Mass transport between a semienclosed basin and the ocean: Maracaibo System

Field data and three-dimensional numerical (Estuary and Lake Computer Model) simulations are used to investigate exchange between Lake Maracaibo and the Gulf of Venezuela. This exchange occurs along a dredged shipping lane 100 km long and 14 m deep. It is driven by a density difference between the lake and gulf and modulated at tidal and subtidal timescales by water level fluctuations in the gulf propagating to the lake. At tidal frequencies, exchange is modulated by barotropic forcing and nonlinear baroclinic response, leading to a severance of high-salinity bottom water into seaward and landward segments. Bottom water in the landward segment is moved lakeward along the shipping lane, where it is mixed vertically and flushed out. Subtidal water level fluctuations in the gulf force barotropic currents along the shipping lane, dominating variability of volume and salt flux at timescales of 1-4 weeks. The barotropic component of simulated salt flux decreases from the gulf to the lake, as depth-averaged salinity decreases, while simulated baroclinic exchange is only 20% of that predicted by quasi-steady two-layer hydraulic theory. These reductions in salt flux are due to intense mixing that occurs throughout the shipping lane.