372
LM. Munda
Trieste there are only two depressions at the capes of Strunjan and Punta
Madonna near Piran (Orozen-Adamic 1981).
The bottom topography of the northern Adriatic was determined by
several pre- and postglacial events. The sea bottom in the Gulf of Trieste
is mostly Paleocene flysch, while Cretaceous limestone prevails farther
south along the Istrain coast. Alluvial Holocene sediments are usual
below about 10 m depth in both areas mentioned above (Meischner
1973).
The bottom topography is responsible for the course of the main
currents in the Adriatic as a whole (Zore-Armanda 1968). In the northern Adriatic, a regular circular convection current transfers river-borne
and urban pollutants in the surface water layers. Local circuits of a
changing direction were noticed in the Gulf of Trieste (Rajer 1990),
prop ably responsible for the transport of pollutants during calm weather.
In addition, there is, however, a cyclonic circulation over the Adriatic as
a whole. In the northernmost shelf area the surface water is under the
impact of freshwater runoff from the north Italian rivers, while the open
northern Adriatic is influenced by advection from the south. Long-term
collected hydrographic data have revealed the existence of a frontal zone
between colder, low-salinity water from the north and the saltier, warm
water from the south (Zore-Armanda et al. 1983). The position of this
semi-permanent frontal zone is influenced by the "bora" winds, which
blow in an offshore direction. In the northernmost part of the Adriatic
the Po river affects the formation of a peculiar circulation. A line
between the Po river mouth and Rovinj separates two gyres, an anticyclonic south and a cyclonic north of this line (Zore-Armanda and Vucak
1984). The response of this current field to the "bora" wind has been
examined by current data analyses (Mosetti 1972; Zore-Armanda and
GaCic 1987). The influence of the Po river, which carries a heavy load of
pollutants, is, however, most pronounced during the "bora" wind and
during summer stratification (Marchetti et al. 1989).
Temperature and salinity data were collected by us in the investigated
area at Piran in the Gulf of Trieste (Table 16.1). Measurements were
carried out at the surface and at 1,3, and 7 m depths.
In February/March the water temperature was at its minimum and
increased with depth. The opposite trend was noticed in April while
homeothermic conditions were indicated in May and October. During
summer stratification, the water temperature decreased with depth,
whereas in November the opposite trend was observed. Seasonal variations of salinity were opposite to those of the water temperature, i.e.
minima in June/July and maxima in February/March. Except for August,
there was a tendency of salinity increase with depth.
LM. Munda
Trieste there are only two depressions at the capes of Strunjan and Punta
Madonna near Piran (Orozen-Adamic 1981).
The bottom topography of the northern Adriatic was determined by
several pre- and postglacial events. The sea bottom in the Gulf of Trieste
is mostly Paleocene flysch, while Cretaceous limestone prevails farther
south along the Istrain coast. Alluvial Holocene sediments are usual
below about 10 m depth in both areas mentioned above (Meischner
1973).
The bottom topography is responsible for the course of the main
currents in the Adriatic as a whole (Zore-Armanda 1968). In the northern Adriatic, a regular circular convection current transfers river-borne
and urban pollutants in the surface water layers. Local circuits of a
changing direction were noticed in the Gulf of Trieste (Rajer 1990),
prop ably responsible for the transport of pollutants during calm weather.
In addition, there is, however, a cyclonic circulation over the Adriatic as
a whole. In the northernmost shelf area the surface water is under the
impact of freshwater runoff from the north Italian rivers, while the open
northern Adriatic is influenced by advection from the south. Long-term
collected hydrographic data have revealed the existence of a frontal zone
between colder, low-salinity water from the north and the saltier, warm
water from the south (Zore-Armanda et al. 1983). The position of this
semi-permanent frontal zone is influenced by the "bora" winds, which
blow in an offshore direction. In the northernmost part of the Adriatic
the Po river affects the formation of a peculiar circulation. A line
between the Po river mouth and Rovinj separates two gyres, an anticyclonic south and a cyclonic north of this line (Zore-Armanda and Vucak
1984). The response of this current field to the "bora" wind has been
examined by current data analyses (Mosetti 1972; Zore-Armanda and
GaCic 1987). The influence of the Po river, which carries a heavy load of
pollutants, is, however, most pronounced during the "bora" wind and
during summer stratification (Marchetti et al. 1989).
Temperature and salinity data were collected by us in the investigated
area at Piran in the Gulf of Trieste (Table 16.1). Measurements were
carried out at the surface and at 1,3, and 7 m depths.
In February/March the water temperature was at its minimum and
increased with depth. The opposite trend was noticed in April while
homeothermic conditions were indicated in May and October. During
summer stratification, the water temperature decreased with depth,
whereas in November the opposite trend was observed. Seasonal variations of salinity were opposite to those of the water temperature, i.e.
minima in June/July and maxima in February/March. Except for August,
there was a tendency of salinity increase with depth.