Upper thermal structure and intermediate currents in the Adriatic and Northern Ionian as measured by a Lagrangian profiler in 1995 and 1996

A Profiling Autonomous Lagrangian Circulation Explorer (PALACE) was deployed twice in the Strait of Otranto (entrance of the Adriatic Sea) to measure intermediate currents and temperature profiles in the upper water column. The profiling instrument was programmed to stay immersed and drift at a neutral depth near 350 dbar for about 51 hours and then to float at the surface for about 21 hours in order to be located by, and relay data to, the Argos satellite system. Temperature data were collected during each ascent between 333 dbar and the surface with 3 dbar vertical resolution. The PALACE was first deployed on 18 May 1995 and was subsequently recovered in the northern Ionian Sea on 26 August 1996. After maintenance, the same float was redeployed at the same location in the Strait of Otranto in November 1995 and provided data in the Adriatic Sea until December 1996. Displacements at intermediate depths indicated that the typical mean speed at the float neutral depth is 5 cm/s, which is about four times smaller than the mean speeds of surface drifters in the same region. Over one hundred temperature profiles were acquired. The temperature profiles measured by the PALACE delineate clearly the seasonal development of the thermocline and upper mixed layer, with the former reaching a maximum depth near 50 m in late summer and fall. Superimposed on this seasonal trend, temperature variations at shorter time scales (5-10 days) can be seen. These variations are mostly related to mesoscale spatial structures observed in the float track and in satellite thermal images.