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evaporation processes and then it spreads westward at an intermediate depth, penetrating
over the Central Mediterranean ridge and eventually entering the western basin after
crossing the Strait of Sicily. The LIW has a higher velocity due to the Bernoulli effect: LIW
has a narrow area to flow in comparison the wide area available to MAWs consequence, it
enables the upper layer of the Eastern Mediterranean Deep Water (EMDW) in the Ionian sea
to reach the western basin (Astraldi et al 2001; Gasparini et al., 2005).

The core of the Levantine Intermediate water is indicated by a maximum at a depth of about
300 meters with a temperature of 13.75 - 13.92°C and a salinity of 38.73 - 38.78 psu at the
channel. The Levantine Intermediate water has maximum salinity in the western and
southwestern approaches of Malta. The renewal time of the total Levantine water in the strait
is estimated to be 9 months, long enough to maintain a fairly constant salinity over the
annual cycle. This also indicates that the characteristics of the Levantine Intermediate water
incident into the strait from the eastern Mediterranean are also quite stable.
Upwelling along the eastern and southern costs of Sicily is a permanent feature. As
explained by Beranger et al., (2004), upwelling is governed by the south-eastward winds and
by the inertia of the isopycnal domes of the AIS meanders and cyclonic vortices that can
extend its influence far offshore due to the configuration of the circulation.
Many eddies of variable strength, shape and size (cyclonic and anticyclonic) are noticed in
the Tunisian–Sicily region. According to Savini et al (2009) between Adventure Bank and the
Malta plateau, LIW forms a pair of subsurface eddies (one cyclonic, one anticyclonic) along
the western flank of the Malta plateau and AIS forms a cyclonic vortex off Cape Passero. The
flux of LIW is not constant but subject to a seasonal variability and calculated to be 2–3 times
higher in winter with respect to summer. The thickness of the LIW layer changes
substantially with the seasons, wider in fall-winter and thicker in spring-summer.

3.3 Eastern Mediterranean Deep Water (EMDW)

The deeper Eastern Overflow Water (EOW) represents the water incident from the eastern
Mediterranean overflowing over the south–central Mediterranean ridge into the Tyrrhenian
Sea. It consists of LIW and Eastern Mediterranean Deep Water (EMDW), which is colder and
fresher than the LIW. Below the LIW there is a significant volume of transient EMDW
(tEMDW). In the Straits of Sicily area the tEMDW appears as a colder and fresher water
mass with respect to the LIW, having a core characterised by a minimum temperature of
13.63°C and a salinity of 38.73.

The topography mainly shapes the intermediate and bottom circulations, which show almost,
stable situations. The spreading westward water masses constitute an undercurrent which,
spilling over the sills of the Straits of Sicily, partially compensates the transport of the upper
flow and bring salty and warm waters into the Western Mediterranean.

The horizontal distribution of these multiple water masses gives evidence to the strong

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