The role that the Algeciras Bay, a medium size embayment located in the eastern part of the Strait
of Gibraltar, may have on the water exchange through the Strait and on other physical properties of
the area has been numerically investigated using different configurations of a numerical model. Three
domains have been considered, the present configuration with the Bay and two other configurations
in which the Bay is suppressed either by filling the embayment, which produces a longer Strait, or by
removing the Gibraltar Rock and isthmus, which gives rise to a shorter Strait. Only little modifications
are produced in the mean properties, the shorter Strait increasing very slightly the mean exchange and
diminishing the cross-section averaged salinity of the inflow. The spatial pattern of semidiurnal tidal
ellipses is changed in the vicinity of the Bay, but other properties such as the minimum amplitude of
semidiurnal M2 transport that occurs off the Bay in the Strait and that could be related to the present
configuration, remain unaltered. It is speculated that the main consequence of suppressing the Bay
relates to the export of primary production, as it acts out as a buffer of water with residence times
long enough to sustain high levels of productivity.
