Dams Cause Earth's Poles to Wander, Shifting the Planet's Axis
It's pretty wild to think about, but all those dams we've built are actually having a measurable effect on our planet. I'm talking about a real shift in the Earth's poles! According to a new study, the sheer amount of water we've held back with dams has caused the Earth's poles to wander.
Specifically, over the last couple of centuries, we've built almost 7,000 massive dams. That's a lot of concrete and a whole heap of water! All that stored water has been enough to nudge the Earth's poles by about a meter, which is roughly three feet. Besides that, it has caused a 21-millimeter drop in global sea levels, according to research in Geophysical Research Letters.
Now, how does this actually work? Well, the Earth's crust is like a hard shell floating on a layer of gooey magma. Because of this, when a significant amount of mass is redistributed across the planet’s surface, the Earth wobbles around its axis. Think of it like spinning a basketball - if you press down on one side, it is going to slightly change direction.
Natasha Valencic, the lead author of the study, pointed out that trapping water behind dams removes water from the oceans and redistributes mass around the world, leading to a sea level drop. I think this is a really interesting point, because it shows how interconnected everything is. We often think of these big engineering projects as isolated events, but they have global consequences.
The research team analyzed a database of dams, looking at their locations and the amount of water they hold. This data revealed that these dams have collectively trapped enough water to fill the Grand Canyon twice! And this has had a measurable impact on the Earth's poles.
Interestingly, the shift has happened in two phases. From 1835 to 1954, when most dams were being built in North America and Europe, the North Pole moved about 8 inches toward Russia, Mongolia, and China. The second phase, from 1954 to 2011, saw most dams constructed in Asia and East Africa, leading to a 22-inch shift toward western South America and the South Pacific. Polar wander doesn't occur in a straight line, it meanders. That's why the numbers aren't perfectly linear.
While these shifts might seem small, they highlight a crucial point: we need to consider the impact of dams when predicting future sea level changes. I think it's really important for researchers to take these factors into account. After all, you can't manage what you don't measure! In the 20th century, humans trapped about a quarter of the volume behind dams, and we need to understand the implications of that.
Valencic emphasized that the geometry of sea level rise will change depending on where dams and reservoirs are placed. This is a significant factor to consider, as these changes can be quite large. This goes to show that even things that might seem relatively localized can have a global ripple effect.
Source: Gizmodo