The Adriatic sea got its name from an ancient port
of the same name. The Adriatic spans from the
Balkan to the Apennine peninsula.
The part belonging to the Republic of Croatia is
the east coast which extends all the way from
Prevlaka in the south to cape Savudrija in the
west, including all islands, islets and cliffs
along the coast, and the archipelago of Palagruza
(the number of islands, beaches, islets and cliffs is more
than 1700). This is a unique area in Europe for
cruising with motor boats, speedboats, or
sailboats, but also for enjoying the underwater
world.
Depths
The shallowest part of our sea is in Istria, where
the depth does not exceed 50 metres. From Pula,
the seabed mildly drops, making a long, narrow
valley which extends from Zirje towards Italy
which is called Jabucka kotlina. The biggest depth
there is about 240 metres. From Jabucka kotlina,
the bottom rises to Palagruza reef where the
biggest depth is 130 metres. Towards the south,
the bottom drops steeply towards the
Juznojadranska dolina, where the biggest measured
depth is about 1,300 metres.
Seabed
The appearance of the underwater relief is the
consequence of tectonic movements, abrasion or
erosion which were active several million years
ago, in times when certain parts of the seabed
were land or the coastal area. Uneven areas on the
bottom are constantly reduced by sedimentation of
detritus from the land. That process is slow, but
constant.
Tides
In the Adriatic, the high and low tides have
relatively small amplitudes. In the southern part,
the difference is rarely above some forty
centimetres, while in the northern part it is
somewhat bigger, so that it comes to 1 metre in
Istria and the Gulf of Trieste. In some narrow
channels and bays, the high tide can grow
considerably during a strong sirocco. That
phenomenon is characteristic for big and deep bays
of the southern Adriatic. The tides are of a mixed
type, which means that their rhythm is semidiurnal
during the new and full moon, and of a daily type
during the first and the last quarter. Their
amplitudes are very irregular.
Sea
Currents
Sea currents occur under the influence of winds,
the difference in pressure, temperature, and the
differences in salinity. With respect to the
direction, they can be horizontal or vertical.
There are also bottom currents which appear as the
consequence of moving of water from warmer areas
to colder ones, during which the surface layer
gets cold and descends towards the seabed.
Currents are weakly observable in the Adriatic.The
speed of currents changes in particular areas, but
it also depends on time periods. The average speed
of currents is about 0.5 knots, but they can also
reach the speed of 4 knots.
Salinity of Sea
The total quantity of salt dissolved in one
kilogram of sea water is called salinity, which is
usually expressed in grams and as the permillage.
The salinity of the Adriatic Sea is 38.30 per mill
averagely, i.e. there is 38.30 g of salt dissolved
in 1 kg of water. In the northern part, the
salinity is somewhat lower than in the middle and
southern part because of the influence of the Po
River.
Sea
Temperature
The Adriatic Sea has a very marked annual change
of the surface temperature. The average annual
temperature is 11°C. During the winter, the sea is
the coldest and the surface temperature is about
7°C; very seldom, it can drop below that too. In
the spring, the sea becomes warmer, and the
surface temperature rises to 18°C. In the summer
the surface of the sea reaches a very high
temperature, of up to 22 to 25°C, and in the
southern Adriatic and Istria up to 27°C. In the
Adriatic, thermoclines, i.e. parts of the water
column of the same temperature, are very well
distinguished. The thermocline is most evident
during the summer, and, in the winter, the
isothermal process arises, i.e. equaling of the
temperature throughout the water column. In the
summer, we can notice the first thermocline at the
depth of 3 to 5 metres, the next one is at about
12 metres, and yet another one at 18 metres, while
below 30 metres the temperature is mostly constant
throughout the year.
Waves in the Adriatic
Waves occur primarily as the consequence of the
blowing of winds. The bigger the reach, i.e. the
surface across which the wind blows, the higher
the waves will be. Their strength depends on the
configuration and the exposure of the coast. In
that way, mixing of the surface layer with water
from the deep is enabled, and the interaction
between the atmosphere and the sea. We distinguish
the crest and the trough of a wave. The length of
the wave is the distance between two troughs. Most
often, heights of waves in the Adriatic are
between 0.5 and 1.5 metres, and they very rarely
exceed 5 metres.
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