Recent research has shown that thousands of dams built since 1835 have caused shifts in Earth’s poles. Scientists discovered that the massive amounts of water stored behind these dams redistribute weight, affecting the position of the crust above the liquid mantle of our planet.
The Earth’s mantle is like a thick liquid layer, allowing the solid crust to shift above it. When large volumes of water are displaced, it can affect the location of the poles. Researchers call this phenomenon “true polar wander.”
A relevant study from March found that climate change-related ice melt could move Earth’s poles by up to 90 feet (27 meters) by 2100. Additionally, a 2023 study linked groundwater extraction from 1993 to 2010 to a polar drift of 31 inches (80 centimeters).
In the latest study, scientists examined 6,862 dams built globally from 1835 to 2011. They tapped into an existing database showing that these dams hold enough water to fill the Grand Canyon twice, leading to a drop in global sea levels of 0.9 inches (23 millimeters).
Storing water behind dams caused the Earth’s poles to shift by a total of 3.7 feet (1.1 meters) during the research period. Lead author Natasha Valencic, a geology and geophysics student at Harvard, noted, “When we trap water, we change its mass distribution across the globe.”
The study identified two waves of polar movement. The first, from 1835 to 1954, was linked to dam construction primarily in North America and Europe, causing the North Pole to shift 8 inches (20 centimeters) towards the 103rd meridian in Asia.
The second phase spanned from 1954 to 2011, focusing on dam expansion in East Africa and Asia. This construction led to a more significant shift of 22 inches (57 centimeters) towards the 117th meridian, affecting North America and the South Pacific. The shifts are not linear, which explains the total movement of 3.7 feet.
While the pole’s movements may seem minor, they can have significant repercussions on sea levels. “We won’t enter a new ice age because the poles moved by about a meter, but it does affect sea levels,” Valencic explained. Scientists now argue that these shifts need to be considered in sea-level rise predictions, given that dams block nearly a quarter of water that would typically flow into oceans. The global sea level rose by **4.7 to 6.7 inches (12 to 17 cm)** in the 20th century, with a significant portion of that water held behind dams.
The relationship between dam construction and climate change is complex but crucial for understanding our planet’s future. As scientists and policymakers grapple with the implications, recognizing these changes may help us make more informed decisions regarding water management and environmental policies.
For more on sea-level rise and its implications, check out [Smithsonian Ocean](https://ocean.si.edu/through-time/ancient-seas/sea-level-rise).
