The entrainment decreases with increasing steepness of the bottom and R. In addition, the dependence of both entrainment and mixing on the parameters varied is discussed. The entrainment is found to depend on both Froude, Fr, and Reynolds, Re, numbers. Entrainment and mixing in a lock-release gravity current are studied using different entrainment parameters and an energy budget method. The numerical results are compared with laboratory experiments and a good agreement is found. Relevant parameters, such as the aspect ratio of the initial volume of dense fluid in the lock R, the angle between the bottom boundary and the horizontal direction θ and the depth aspect ratio ϕ, are varied. Lock-exchange gravity currents propagating up a slope are investigated by large eddy simulations, focusing on the entrainment and mixing processes occurring between the dense current and the ambient fluid.
In this way, the space-time behaviour of a signal linked to a climatic event could thus be experimentally evidenced and studied. From our observations the impact created by them in the Tyrrhenian Sea was also observed. In particular, from a nearly annual observations we could observe the effects produced in the Sicily Strait by the water masses produced by the climatic transient occurred in the Eastern Mediterranean from its origin in the late '80s to the present phase of relaxation. A long-term monitoring of the hydrographic properties of water masses across this strait initiated in the second half of the '80s allowed us to evidence the principal time scales of the water exchange between the Ionian Sea and the Tyrrhenian Sea. In this scenario an important role is played by the Sicily Strait dividing the two principal sub-basins: the Eastern and the Western Mediterranean. We may also consider that the distinct sub-basins, often subjected to different atmospheric and dynamic regimes, produce specific water masses that can reach all the Mediterranean regions as far as the adjacent Atlantic Ocean by the connecting network provided by the internal straits and channel.
The rapid response of this basin when compared with the ocean time scales, makes the interannual variability of the circulation an important signal that, in some regions, may prevail on the annual cycle. Recent studies have definitively evidenced the highly sensitivity of the Mediterranean to the effects produced by the large-scale atmospheric systems.
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