 the Adriatic Sea has re-emerged as a major source of Eastern Mediterranean Deep Water (EMDW). These findings confirm the worth of the mesoadriatic depressions as an easily accessible recording site of interannual oceanographic variations in the Adriatic basin.