342 Nadia Pinardi et al.
17.2 The Mediterranean Sea shelf and coastal ecosystems
The shelf areas of the Mediterranean Sea are depicted in Fig. 17.1, limited by the
200-m. isobath contour. They involve narrow coastal strips in the majority of the
cases but some extended shelves are also present. In the Northem part, the
extended she1f areas are adjacent to the river deltas such as the Ebro, the Rhone, the
Po and the Neretva to mention only the major rivers. In addition to that, the Northem Aegean Sea has an extended shelf area partially forced by the low salinity
water inflow from the Dardanelles and other local rivers. an the Southem part, the
extended shelf areas consist of the Nile delta region and the Tunisian she1f on the
Sicilian plateau.
The remaining basin regions are deep ocean areas with steep continental slopes.
The abyssal basins can reach depths of 3500 m over extended areas. The Mediterranean Sea is considered by enlarge a deep ocean basin containing analogues of
deep ocean circulation processes such as deep open ocean formation and meridional thermohaline overtuming. Such deep, open ocean circulation is influencing
the shelf/coastal circulation and its primary productivity especially when the slope
is steep as in general is for the Mediterranean case (Csanady, 1982).
The winter average surf ace circulation produced by the general circulation model
which will be described few sections later, is shown in Fig. 17.2a. In the same picture the winter average surf ace chlorophylI map from a satellite sensor in the visibIe range is also shown (Sea-viewing Wide Fie1d-of-view Sensor, SeaWiFS, http://
seawifs.gsfc.nasa.gov/SEAWIFS.html). First of alI, the circulation is composed of
intensified free and boundary currents and sub-basin scale gyres, both cyclonic and
anticyclonic (Pinardi and Masetti, 2000). These circulation structures impinge on
the narrow shelf areas partially driving the shelf flow field. Thus the shelf area circulation is connected to remote forcing such as the Gibraltar Strait inflow, the center of the basin wind vorticity input (Molcard et al., 2001) and deep/intermediate
water formation processes (Nittis and Lascaratos, 1998, Haines and Wu, 1998).
The ecosystem response at the level of primary producers is large on the
extended shelf areas, in correspondence with the major river estuaries and deltas,
along the Northem and Southem coasts. However, the large scale flow field forces
the ecosystem response inducing biomass horizontal transport, vertical upwelling
of nutrients and determining the depth of the nutricline, associated with the seasonal thermocline formation. The influence of the large scale geostrophic flow
field can be seen in the Gulf of Lyon Gyre area of Fig. l7.2b, where a relative maximum in Chlorophyll is reached around the border of the gyre. The negative zonal
gradient between Westem and Eastem Mediterranean basins is connected to the
Atlantic water influence. The positive meridional gradient across the basin is sustained by isopycnal slopes in the first 100-200 meters favoring northem upwelling
of nutrient rich waters and downwelling in the Southem regions and the presence
ofrivers in the Northem shelves (Crise et al., 1998).
Thus the overall basin primary productivity is dominated by the contribution of
river inflow in the shelf areas and by the large-scale upwelling/downwelling circu-
17.2 The Mediterranean Sea shelf and coastal ecosystems
The shelf areas of the Mediterranean Sea are depicted in Fig. 17.1, limited by the
200-m. isobath contour. They involve narrow coastal strips in the majority of the
cases but some extended shelves are also present. In the Northem part, the
extended she1f areas are adjacent to the river deltas such as the Ebro, the Rhone, the
Po and the Neretva to mention only the major rivers. In addition to that, the Northem Aegean Sea has an extended shelf area partially forced by the low salinity
water inflow from the Dardanelles and other local rivers. an the Southem part, the
extended shelf areas consist of the Nile delta region and the Tunisian she1f on the
Sicilian plateau.
The remaining basin regions are deep ocean areas with steep continental slopes.
The abyssal basins can reach depths of 3500 m over extended areas. The Mediterranean Sea is considered by enlarge a deep ocean basin containing analogues of
deep ocean circulation processes such as deep open ocean formation and meridional thermohaline overtuming. Such deep, open ocean circulation is influencing
the shelf/coastal circulation and its primary productivity especially when the slope
is steep as in general is for the Mediterranean case (Csanady, 1982).
The winter average surf ace circulation produced by the general circulation model
which will be described few sections later, is shown in Fig. 17.2a. In the same picture the winter average surf ace chlorophylI map from a satellite sensor in the visibIe range is also shown (Sea-viewing Wide Fie1d-of-view Sensor, SeaWiFS, http://
seawifs.gsfc.nasa.gov/SEAWIFS.html). First of alI, the circulation is composed of
intensified free and boundary currents and sub-basin scale gyres, both cyclonic and
anticyclonic (Pinardi and Masetti, 2000). These circulation structures impinge on
the narrow shelf areas partially driving the shelf flow field. Thus the shelf area circulation is connected to remote forcing such as the Gibraltar Strait inflow, the center of the basin wind vorticity input (Molcard et al., 2001) and deep/intermediate
water formation processes (Nittis and Lascaratos, 1998, Haines and Wu, 1998).
The ecosystem response at the level of primary producers is large on the
extended shelf areas, in correspondence with the major river estuaries and deltas,
along the Northem and Southem coasts. However, the large scale flow field forces
the ecosystem response inducing biomass horizontal transport, vertical upwelling
of nutrients and determining the depth of the nutricline, associated with the seasonal thermocline formation. The influence of the large scale geostrophic flow
field can be seen in the Gulf of Lyon Gyre area of Fig. l7.2b, where a relative maximum in Chlorophyll is reached around the border of the gyre. The negative zonal
gradient between Westem and Eastem Mediterranean basins is connected to the
Atlantic water influence. The positive meridional gradient across the basin is sustained by isopycnal slopes in the first 100-200 meters favoring northem upwelling
of nutrient rich waters and downwelling in the Southem regions and the presence
ofrivers in the Northem shelves (Crise et al., 1998).
Thus the overall basin primary productivity is dominated by the contribution of
river inflow in the shelf areas and by the large-scale upwelling/downwelling circu-