Science Mission 1

Bathymetry of the Strait of Sicily
Bathymetry of the Strait of Sicily ©

Flow over sills in the Strait of Sicily

The eastern Mediterranean Sea experiences a large net evaporation of more than 1 metre per year, which causes an exchange flow between the eastern and western basins of the Mediterranean Sea through the Strait of Sicily. Relatively fresh Atlantic water enters the eastern basin through the surface layers and saltier water exits the basin via the deeper layers.

The role of the 'Strait of Sicily’

The Strait of Sicily, which is wide at the surface but with deep water constrained to pass through two narrow gaps in the submarine ridge, plays a crucial role in determining the oceanic climate of the Mediterranean as it is thought that the salinity and temperature of the Mediterranean Sea deep waters are increasing.

Valuable outflow measurements will provide an understanding of the properties of the eastern Mediterranean deep water and an analysis of changes in outflow over time will give much insight into the changes of the large-scale circulation.

Why use Autosub?

The development of Autosub, with terrain following capabilities, provided the opportunity for high-resolution surveys of flow through straits and over sills. The measurements obtained will improve estimates of fluxes and enable a better understanding of measurements obtained from moored instruments.

Autosub’s ability to carry a wide range of instrumentation also provided estimates of the rates of mixing at and downstream of the sill. The results will contribute much to the understanding of these processes.

Related publications

Stansfield K., Smeed D.A., Gasparini G.P., McPhail S., Millard N., Stevenson P., Webb A., Vetrano A. and Rabe B., 2001. Deep-sea, high-resolution, hydrography and current measurements using an autonomous underwater vehicle: The overflow from the Strait of Sicily. Geophysical Research Letters, 28, 2645-2648.

Stansfield K., Gasparini G.P. and Smeed D.A., 2003. High-resolution observations of the path of the overflow from the Sicily Strait. Deep Sea Research Part I: Oceanographic Research Papers, 50(9), 1129-1149.

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