HYDRODYNAMICS AND GEOCHEMICAL FLUXES IN THE STRAIT OF OTRANTO
Results of CTD Measurements
The CTD measurements confirmed the presence of four water
masses in the area of the strait, i.e. the Adriatic Surface Water (ASW)
and the Ionian Surface Water (ISW) at the upper layers,
the Levantine Intermediate Water (LIW) from about 150 to 300 m and
the Adriatic Bottom Water (ABW) at the deepest layer.
The THETA/S plot of the
winter cruise
Otranto 1, shows clearly all of them, especially the ASW, which is
the coldest one with a temperature of about 11³C,
and the saltier and warmer ISW, with a temperature of more
than 15³C and a salinity of about 38.25.
During the
summer cruise
Otranto 3, the entire area above
the seasonal thermocline displays rather uniform horizontal temperature
distribution and the distinction between various surface water masses is
mainly due to salinity.
The situations met during winter and summer cruises are
described also by the three-dimensional plots:
the first one
shows a thermal front which extends from the Italian coast
towards East at the first 75 meters, while the
second one
evidences the structure of the LIW, which reaches its maximum salinity at a depth of
about 200 meters.
From the density field the
geostrophic currents at 30 dbar
were computed, taking as the reference level the pressure of 100 dbar,
which is the maximum one common to all stations. As an example,
the figure at right
shows the situation met during the autumn cruise Otranto 3, when the
maximum inflowing gestrophic shear occurred in the wide area along the
eastern side of the strait. This is in a good agreement both with the
results of some previous studies and with our current measurement data.
Paolo Scarazzato
e-mail : spaolo@ogs.trieste.it