Speaker 1: Welcome to brain stuff from how stuff Works a brain stuff,
Speaker 1: I'm Christian Sager. When the ancient Romans arrived at the
Speaker 1: Caspian Sea a couple of thousand years ago, they thought
Speaker 1: they'd arrived at an ocean. That's because the water they
Speaker 1: encountered was salty. Nestled amongst modern day Russia, Kazakhstan, Turkmenistan, Azerbaijan,
Speaker 1: and Iran, the Caspian Sea actually is the world's largest lake.
Speaker 1: For comparison, Lake Superior is the world's largest freshwater lake,
Speaker 1: with the surface area of thirty one thousand, seven hundred
Speaker 1: square miles or eighty two thousand, one hundred square kilometers.
Speaker 1: The Caspian Sea occupies a space significantly larger, at a
Speaker 1: hundred and forty three thousand, two hundred square miles or
Speaker 1: three hundred and seventy one thousand square kilometers for a
Speaker 1: US reference, that's like comparing the sizes of Maryland and Montana.
Speaker 1: The Caspian seas waters are brackish, about a third as
Speaker 1: salty as most ocean water. Because the water finds its
Speaker 1: way into it from about a hundred and thirty different
Speaker 1: freshwater sources. It has no outlet. If water is going
Speaker 1: to escape the Caspian Sea, it's got to do it
Speaker 1: through evaporation. So it's strange that the water level of
Speaker 1: the Caspian Sea has been steadily dropping for the past
Speaker 1: couple of decades. Between nineteen six and two thousand and fifteen,
Speaker 1: the sea has drawn down about three inches or seven
Speaker 1: centimeters per year. That's about five ft or one point
Speaker 1: five meters total. This is not the first time water
Speaker 1: levels in the Caspian have dramatically dropped. Over the course
Speaker 1: of the twenty century. Changes in agricultural practices in its basin,
Speaker 1: as well as industry in damming in the Vulgar River,
Speaker 1: which accounts for eighty percent of the inflow of water,
Speaker 1: all of it pulled the seed down the three feet
Speaker 1: or one me or below what it is today by
Speaker 1: the late nineteen seventies. But a new study published in
Speaker 1: Geophysical Research Letters finds that the Caspian seas current shrinking
Speaker 1: is due to the water simply evaporating away, driven by
Speaker 1: increasing average atmospheric temperatures. The researchers found that between the
Speaker 1: two time frames they studied the years between nineteen seventy
Speaker 1: nine and nine, and then again between nine and fifteen,
Speaker 1: the average yearly air temperatures directly above the sea rose
Speaker 1: by about one point eight degrees fahrenheit or one degree celsius. Now.
Speaker 1: Co author Clark Wilson said, what really controls the sea
Speaker 1: going up and down over long periods of time is
Speaker 1: most likely evaporation, which is almost completely dominated by temperature.
Speaker 1: This study is the first to provide convincing evidence that
Speaker 1: the Caspian Seas water levels are changing due to evaporation
Speaker 1: and a changing climate, rather than things like changes in
Speaker 1: river discharge or rainfall. If the trend continues, evaporation will
Speaker 1: have the biggest impact on the shallowest parts of the
Speaker 1: sea first. Much of the water at the sea's northern tip,
Speaker 1: for instance, is only about sixteen feet or five meters deep.
Speaker 1: At this rate of evaporation, that portion will disappear within
Speaker 1: seventy five years. Cities currently located on the shore would
Speaker 1: quite quickly become landlocked as waters recede, and many of
Speaker 1: these population centers derive significant economic value from the sea,
Speaker 1: from tourism to fishing to shipping. Additionally, the Caspian Sea
Speaker 1: is home to some pretty crazy ancient animals that would
Speaker 1: be out of a home if the sea disappeared. The
Speaker 1: Caspian was part of the Teta's Ocean about three hundred
Speaker 1: million years ago. Relatives of some of those species remain,
Speaker 1: including a whopping of the world's caviare producing and endangered sturgeon.
Speaker 1: Today's episode was written by Jesslyn Shields, produced by Dylan Fagan,
Speaker 1: and For more on this and other topics, please visit
Speaker 1: us at how stup works dot com.