The Caspian, classified alternately as an inland sea and as a lake, is the world’s largest inland water body and is fed primarily by four rivers: the Volga (90% of input), the Kura Araks (6.3%), the Ural (3%) and the Terek (2.5%). River inputs have been declining in recent years, and climate models predict that input to fall still further in decades ahead, leading to a potential sea level fall of 9-18 m/29-51 ft.
Caspian drainage basins.
Recent studies have shown that discharge of the Volga River, which in recent years has averaged 8,060 cu m/s (285,000 cu ft/s) flow rate, has decreased significantly since 1946. The river’s drainage basin is almost entirely within Russia, draining the western plains including its tributary Moskva which runs through Moscow. Climate models show a continuation of this trend, for increasing variability but an overall decline in precipitation within the Volga’s basin.
Predicted Caspian sea level loss by 2100.
The Caspian region has nearly doubled global temperature increase over the past 120 years, rising more than 2ºC/3.6ºF. The three more severe climate projections (and the world is currently on track for at least the lowest of these three) show regional average temperature increase of 1.7-3.5ºC/3.1-6.3ºF increase by 2100. This will increase evaporation rates and speed up the drop in sea level.
Caspian beluga (sturgeon).
Sea level drop that large will be catastrophic for nearly all coastal towns and cities. It will also have huge effects on the ecosystems due to loss of habitat—an 18 m decrease will lead to a loss of 1/3 of the Caspian’s surface area—and changing chemistry. The already brackish water will become more so, endangering many species with narrow salinity tolerances. Larger species such as the Caspian seal, which depends on sea ice for its winter habitat, and the Caspian beluga (sturgeon) will have far smaller ranges. (With brackish enough water, and loss of the northern portion of the sea, Caspian sea ice might disappear altogether, and the seals with it.) “An ecocide,” echoing descriptions of Easter Island, is how some scientists refer to the Caspian’s possible fate.
Baby Caspian seal.
Tomorrow: the death of the Aral Sea.
Be brave,
and be well.
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