human activities

Between 1835 and 2011, humanity built nearly 7,000 barrages. Dams capable of retaining enough water to fill the Grand Canyon. Also enough to lower the sea level of almost 23 millimeters. And even to move the poles of our land by just over a meter, we tell us today researchers from the University of Harvard (United States).

Poles that move according to mass changes

To understand, it must be remembered that the coatcoat of our land is made up of a viscous melted rock. Above, a crustcrust solidsolid which can move. She does it every time the massemasse is redistributed to the surface of our planet. For example, when Glacial capsGlacial caps grow or decrease. There Ice Fonte Polar in the context of global warming could make them move from no less than 27 meters by 2100. To retain water in large quantities in certain regions has the same type of effect.

In Geophysical Research Lettersresearchers detail that the constructionconstruction Many dams in North America and Europe between 1835 and 1954 first moved the northern pole of 20.5 centimeters to 103^e meridianmeridian is the one who crosses Russia, Mongolia, China and the Indochinese peninsula. From 1954 to 2011, it was especially in East Africa and Asia that dams were built. Result, a movement of 57 centimeters around 117^e Meridian West, which crosses the west of North America and the South Pacific.

An influence on the elevation of sea level

What these works show above all is that it will be important to take these water deductions into account to calculate the future elevation of sea level under the effect of global warming.

Au XX^e century, the world level of oceans increased by 12 to 17 centimeters. But our dams held a quarter of this quantity. A significant fraction, especially since the dams also play on the geometry of the elevation. Depending on their locations, their effects are not the same. And the elevation of sea level changes.