ID : N-222 Date : 2017/08/30 - 15:00
(Persia digest)- An article in the Daily Mail reports that water levels in the Caspian have dropped a total of 1.5 meters (5 feet) since 1996. The current sea level is only about 1 meter (3 feet) above the historic 1970's low. The evaporation over the Caspian is linked to increased surface air temperatures. The increase in air temperatures is likely due to climate change, and the decrease in water levels could threaten spawning grounds for unique species.
Water in the Caspian Sea, Earth's largest inland body of water, has been slowly evaporating for the past twenty years - and a new study has pinpointed why. Water levels in the Caspian Sea, located between Europe and Asia, have dropped nearly seven centimeters (3 inches) per year, from 1996 to 2015 - a total of 1.5 meters (5 feet). The Caspian Sea has experienced substantial changes in its water levels over the past several hundred years, but previous studies were unable to nail down the exact causes of the changes.
According to data from the study, published in Geophysical Research Letters, the average yearly surface temperature of the Caspian Sea rose by about 1 degree (1.8 degrees Fahrenheit) between the two time frames studied, 1979-1995 and 1996-2015.
Evaporation brought about by global warming temperatures appears to be the primary cause of the current drop in sea levels, 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 in Austin, and co-author of the new study.
The researchers looked at the three primary influences on the Caspian Sea's water levels: water from rivers that drain into the sea, precipitation and evaporation. '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 is bordered by five countries and contains a vast amount of natural resources and diverse marine life. The Sea also contains oil and natural gas reserves, and is an important resource for fisheries in the surrounding countries.
The Caspian reached an all-time historic low of 29 meters (95 feet) below mean sea levels in the late 1970s, before water levels increased in 1978.
The study provides the first convincing evidence that increased evaporation over the Caspian Sea is a more important driver of Sea level changes than river discharge or precipitation. According to the researchers, if current evaporation rates continue, the sea could approach this low again. Evaporation will have the biggest impact on the northern part of the Caspian Sea because most of the water in that area is less than 5 meters (16 feet) deep. If the current rate of a 7-centimeter decrease per year trend continues, it will take 75 years for the northern part of the Sea to disappear.
This could impact unique, ancient species in the Sea remaining from when it was part of the Tethys Ocean 300 million years ago - during the Mesozoic era. The fall in sea levels would also impact the Kara-Bogaz-Gol Bay on the eastern side of the Sea, which is less than 5 meters (16 feet) deep and contains one of Earth's largest natural deposit of sea salts.