Welcome to brain stuff from how stuff Works a brain stuff, I'm Christian Sager. When the ancient Romans arrived at the Caspian Sea a couple of thousand years ago, they thought they'd arrived at an ocean. That's because the water they encountered was salty. Nestled amongst modern day Russia, Kazakhstan, Turkmenistan, Azerbaijan, and Iran, the Caspian Sea actually is the world's largest lake.
For comparison, Lake Superior is the world's largest freshwater lake, with the surface area of thirty one thousand, seven hundred square miles or eighty two thousand, one hundred square kilometers. The Caspian Sea occupies a space significantly larger, at a hundred and forty three thousand, two hundred square miles or three hundred and seventy one thousand square kilometers for a US reference, that's like comparing the sizes of Maryland and Montana.
The Caspian seas waters are brackish, about a third as salty as most ocean water. Because the water finds its way into it from about a hundred and thirty different freshwater sources. It has no outlet. If water is going to escape the Caspian Sea, it's got to do it through evaporation. So it's strange that the water level of the Caspian Sea has been steadily dropping for the past
couple of decades. Between nineteen six and two thousand and fifteen, the sea has drawn down about three inches or seven centimeters per year. That's about five ft or one point five meters total. This is not the first time water levels in the Caspian have dramatically dropped. Over the course
of the twenty century. Changes in agricultural practices in its basin, as well as industry in damming in the Vulgar River, which accounts for eighty percent of the inflow of water, all of it pulled the seed down the three feet or one me or below what it is today by the late nineteen seventies. But a new study published in Geophysical Research Letters finds that the Caspian seas current shrinking is due to the water simply evaporating away, driven by
increasing average atmospheric temperatures. The researchers found that between the two time frames they studied the years between nineteen seventy nine and nine, and then again between nine and fifteen, the average yearly air temperatures directly above the sea rose by about one point eight degrees fahrenheit or one degree celsius. Now.
Co author Clark Wilson said, what really controls the sea going up and down over long periods of time is most likely evaporation, which is almost completely dominated by temperature. This study is the first to provide convincing evidence that the Caspian Seas water levels are changing due to evaporation and a changing climate, rather than things like changes in river discharge or rainfall. If the trend continues, evaporation will have the biggest impact on the shallowest parts of the
sea first. Much of the water at the sea's northern tip, for instance, is only about sixteen feet or five meters deep. At this rate of evaporation, that portion will disappear within seventy five years. Cities currently located on the shore would quite quickly become landlocked as waters recede, and many of these population centers derive significant economic value from the sea,
from tourism to fishing to shipping. Additionally, the Caspian Sea is home to some pretty crazy ancient animals that would be out of a home if the sea disappeared. The Caspian was part of the Teta's Ocean about three hundred million years ago. Relatives of some of those species remain, including a whopping of the world's caviare producing and endangered sturgeon.
Today's episode was written by Jesslyn Shields, produced by Dylan Fagan, and For more on this and other topics, please visit us at how stup works dot com.