The water level in the largest closed water body on Earth during the last 20 years falls by seven centimeters per year. The total decrease since 1996 was about 1.5 meters. Today’s level is just one meter higher than the record low level of the late 1970s.
The article with the results of analysis of long-term observations is published in the journal Geophysical Research Letters.
According to the results of the new work, the average near-surface temperature near the Caspian Sea increased by about 10C, if we compare two time periods studied: from 1979 to 1995 and from 1996 to 2015.
The authors believe that this increase is a manifestation of global warming, which affected the fact that the intensity of evaporation increased. This, in turn, led to a lowering of the water level.
“We are attracted to this place by geologists, because here you can build something like a general water balance,” says Clark Wilson of the University of Texas at Austin. “The real reason for the changes in the water level for a long time is probably evaporation, which is almost completely controlled by temperature.”
The authors were interested in this task when they helped calibrate the data of the GRACE geophysical satellite and noticed the multimetric changes in the water level. They considered three main factors: the flow of water with rivers, atmospheric precipitation and evaporation. By combining satellite water level measurements, sediment and river flow data, and climate modeling results, scientists have identified the impact of each factor on the observed change in the level from 1979 to 2015. Evaporation has been responsible for about half of the water level drop, and a further increase in temperature can only exacerbate the situation.