Earth’s largest inland body of water has been slowly evaporating for the past two decades due to rising temperatures associated with climate change, a new study finds.
Water levels in the Caspian Sea dropped nearly 7 centimeters (3 inches) per year from 1996 to 2015, or nearly 1.5 meters (5 feet) total, according to the new study. The current Caspian Sea level is only about 1 meter (3 feet) above the historic low level it reached in the late 1970s.
Increased evaporation over the Caspian Sea has been linked to increased surface air temperatures. According to the data from the study, the average yearly surface temperature over the Caspian Sea rose by about 1 degree Celsius (1.8 degrees Fahrenheit) between the two time frames studied, 1979-1995 and 1996-2015. These rising temperatures are likely a result of climate change, according to the study’s authors.
Evaporation brought about by warming temperatures appears to be the primary cause of the current drop in sea level and the decline will likely continue as the planet warms, according to the study’s authors.
“From our point of view as geoscientists, it’s an interesting place because it’s possible to construct a sort of budget for the total amount of water that’s there,” said Clark Wilson, a geophysicist with the Jackson School of Geosciences at the University of Texas at Austin, and co-author of the new study published in Geophysical Research Letters, a journal of the American Geophysical Union. “The real control that causes it to go up and down over long periods of time is really most likely the evaporation, which is almost completely dominated by temperature.”
The Caspian Sea, located between Europe and Asia, is roughly the size of Montana at 371,000 square kilometers (143,244 square miles). It has experienced substantial changes in its water level over the past several hundred years, but previous studies were unable to nail down the exact causes of the sea level changes.
The Caspian Sea is bordered by five countries and contains an abundance of natural resources and diverse wildlife. The sea also contains oil and natural gas reserves, and is an important resource for fisheries in the surrounding countries.
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Image via Jianli Chen, American Geophysical Union