Atmospheric data from reanalysis, satellite, and experimental observations have been combined to calculate a four‐year time series of the Atlantic inflow through the Strait of Gibraltar. The net flow through the strait, estimated from the Mediterranean water budget, and the Mediterranean outflow, estimated from currentmeter observations in Espartel sill (western Strait of Gibraltar) from October 2004 to January 2009, made it possible to estimate the Atlantic inflow as the sum of both of them. The obtained mean net flow is 0.038 ± 0.007 Sv, with a seasonal cycle of 0.042 ± 0.018 Sv annual amplitude and maximum in September. The Mediterranean outflow shows a seasonal signal with annual amplitude of 0.027 ± 0.015 Sv peaking in April (in absolute value), and a mean value of −0.78 ± 0.05 Sv. The resulting Atlantic inflow has a mean value of 0.81 ± 0.06 Sv and a seasonal cycle with annual amplitude of 0.034 ± 0.011 Sv, peaking in September, and high interannual variability. The inflow seasonal cycle is the result of a barotropic forcing associated with the cycle of the net flow, driven by the evaporative cycle, and a baroclinic forcing linked to the seasonal cycle of the reduced gravity that drives the exchange.

Several NCEP climatological datasets have been combined to analyse the seasonal and interannual variations of the heat and water budgets in the Mediterranean Sea, and compare the long‐term means with direct measurements in the Strait of Gibraltar. The seasonal cycle of the net heat is positive (toward the ocean) between March and September with maximum in June and negative the rest of the year with minimum in December. Although subject to inherent uncertainty, we obtain a practically neutral budget of 0.7 Wm⁻² in a yearly basis. The net heat budget is positive for the western Mediterranean (∼12 Wm⁻²) and negative for the eastern Mediterranean (∼− 6.4 Wm⁻²) mainly due to the high latent heat losses of this basin. The evaporation minus precipitation (E–P) freshwater deficit has a seasonal cycle with a range of variation about 600 mm·y⁻¹, maximum in August–September and minimum in May. The long‐term mean of the basin‐averaged deficit is 680 ± 70 mm·y⁻¹ but it is almost 70% greater in the eastern Mediterranean due to higher E and lower P in this basin. Combining the climatological values with in situ measurements in Espartel sill, a mean inflow through the Strait of Gibraltar of 0.82 ± 0.05 Sv is obtained and a salinity ratio S_in/S_out = 0.956. A heat advection Q_a = 3.2 ± 1.5 Wm⁻² through the Strait of Gibraltar has been obtained that, combined with the long‐term averaged surface heat flux, implies that the net heat content of the Mediterranean Sea would have increased in the last decades. Copyright © 2010 Royal Meteorological Society