Abstract. Decadal variability in Caspian Sea thermohaline properties is
investigated using a high-resolution ocean general circulation model
including sea ice thermodynamics and air–sea interaction forced by prescribed
realistic atmospheric conditions and riverine runoff. The model describes
synoptic, seasonal and climatic variations of sea thermohaline structure,
water balance, and sea level. A reconstruction experiment was conducted for
the period of 1961–2001, covering a major regime shift in the global climate
during 1976–1978, which allowed for an investigation of the Caspian Sea response to
such significant episodes of climate variability. The model reproduced sea
level evolution reasonably well despite the fact that many factors (such as possible
seabed changes and insufficiently explored underground water
infiltration) were not taken into account in the numerical reconstruction.
This supports the hypothesis relating rapid Caspian Sea level rise in
1978–1995 with global climate change, which caused variation in local
atmospheric conditions and riverine discharge reflected in the external
forcing data used, as is shown in the paper. Other effects of the climatic shift
are investigated, including a decrease in salinity in the active layer,
strengthening of its stratification and corresponding diminishing of
convection. It is also demonstrated that water exchange between the three
Caspian basins (northern, middle and southern) plays a crucial role in the
formation of their thermohaline regime. The reconstructed long-term trends in
seawater salinity (general downtrend after 1978), temperature (overall
increase) and density (general downtrend) are studied, including an
assessment of the influence of main surface circulation patterns and model
error accumulation.
Long-term evolution of Caspian Sea thermohaline properties reconstructed in an eddy-resolving ocean general circulation model
