Climate change causing Caspian Sea to evaporate: Study

Water levels in the Caspian Sea dropped nearly seven centimetres per year from 1996 to 2015, or nearly 1.5 metres total, according to the findings published in the journal Geophysical Research Letters.

According to the data from the study, the average yearly surface temperature over the Caspian Sea rose by about one degree Celsius between the two timeframes studied, 1979-1995 and 1996-2015. These rising temperatures are likely a result of climate change, the study said.

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, the researchers said.

"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 study co-author Clark Wilson, a geophysicist with the Jackson School of Geosciences at the University of Texas in Austin.

"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," Wilson said.

The Caspian Sea, located between Europe and Asia, covers roughly 371,000 square kilometres. The sea contains oil and natural gas reserves, and is an important resource for fisheries in the surrounding countries.

The researchers looked at the three primary influences on Caspian Sea water levels — water from rivers that drain into the sea, precipitation and evaporation. They compiled information about water level changes observed by satellites, records of precipitation and drainage into the sea from rivers, and estimations of precipitation and evaporation from climate models.