Climate Change’s Effects on Caspian Sea – February 6th, 201342.0N 50.0E
Containing some 18,800 cubic miles of water and covering more than 143,000 square miles, the Caspian Sea is the largest inland body of water on Earth. The Caspian is fed by 130 rivers, the most significant being the Volga, which enters from the north and accounts for about 80 percent of the inflowing waters.
A concern about the Caspian Sea is that, like its neighbor the Aral Sea, it may be on a path toward drying out. Dams built by the Soviet Union caused the sea to shrink dramatically in a mere thirty years, and today river water that feeds the Caspian is still being diverted for agriculture and other purposes, or is evaporating from upstream reservoirs.
But other scientists have concluded that the fate of the Caspian hinges not on dams but on climate change. Climate change may alter rainfall and the rate of water evaporation in river watersheds as well as evaporation from the sea itself. A one-foot drop in the Caspian Sea level in the second half of 2010 was attributed to unusually hot spring temperatures.
Higher temperatures during the past few years have also warmed the upper layer of the sea to greater depth, with adverse effects for certain aquatic taxa. The higher temperatures—and, especially in the south, the consumption of grazing zooplankton by M. leidyi—have also led to blooms of phytoplankton (eutrophication) in both the northern and southern parts of the Caspian (click here for images), which cuts oxygen levels needed by other organisms. Promoting eutrophication is the inflow of organic material from rivers and onshore industry and even untreated sewage from settled areas.
In addition, a trend toward warmer winters seems to be reducing the seasonal ice cover that forms in the northern section of the sea—ice cover that is prime breeding habitat for the seals (click here for more information). Such ice can be observed in this image.