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The line marked by * indicates the potential density for the final product after mixing (Price and Baringer, 1994). Afff is the density decline due to mixing.

Fig. 5.13 Difference in the in situ density between the Mediterranean outflow and the other three sources of deep water, in kg/m3.

salinity AS = 1.83 or a decline in temperature AT = -4.82°C can produce a water mass that is the densest among all four sites of deepwater formation, so that the Mediterranean outflow would flow to the bottom of the world's oceans (Table 5.2).

This calculation does not include the effect of mixing. Were the effect of mixing taken into the consideration, the change in either the temperature or salinity required to make

Salinity along 18.5oW

Salinity along 18.5oW

Fig. 5.14 Salinity distribution at 18.5° W in the Atlantic Ocean.

the water dense enough to sink to the bottom would be even larger. During the geological past, the evaporation rate over the Mediterranean Sea might have been much higher than the present day. Whether such a possibility could occur under such circumstances remains unclear.

Dynamics of overflows

Overflow from a marginal sea to the open ocean can be described in two steps (Fig. 5.16) (Price and Yang, 1998). First, the mass flux over the sill, a relatively narrow gap, is controlled by hydraulic processes. Second, the gravity current moves downstream from the sill.

The flow through the control section is regulated by the following constraints on mass fluxes, temperature and salinity:

where Min and Mout are the mass flux in and out of the marginal sea, E - P is the rate of evaporation minus precipitation (including river run-off), Pf is the density of freshwater associated with evaporation and precipitation, A is the area of the marginal sea, Tin, Tout, Sin,

Table 5.2. Density difference between the Mediterranean outflow and other sites of deepwater formation, assuming changes in the deepwater properties of the Mediterranean outflow

Depth Denmark Faroe Bank Filchner Ice

Table 5.2. Density difference between the Mediterranean outflow and other sites of deepwater formation, assuming changes in the deepwater properties of the Mediterranean outflow

Depth Denmark Faroe Bank Filchner Ice

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