WEBVTT - Why is the Caspian Sea Evaporating?

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<v Speaker 1>Welcome to brain stuff from how stuff Works a brain stuff,

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<v Speaker 1>I'm Christian Sager. When the ancient Romans arrived at the

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<v Speaker 1>Caspian Sea a couple of thousand years ago, they thought

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<v Speaker 1>they'd arrived at an ocean. That's because the water they

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<v Speaker 1>encountered was salty. Nestled amongst modern day Russia, Kazakhstan, Turkmenistan, Azerbaijan,

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<v Speaker 1>and Iran, the Caspian Sea actually is the world's largest lake.

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<v Speaker 1>For comparison, Lake Superior is the world's largest freshwater lake,

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<v Speaker 1>with the surface area of thirty one thousand, seven hundred

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<v Speaker 1>square miles or eighty two thousand, one hundred square kilometers.

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<v Speaker 1>The Caspian Sea occupies a space significantly larger, at a

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<v Speaker 1>hundred and forty three thousand, two hundred square miles or

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<v Speaker 1>three hundred and seventy one thousand square kilometers for a

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<v Speaker 1>US reference, that's like comparing the sizes of Maryland and Montana.

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<v Speaker 1>The Caspian seas waters are brackish, about a third as

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<v Speaker 1>salty as most ocean water. Because the water finds its

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<v Speaker 1>way into it from about a hundred and thirty different

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<v Speaker 1>freshwater sources. It has no outlet. If water is going

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<v Speaker 1>to escape the Caspian Sea, it's got to do it

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<v Speaker 1>through evaporation. So it's strange that the water level of

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<v Speaker 1>the Caspian Sea has been steadily dropping for the past

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<v Speaker 1>couple of decades. Between nineteen six and two thousand and fifteen,

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<v Speaker 1>the sea has drawn down about three inches or seven

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<v Speaker 1>centimeters per year. That's about five ft or one point

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<v Speaker 1>five meters total. This is not the first time water

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<v Speaker 1>levels in the Caspian have dramatically dropped. Over the course

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<v Speaker 1>of the twenty century. Changes in agricultural practices in its basin,

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<v Speaker 1>as well as industry in damming in the Vulgar River,

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<v Speaker 1>which accounts for eighty percent of the inflow of water,

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<v Speaker 1>all of it pulled the seed down the three feet

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<v Speaker 1>or one me or below what it is today by

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<v Speaker 1>the late nineteen seventies. But a new study published in

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<v Speaker 1>Geophysical Research Letters finds that the Caspian seas current shrinking

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<v Speaker 1>is due to the water simply evaporating away, driven by

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<v Speaker 1>increasing average atmospheric temperatures. The researchers found that between the

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<v Speaker 1>two time frames they studied the years between nineteen seventy

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<v Speaker 1>nine and nine, and then again between nine and fifteen,

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<v Speaker 1>the average yearly air temperatures directly above the sea rose

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<v Speaker 1>by about one point eight degrees fahrenheit or one degree celsius. Now.

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<v Speaker 1>Co author Clark Wilson said, what really controls the sea

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<v Speaker 1>going up and down over long periods of time is

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<v Speaker 1>most likely evaporation, which is almost completely dominated by temperature.

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<v Speaker 1>This study is the first to provide convincing evidence that

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<v Speaker 1>the Caspian Seas water levels are changing due to evaporation

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<v Speaker 1>and a changing climate, rather than things like changes in

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<v Speaker 1>river discharge or rainfall. If the trend continues, evaporation will

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<v Speaker 1>have the biggest impact on the shallowest parts of the

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<v Speaker 1>sea first. Much of the water at the sea's northern tip,

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<v Speaker 1>for instance, is only about sixteen feet or five meters deep.

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<v Speaker 1>At this rate of evaporation, that portion will disappear within

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<v Speaker 1>seventy five years. Cities currently located on the shore would

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<v Speaker 1>quite quickly become landlocked as waters recede, and many of

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<v Speaker 1>these population centers derive significant economic value from the sea,

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<v Speaker 1>from tourism to fishing to shipping. Additionally, the Caspian Sea

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<v Speaker 1>is home to some pretty crazy ancient animals that would

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<v Speaker 1>be out of a home if the sea disappeared. The

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<v Speaker 1>Caspian was part of the Teta's Ocean about three hundred

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<v Speaker 1>million years ago. Relatives of some of those species remain,

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<v Speaker 1>including a whopping of the world's caviare producing and endangered sturgeon.

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<v Speaker 1>Today's episode was written by Jesslyn Shields, produced by Dylan Fagan,

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<v Speaker 1>and For more on this and other topics, please visit

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<v Speaker 1>us at how stup works dot com.