Overview

• A study in Geophysical Research Letters shows that water trapped behind about 7,000 dams since 1835 has driven true polar wander, moving Earth’s geographic poles by roughly one meter.
• Impounded reservoirs hold enough water to fill the Grand Canyon twice, causing a 21 millimeter drop in global sea levels and offsetting about a quarter of 20th century rise.
• Dam construction unfolded in two phases: North American and European projects from 1835 to 1954 nudged the pole toward Russia and China, while Asian and East African builds from 1954 to 2011 steered it back toward North America and the South Pacific.
• The research highlights that where dams are placed alters the geometry of sea level change, potentially skewing regional projections of ocean rise.
• Lead author Natasha Valencic and colleagues stress the need to integrate artificial water impoundment into future climate models to improve the accuracy of sea level forecasts.