Geodynamical processes in the channel connecting the two lobes of the Large Aral Sea

摘要

Reasons for the existence of the channel connecting the two lobes of thepresent Large Aral Sea are discussed. In situ measurements in 2005 show thatdifferences between the measured depths and those contained in the availabledigital bathymetry of the lake are considerably different at the channel(7.5±0.9 m, at nine measurement stations along it) and at the northernpart of the eastern lobe (1.6±0.3 m, at six stations from the westernto the eastern shore). Differences in the misfits observed in the two zonesare discussed and thought to be a consequence of the variation of thetransversal area of the channel as it enters the eastern lobe, which wouldaffect the flow velocity and thus the strength of the erosion process at thebottom. Field data together with satellite images have been used to modifyan original digital bathymetry of the lake and have been implemented into a3-D hydrodynamical model. A numerical simulation shows that a wind of 12 m/sblowing from the east (112°) generates velocities of up to 45 cm/s inthe channel, allowing denser water from the eastern lobe (salinity: 132 g/kg)to flow about 38 km towards the fresher western lobe (salinity: 98 g/kg)in one day. The effect of the inflow on the vertical structure of thewestern lobe is also illustrated. Although nowadays the channel will be soona thing of the past, in a more general context, the Aral Sea is presented asan example showing that geomorphologic and geophysical processes, along withhydrological and atmospheric processes, must be taken into account forshort-term predictions.