The seasonal characteristics of the circulation in the north Mediterranean basin and their relationship with the atmospheric‐climatic conditions

Abstract

The greater heat losses sustained by the Ligurian-Provenqal basin in winter appear to be the major factor leading to the periodic intrusions of the warmer Tyrrhenian water from the east. This is the main conclusion of a 3-year oceanographic investigation carried out in the eastern Ligurian-Provenqal basin in order to monitor the long-term characteristics of its exchanges with the Tyrrhenian Sea. The analysis of the whole data set collected in this period shows that two currents converge north of Corsica after having flowed along the northwestern side of Corsica (the West Corsican Current) and through the Corsican Channel (the Tyrrhenian Current). While the former does maintain nearly steady properties year round, the latter crosses the strait only during the coldest season, thus showing a clear seasonal trend that begins again every year. The comparison with the meteorological parameters of the Ligurian-Provenqal basin indicates that the winter intrusions of the Tyrrhenian current are tightly associated with the heat and water losses through the rise induced in the upper basin density. In addition to reintegrating the heat lost to the atmosphere, the Tyrrhenian flow might also restore the volume of the basin upper layer involved in the deep water formation processes. This enables us to infer that a unique circulation pattern, mostly driven by atmospheric-climatic conditions, involves the northern part of the western Mediterranean Sea.1.

Deep and intermediate water in the western Mediterranean under the influence of the Eastern Mediterranean Transient

“…Some recirculation is also present in the interior of the basin, which leaves the basin through the southern opening [Millot, 1999]. The water exchange through the Corsica Channel involves the whole water column moving nearly always northwards, with a marked seasonal and interannual variability of its transport [Astraldi and Gasparini, 1992].…”

Dispersal strategies of benthic species and water current variability in the Corsica Channel (Western Mediterranean)

“…Time series of current speed and direction show little variability in current direction as suggested by Astraldi and Gasparini (1992); there were stronger fluxes in winter and weaker currents in summer. The current through the Channel was mainly directed toward the northern basin such that the Corsica Channel can be considered as a one-way gate from the Tyrrhenian Sea towards the Ligurian-Provençal basin (Fig.°3).…”

Water fluxes at an ocean margin in the presence of a submarine canyon

“…At the western (upstream) open boundary, the alongshore component of the flow is prescribed to simulate the observed Liguro-Provenc ßal Current, which is based on field measurements off Corsica (Astraldi and Gasparini, 1992). Otherwise, a radiation condition is used at both upstream and downstream open boundaries for all state variables, allowing disturbances originating in the interior of the domain to leave it without disturbing the internal solution (Roed and Cooper, 1987).…”