Meteorologically forced subinertial flows through the Strait of Gibraltar

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Abstract
The observed transport due to subinertial flows, with periods ranging from days to a few months, through the Strait of Gibraltar reaches values up to 106 m3 s−1, and is well correlated with atmospheric pressure fluctuations over the Mediterranean Sea. This transport is barotropic and accounts for 84% of the variance observed at these frequencies. A second mode accounts for 12% of the variance and is characterized by a node (zero amplitude) located at the mean depth of the interface between Atlantic and Mediterranean waters. This baroclinic mode is modulated by the spring‐neap tidal cycle, corresponding to an increased exchange of waters between Atlantic and Mediterranean at neap tides. A simple model of the Mediterranean, which includes two basins and two straits, indicates that the system has two resonant frequencies at periods of 1.2 and 5.6 days. The 1.2‐day resonance corresponds to the eastern and western basins oscillating through the Strait of Sicily, while that at 5.6 days is the resonance of the Mediterranean Sea with the North Atlantic Ocean. A good approximation to the observed flows is obtained when this model is forced with the most energetic mode of the atmospheric pressure over the eastern and the western Mediterranean and a friction term is included to limit the flow through the Strait of Gibraltar. Restricting the flow through the Strait of Sicily does not improve the agreement between the model and the observations for the flows at Gibraltar.

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