Since the 19th century, humans have built nearly 7,000 dams, causing enough water to fill the Grand Canyon twice. These infrastructure, by moving huge liquid masses, influenced earth rotation. The consequences, although minimal, shed light on the interactions between human and geophysical activities.
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How the dams move the poles
The terrestrial crust, solid but flexible, is based on a layer of viscous magma. Any mass redistribution to surfacelike the melting of ice or water storage, causes an adjustment of this external envelope. The dams, retaining billions of tonnes of water, thus generated a shift progressive poles.
Between 1835 and 2011, this accumulation of water led to the movement of the poles of approximately 1.1 meters. The researchers identified two distinct phases, corresponding to the waves of construction in America of the Nord and in Europethen in Asia and Africa. Each period oriented the North Pole towards different meridians.
This phenomenon, called “true polar displacement”, remains without direct impact on the climate. However, he highlights the magnitude of the modifications induced by man. The dams also contributed to a temporary drop in the average level of mers the 21 mm.
Implications for climate study
Artificial tanks have masked part of the historic elevation of the oceans. In the 20th century, they retained the equivalent of 25 % of the expected increase. This given must now be integrated into climatic models to refine projections.
The location of dams also influences the regional distribution of the rise of waters. The regions close to the large tanks could undergo specific variations, depending on the calculations of the scientific team. These effects, although subtle, require increased attention.
Finally, this study offers a framework to anticipate future polar trips linked to the melting of glacial caps. The mechanisms highlighted help to understand how the Terre reacts to mass redistributions, whether natural or anthropogenic (caused by humans).
