Human-Made Dams Disrupt Geological Balance, Causing True Polar Wander | WPN World People News

According to a recent study published in Geophysical Research Letters, the large-scale construction of dams by humans over the past two centuries has not only affected sea levels but also subtly altered the distribution of Earth’s mass—causing a slight drift in the planet’s rotational axis. This phenomenon is known as True Polar Wander, referring to a shift in the geographic locations of the North and South Poles due to the redistribution of mass on Earth.

The study was led by Natasha Valencic, a graduate researcher in geology and planetary sciences at Harvard University. She pointed out that since 1835, over 6,860 major dams have been built worldwide, with a combined water storage capacity large enough to fill the Grand Canyon twice. These massive reservoirs have significantly changed the surface mass distribution of the Earth, causing the location of the geographic poles to shift by about 1.1 meters in total.

The research team further explained that the Earth’s crust floats atop the mantle, much like a wooden plank floating on thick soup. When large volumes of water are stored in specific regions, this “floating plank” shifts due to changes in gravity. By analyzing global dam databases and conducting physical simulations, researchers identified two major phases of polar movement:The first phase, from 1835 to 1954, saw intensive dam construction in North America and Europe, causing the North Pole to drift about 20 centimeters toward longitude 103°E.The second phase, from 1954 to 2011, involved large-scale dam building in Asia and East Africa, resulting in another shift of 57 centimeters toward longitude 117°W.

Importantly, this polar movement does not occur in a straight line but follows a wobbling curve. Therefore, the total displacements in different directions do not simply add up to 1.1 meters.

The study also highlighted the indirect impact of dams on sea level. Since large amounts of water are trapped in reservoirs and do not flow into the ocean, the rate of sea level rise in the 20th century was significantly suppressed. Although the average annual sea level rise at the time was about 1.2 millimeters, the study found that approximately one-quarter of this water was stored in man-made structures, effectively delaying the trend of sea level rise.

Valencic added that sea level changes are not uniform across the globe. They are influenced by the location of dams and the pattern of mass redistribution, leading to more pronounced variations in certain regions. She recommends that future climate models and sea level projections incorporate dam-induced water storage as a factor.

While polar drift is unlikely to directly trigger climate catastrophes or a new ice age, the study underscores the long-term geophysical consequences of human infrastructure. It offers a critical perspective for understanding how human activity is reshaping the Earth system.