Direct estimate of water, heat, and salt transport through the Strait of Otranto

The transport of water volume, salt and heat was calculated using continuous measurements of currents in the Otranto Strait for a one-year period in 1994-95. Temperature and salinity data sets, available from five hydrographic surveys, were used to obtain the seasonal temperature and salinity distributions at the Otranto transect. The Variational Inverse Method (VIM) was applied to reconstruct spatial distributions of the de-tided low-pass inflowing current component, salinity and temperature. Errors associated with estimates of transports are influenced by the data coverage: the higher the spatial resolution, the smaller the error and vice versa. Volume transport reaches a maximum in winter and spring and attains its minimum in summer. The obtained volume transport [similar to 1 Sv (10(6) m(3)s(-1))] should be considered a lower limit value since in that period the Adriatic was producing relatively small quantities of deep water due to the inflow of low-salinity (high buoyancy) waters and relatively mild winters. Comparing the mean advective heat input and the air-sea heat loss, the same order of magnitude between the two has been obtained which is satisfactory considering the possible errors of the two approaches. The relative importance of the eddy heat transport to the total transport is estimated to be only about 5% and thus it can be neglected in a first approximation. The salt transport estimates show a net input, suggesting a salinity increase during the period of study; this was confirmed from the long-term salinity data in the Southern Adriatic.