Man-made dams have shifted Earth’s poles, says study

New research suggests that the construction of thousands of dams globally since 1835 has caused Earth’s poles to “wobble” or “wander.” This phenomenon is due to the massive amount of water held behind these dams, which redistributes mass across the planet.

Key findings and explanations:

• Mass Redistribution: Large dams impound vast quantities of water, altering the distribution of mass on Earth’s surface. This shift in mass causes the Earth’s solid crust to move relative to its gooey mantle, a process known as true polar wander.
• True Polar Wander: Any significant movement of mass within the Earth or on its surface changes the orientation of the planet’s rotation axis relative to the crust. This means the geographic locations of the North and South Poles change.
• Impact on Sea Level: As water is trapped behind dams, it is removed from the oceans, contributing to a slight global sea level fall. However, this also redistributes mass in a way that influences polar motion.
• Magnitude of Shift: The study, published on May 23, 2025, in the journal Geophysical Research Letters, analyzed the impact of nearly 7,000 dams built between 1835 and 2011. It found that this dam construction caused a total polar shift of approximately 3.7 feet (1.1 meters) over that period, along with a roughly 0.9-inch (23 millimeters) drop in global sea levels.
• Other Human Impacts: Scientists were already aware that other human activities affecting water distribution can cause polar wander:
  • Ice Melt: Dramatic ice melt due to climate change is projected to move the poles by 90 feet (27 meters) by the end of this century.
  • Groundwater Extraction: A 2023 study concluded that groundwater extraction between 1993 and 2010 resulted in a polar drift of 31 inches (80 centimeters).
• Implications: While the direct impact of a few feet of polar shift on daily life is minimal, this research highlights how significant human infrastructure can physically alter the planet. It underscores the need to account for the effects of dams in future climate and sea-level forecasts.

(Source: Live Science)