The Mediterranean Sea shows a peculiar anomaly in its nutrient pattern compared to the global ocean, as there is decrease in nutrient concentration from west to east. This feature has been attributed to the antiestuarine circulation at the Strait of Gibraltar, where an eastward flow of Atlantic nutrient‐poor surface waters is compensated by a westward countercurrent of Mediterranean nutrient‐rich deep waters. This water exchange has been suggested as the ultimate cause for the oligotrophy of the Mediterranean basin, even though only a few studies have accurately examined the magnitude of the nutrient flux through the Strait of Gibraltar. In this work, data from the Gibraltar Fixed Time series (GIFT) between 2005 and 2008 were used to assess nutrient distributions. Applying a two‐layer model of water mass exchange and using the Mediterranean outflow recorded in situ, the net export of nutrients from the Mediterranean to the Atlantic was calculated as 139 and 4.8 Gmol yr⁻¹ of nitrate and phosphate, respectively. The results also demonstrated that the Atlantic inflow is not nutrient depleted and in particular contains significant levels of phosphate, which is the limiting factor for biological productivity in the eastern Mediterranean. The distribution of the quasi‐conservative parameter N* in the western and eastern basins indicated that nitrate‐deficient surface waters are transformed into phosphate‐deficient bottom waters by internal cycling processes. Therefore, phosphate depletion in the Mediterranean does not have its origin in the entry of a phosphorus‐impoverished Atlantic inflow through the Strait of Gibraltar.

The exchange of both anthropogenic and natural inorganic carbon between the Atlantic Ocean and the Mediterranean Sea through Strait of Gibraltar was studied for a period of two years under the frame of the CARBOOCEAN project. A comprehensive sampling program was conducted, which was design to collect samples at eight fixed stations located in the Strait in successive cruises periodically distributed through the year in order to ensure a good spatial and temporal coverage. As a result of this monitoring, a time series namely GIFT (GIbraltar Fixed Time series) has been established, allowing the generation of an extensive data set of the carbon system parameters in the area. Data acquired during the development of nine campaigns were analyzed in this work. Total inorganic carbon concentration (C_T) was calculated from alkalinity-pH_T pairs and appropriate thermodynamic relationships, with the concentration of anthropogenic carbon (C_ANT) being also computed using two methods, the ΔC* and the TrOCA approach. Applying a two-layer model of water mass exchange through the Strait and using a value of −0.85 Sv for the average transport of the outflowing Mediterranean water recorded in situ during the considered period, a net export of inorganic carbon from the Mediterranean Sea to the Atlantic was obtained, which amounted to 25±0.6 Tg C yr⁻¹. A net alkalinity output of 16±0.6 Tg C yr⁻¹ was also observed to occur through the Strait. In contrast, the Atlantic water was found to contain a higher concentration of anthropogenic carbon than the Mediterranean water, resulting in a net flux of C_ANT towards the Mediterranean basin of 4.20±0.04 Tg C yr⁻¹ by using the ΔC* method, which constituted the most adequate approach for this environment. A carbon balance in the Mediterranean was assessed and fluxes through the Strait are discussed in relation to the highly diverse estimates available in the literature for the area and the different approaches considered for C_ANT estimation. This work unequivocally confirms the relevant role of the Strait of Gibraltar as a controlling point for the biogeochemical exchanges occurring between the Mediterranean Sea and the Atlantic Ocean and emphasizes the influence of the Mediterranean basin in the carbon inventories of the North Atlantic.

L'écosystème pélagique de la côte atlantique marocaine est influencé par la variabilité spatio-temporelle de l' upwelling . L'évolution des paramètres physico-chimiques et biologiques ainsi que leur corrélation et leur regroupement par l'analyse en composante principale nous ont permis de subdiviser le littoral atlantique en quatre zones de remontées : deux zones situées au nord de Cap Juby (28°N), caractérisées par une activité estivale et deux zones situées au sud, actives en permanence avec une intensité variable.

We use a combination of satellite, in situ, and numerical data to provide a comprehensive view of the seasonal coastal upwelling cycle off NW Africa in terms of both wind forcing and sea surface temperature (SST) response. Wind forcing is expressed in terms of both instantaneous (local) and time‐integrated (nonlocal) indices, and the ocean response is expressed as the SST difference between coastal and offshore waters. The classical local index, the cross‐shore Ekman transport, reproduces reasonably well the time‐latitude distribution of SST differences but with significant time lags at latitudes higher than Cape Blanc. Two nonlocal indices are examined. One of them, a cumulative index calculated as the backward averaged Ekman transport that provides the highest correlation with SST differences, reproduces well the timing of the SST differences at all latitudes (except near Cape Blanc). The corresponding time lags are close to zero south of Cape Blanc and range between 2 and 4 months at latitudes between Cape Blanc and the southern Gulf of Cadiz. The results are interpreted based on calculations of spatial and temporal auto and cross correlations for wind forcing and SST differences. At temporal scales of 2–3 weeks, the alongshore advection of alongshore momentum compensates for interfacial friction, allowing the upwelling jet and associated frontal system to remain active. We conclude that the coastal jet plays a key role in maintaining the structure of coastal upwelling, even at times of relaxed winds, by introducing a seasonal memory to the system in accordance with the atmospheric‐forcing annual cycle.

This study describes some physical oceanography features of an estuary maintained by fresh groundwater inflow. The mesoscale variability of currents, temperature and salinity are documented from moored current meter observations of 12 days duration at three stations. Current speeds exceeded 0.7m.s−1 during spring tides and decrease to 0.1m.s−1 during neap tides. Current directions followed the major channel axes, reversing by 180 degrees between the flood and the ebb tides. Harmonic analysis indicated that tidal currents were mainly semi-diurnal, with a predominance of the M2 harmonic, but included M4 and M6 sub-harmonics, possibly resulting from non-linear interactions of the flow with the shallow bottom and channel curvatures. Close to the lagoon entrance the water is of marine character but, further upstream, salinity decreased significantly. In the absence of river runoff, this decrease must result from some yet undisclosed underground freshwater inflow. The water renewal time estimated using the tida...