16
V. Barale
can reach up to 20
◦ C, as in the shallow parts of the Adriatic Sea, where the range is
between the 8–10
◦ C of winter and the 26–28
◦ C of summer.
Evaporation greatly exceeds precipitation and river runoff (with an estimated
freshwater deficit of 2,500 km
3 /year), so that the Mediterranean Sea is characterized
by very high salinity (mean around 38 psu), a fact that is central to water circulation
within the basin. Evaporation is especially high in the eastern Mediterranean, causing
the water level to decrease and salinity to increase (up to 39 psu) eastward. The
resulting pressure gradient pushes cooler, lower-salinity (about 36 psu) water from
the Atlantic Ocean across the entire basin. The less dense Atlantic water flows into the
Mediterranean Sea through the Strait of Gibraltar, in the surface layer. The incoming
water
4 warms and becomes saltier as it travels east, and is eventually turned into
denser Mediterranean waters through evaporation. It sinks in the Levantine basin
(as well as in other areas where deep waters are formed), due to winter cooling,
moves back westward and ultimately spills over the sill of the Strait of Gibraltar,
in the bottom layer, and out into the Atlantic Ocean. This distinct Mediterranean
Intermediate Water can be traced in the Atlantic Ocean to the northernmost latitudes,
where it contributes to North Atlantic Deep Water formation. The complete cycle
determines a residence time in the basin of about 80 to 100 years.
Surface circulation is essentially eastward in the southern part of the basin, and
westward along the northern shorelines. In the western basin, the Atlantic Jet moves
from the Strait of Gibraltar to the Sicily Channel, while the current transporting waters
back flows along the Italian, French, and Spanish coasts. Intermittent and long-lived
sub-basin-scale eddies and gyres abound in the Algerian near-coastal region and the
Tyrrhenian Sea. In the eastern basin, surface waters are transported eastward by
several local currents, but recirculate in numerous eddies and gyres before reaching
the northward coastal current off Israel, Lebanon, and Syria and veering westward
off Turkey, in the Levantine Basin.
Deep waters can be formed both in the Adriatic Sea and in the Aegean Sea,
although with different characteristics, and spill out into the eastern basin over the
sills in the Otranto Strait and around Crete, respectively. Deep waters can also be
formed in the Ligurian-Provençal Sea, due to the effect of the Mistral wind, which
increases the density of surface waters through intense evaporation and cooling,
particularly in the Gulf of Lion region. This can lead to a complete overturning of the
water column, with deep convection processes taking place over 2000 m of water.
The process ventilates the deepest parts of the western Mediterranean and triggers the
onset of large algal blooms, sometimes covering the entire northwestern basin. The
deep waters of the eastern and western basins do not communicate, due to the shallow
sill of the Sicily Channel. While a substantial amount of vertical mixing is provided
by strong regional (winter) wind regimes, tidal amplitudes are very small, in the
Mediterranean Sea, and the narrow continental shelves prevent tidal amplification
along the coast.
4 About 1 Sv of transport. The Sverdrup (Sv) is a unit of measure for large oceanic flows: 1 Sv =
10
6 m
3 s
−1 .
V. Barale
can reach up to 20
◦ C, as in the shallow parts of the Adriatic Sea, where the range is
between the 8–10
◦ C of winter and the 26–28
◦ C of summer.
Evaporation greatly exceeds precipitation and river runoff (with an estimated
freshwater deficit of 2,500 km
3 /year), so that the Mediterranean Sea is characterized
by very high salinity (mean around 38 psu), a fact that is central to water circulation
within the basin. Evaporation is especially high in the eastern Mediterranean, causing
the water level to decrease and salinity to increase (up to 39 psu) eastward. The
resulting pressure gradient pushes cooler, lower-salinity (about 36 psu) water from
the Atlantic Ocean across the entire basin. The less dense Atlantic water flows into the
Mediterranean Sea through the Strait of Gibraltar, in the surface layer. The incoming
water
4 warms and becomes saltier as it travels east, and is eventually turned into
denser Mediterranean waters through evaporation. It sinks in the Levantine basin
(as well as in other areas where deep waters are formed), due to winter cooling,
moves back westward and ultimately spills over the sill of the Strait of Gibraltar,
in the bottom layer, and out into the Atlantic Ocean. This distinct Mediterranean
Intermediate Water can be traced in the Atlantic Ocean to the northernmost latitudes,
where it contributes to North Atlantic Deep Water formation. The complete cycle
determines a residence time in the basin of about 80 to 100 years.
Surface circulation is essentially eastward in the southern part of the basin, and
westward along the northern shorelines. In the western basin, the Atlantic Jet moves
from the Strait of Gibraltar to the Sicily Channel, while the current transporting waters
back flows along the Italian, French, and Spanish coasts. Intermittent and long-lived
sub-basin-scale eddies and gyres abound in the Algerian near-coastal region and the
Tyrrhenian Sea. In the eastern basin, surface waters are transported eastward by
several local currents, but recirculate in numerous eddies and gyres before reaching
the northward coastal current off Israel, Lebanon, and Syria and veering westward
off Turkey, in the Levantine Basin.
Deep waters can be formed both in the Adriatic Sea and in the Aegean Sea,
although with different characteristics, and spill out into the eastern basin over the
sills in the Otranto Strait and around Crete, respectively. Deep waters can also be
formed in the Ligurian-Provençal Sea, due to the effect of the Mistral wind, which
increases the density of surface waters through intense evaporation and cooling,
particularly in the Gulf of Lion region. This can lead to a complete overturning of the
water column, with deep convection processes taking place over 2000 m of water.
The process ventilates the deepest parts of the western Mediterranean and triggers the
onset of large algal blooms, sometimes covering the entire northwestern basin. The
deep waters of the eastern and western basins do not communicate, due to the shallow
sill of the Sicily Channel. While a substantial amount of vertical mixing is provided
by strong regional (winter) wind regimes, tidal amplitudes are very small, in the
Mediterranean Sea, and the narrow continental shelves prevent tidal amplification
along the coast.
4 About 1 Sv of transport. The Sverdrup (Sv) is a unit of measure for large oceanic flows: 1 Sv =
10
6 m
3 s
−1 .