Abstract. The present study investigates the deep gravity current between the
middle and southern Caspian Sea basins caused by the density difference of
deep waters. Oceanographic data, a numerical model and a dynamic model are
used to consider the structure of this Caspian Sea abyssal overflow. The CTD
data are obtained from UNESCO, and the three-dimensional COHERENS ocean model
results are used to study the abyssal currents in the southern basin of the
Caspian Sea. The deep overflow is driven by the density difference, which is mainly owing to the
temperature difference, between the middle and southern basins, especially in
winter. Due to cold weather in the northern basin, water sinks at high
latitudes and after filling the middle basin it overflows into the southern
basin. As the current passes through the Absheron Strait (or sill), we use
the analytic model of Falcini and Salusti (2015) for the overflow gravity
current to estimate the changes in the vorticity and potential vorticity of the
flow over the Absheron sill; the effects of entrainment and friction are also
considered. Due to the importance of the overflow with respect to deep water
ventilation, a simple dynamical model of the boundary currents based on the
shape of the Absheron Strait is used to estimate typical mass transport and
flushing time; the flushing time is found to be about 15 to 20 years for the southern
basin of the Caspian Sea. This timescale is important for the region's
ecosystem and with respect to the impacts of pollution due to oil exploration.
In addition, by reviewing the drilled oil and gas wells in the Caspian Sea, the
results show that the deep overflow moves over some of these wells. Thus, the
deep flow could be an important factor influencing oil pollution in the deeper region of
the southern Caspian Sea.
THE INFLUENCE OF OIL PRODUCTION ON AQUATIC ORGANISMS OF THE CASPIAN SEA
