People have built so many dams around the world that the bars of the Earth have gone from the rotating axis of the planet, new research suggests.
Over the last 200 years, people have built nearly 7,000 massive dams, pushing enough Geophysical research letters.
This drift is possible because the solid shell of the earth forms a hard bark around a molten layer of gooey magma. This means that every time a major amount of mass is redistributed through the surface of the planet, the outer rock layer is rocking, changing in relation to the molten interior of the Earth. When this happens, different areas on the surface of the Earth end directly above the rotating axis of the planet. As a result, the poles of the planet go through different surface places than before, a phenomenon known as true polar wandering.
“As we catch water behind dams, not only does it remove water from the oceans – thus leading to a global sea level fall – it also redistributes a multitude around the world,” Natasha Valencic, a graduate student from Harvard University and chief author of the new study, said in Statement.
In the study, Valencic and her team analyzed a previously published global database of dams to calculate their locations, the volume of water they store, and how that stored water affected the mass distribution of the earth. Previously, the database revealed that 6,862 large dams built between 1835 and 2011 contributed to a decrease in sea levels. Collectively, these dams hold enough water to fill the big canyon twice.
The results showed that global construction of dams caused the Poles of the Earth to change in two phases. The first phase, from 1835 to 1954, coincided with an explosion in dam construction in North America and Europe. These areas changed to the equator, and as a result, the North Pole moved about 8 inches (25 centimeters) to the 103rd Meridian East, a line that passes through Russia, Mongolia and China.
During the second wave of dam construction, between 1954 and 2011, most dams were built in Asia and East Africa. As a result, the North Pole changed 22 inches (57 centimeters) to the 117th Meridian -West, which crosses western South America and the South Pacific. Polar wander is not linear; Instead, it follows a floating path, so the whole move is not added exactly to 3.7 feet.
While the results are relatively subtle, they emphasize the need for researchers to calculate water stored in dams when predicting a future sea level increase. In the twentieth century, global sea levels rose 4.7 to 6.7 inches (12 to 17 centimeters), but people captured about a quarter of that volume behind dams, according to Valencic.
“Depending on where you put dams and reserves, the geometry of sea level rise will change,” she said. “This is another factor we need to consider because these changes can be quite large and significant.”
