Abstract

Annual budgets of salinity, total inorganic carbon, total alkalinity, nitrates, phosphates and silicates are estimated through the Strait of Bab-el-Mandab. Two different methods that decouple the summer and winter periods are used. A direct method uses the concentrations of these parameters, the velocity of currents, and the area of a cross section in the strait. The calculations for the fluxes and budgets during the summer period were based on data collected during two cruises made in July and September 1982 (MEROU 1 and 2). An indirect method, based upon matrix inversion and the assumption of a steady-state balance of several properties over a period of one year, is used to calculate the winter and summer budgets of water, salinity, total inorganic carbon, total alkalinity, nitrates and phosphates. The summer budgets obtained by the two different methods are positive for all the properties—a gain for the Red Sea—and are of the same order of magnitude for both methods. For the winter period, budgets are positive for total inorganic carbon and total alkalinity and negative for salinity and nutrients. This gain of total inorganic carbon and total alkalinity through the Strait of Bab-el-Mandab can be quantitatively explained by exchanges of CO2 with the atmosphere and the processes of sedimentation in the basin.

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