Rising temperatures causing Caspian sea to evaporate, study finds

By Azernews

By Amina Nazarli

The Caspian Sea, 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.

In case current climate models continue, the northern waters of the Sea, which lies between Europe and Asia, can disappear within 75 years.  

The researchers announced their shocking findings in a study published in Geophysical Research Letters, a journal of the American Geophysical Union.

Water levels in the Caspian Sea have dropped nearly seven centimeters (3 inches) per year, from 1996 to 2015 - a total of 1.5 meters (5 feet). The current sea level is only about 1 meter (3 feet) above the historic low level it reached in the late 1970s.

The Caspian reached an all-time historic low of 29 meters (95 feet) below mean sea levels in the late 1970s, before water levels jumped in 1978. 

The increased evaporation over the Caspian Sea has been linked to increased surface air temperatures, likely due to climate change, and the decrease in water levels could threaten shallow spawning grounds for unique species. 

The study shows that the average yearly surface temperature over the Caspian Sea rose by about 1 degree Celsius (1.8 degrees Fahrenheit) between the two timeframes studied, 1979-1995 and 1996-2015.  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 Dr Clark Wilson, a geophysicist with the Jackson School of Geosciences at the University of Texas at Austin, and co-author of the new study. 

“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.”

Evaporation contributed to about half of that decline, and the combined effects of precipitation and river discharge changes contributed to the other half.  Although the observed evaporation rates are linked with increased surface air temperatures, they're also associated with other factors such as surface humidity and wind. 

At 1,200 km long, 320 km wide, and with a surface area of approximately 371,000 km2, the Caspian Sea is the largest completely enclosed body of water on Earth. The sea receives water from the Volga, Ural and the Kura rivers and numerous other freshwater inputs, but has no outlet to the world's oceans. The Volga River, the largest in Europe, is the source of 80% of the Caspian's freshwater inflow.

This landlocked mega lake bordered by five countries including Azerbaijan, Russia, Kazakhstan, Iran and Turkmenistan contains an abundance of natural resources and diverse wildlife. The sea is rich with oil and natural gas deposits, and is an important resource for fisheries in the surrounding countries.

Director of the Institute of Geography of ANAS Ramiz Mammadov, commenting on the new study, does not entirely agree with the opinion that in case of global warming, the Caspian Sea will dry only on the territory of Russia and Kazakhstan.

“A decrease in the water level in the Caspian Sea may cause shoaling in other Caspian countries, including shallow water in Azerbaijan,” he said. “Global warming and a decrease in sea level will affect the entire coastal zone and shallow areas.”

Mammadov told APA that the level of the Caspian Sea falls yearly.

 "This in turn creates problems in the coastal areas of the Sea, in particular, in shallow water areas. Most of the shallow water falls on the northern Caspian - the territories of Kazakhstan and Russia. Here the average depth is 7 meters. A fall in the water level may lead to a decrease in water, create problems for biodiversity and shipping,” he said.

Mammadov warned that this will also hugely affect Azerbaijan. “This can create problems in Neftchala region, where the depth of the coastal zone is small. Such problems can appear on the Lankaran lowland, even in Khachmaz and Sumgayit,” he said.

The expert added that no one can guarantee that in the near future the decline in water will increase or, conversely, decrease; noting that the change in the level of the Caspian Sea is associated with climate change, which makes long-term forecasting impossible.