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Over the past two centuries, humans have locked up enough water in dams to shift Earth’s poles slightly away from the planet’s axis of rotation, according to new research.

Earth’s outermost solid layer sits atop goopy molten rock, so it can move relative to the magma below it. Anytime mass is redistributed around the planet’s surface, like when ice sheets grow or shrink, this outermost rock layer wobbles and moves around. Imagine slapping a lump of clay onto one side of a spinning basketball: to maintain momentum, the part of the ball with the clay on it will shift slightly toward its equator and away from its axis of rotation. When this happens on Earth and the outermost rock layer wobbles around, different areas of the surface end up sitting directly over the axis of rotation. The geographic poles then pass through different spots on the surface than before, a process called true polar wander.

A new study in Geophysical Research Letters finds the construction of nearly 7,000 dams from 1835 to 2011 shifted the poles about a meter (3 feet) in total and caused a 21-millimeter (0.83-inch) drop in global sea levels. Together, these dams hold enough water to fill the Grand Canyon twice.

The results demonstrate another way human activities have affected the planet, according to the study authors. The polar shift is small, but it could help scientists understand how the poles will move if major glaciers and ice sheets melt due to climate change.

“As we trap water behind dams, not only does it remove water from the oceans, thus leading to a global sea level fall, it also distributes mass in a different way around the world,” said Natasha Valencic, a graduate student in Earth and planetary sciences at Harvard University and lead author of the new study. “We’re not going to drop into a new ice age, because the pole moved by about a meter in total, but it does have implications for sea level.”

In the new study, Valencic and her colleagues used a global database of dams to map the locations of each dam and the amount of water each impounds. They analyzed how the water impoundment from 6,862 dams shifted Earth’s poles from 1835 to 2011.

Their results showed global dam building caused Earth’s poles to shift in two distinct phases. From 1835 to 1954, many dams were built in North America and Europe, shifting these areas toward the equator. The North Pole moved 20.5 centimeters (8 inches) toward the 103rd meridian east, which passes through Russia, Mongolia, China, and the Indochina Peninsula.

Then, from 1954 to 2011, dams were built in East Africa and Asia, and the pole shifted 57 centimeters (22 inches) toward the 117th meridian west, which passes through western North America and the South Pacific.

Over the entire period from 1835 to 2011, the poles moved about 113 centimeters (3.7 feet), with about 104 centimeters (3.4 feet) of movement happening in the 20th century.

The results show that researchers need to take water impoundment into consideration when calculating future sea level rise. In the 20th century, global sea levels rose by 1.2 millimeters per year on average, but humans trapped a quarter of that amount behind dams – a significant fraction, according to Valencic. And sea level rise does not happen uniformly around the globe.

“Depending on where you place dams and reservoirs, the geometry of sea level rise will change,” she said. “That’s another thing we need to consider, because these changes can be pretty large, pretty significant.”

Astronomers have made significant strides in understanding how planets like the ones in our solar system form by detecting planet-forming “pebbles” around two young stars

These tiny rocky particles were discovered orbiting DG Tau and HL Tau, two stars located approximately 450 light-years from Earth, providing a rare opportunity to understand the earliest stages of planetary formation.

Planetary seeds in action

The new observations show large reservoirs of solid material, or pebbles, in the wide discs of dust and gas that surround these young stars. These discs, known as protoplanetary discs, are the birthplaces of planets.

Over time, these tiny pebbles clump together, forming larger and larger bodies that eventually create planets like Earth, Jupiter, and other worlds in our solar system.

The importance of this discovery lies in the fact that these pebbles have been found at distances similar to Neptune’s orbit, which suggests that the entire planetary system could be forming right now in these distant stellar nurseries.

Understanding the missing link in planet formation

Although astronomers have always known that dusty discs often surround young stars and have discovered thousands of fully formed planets in other star systems, the in-between stage has always been much harder to observe.

Astronomers struggle with determining the size of the particles; smaller grains are easily visible using optical and infrared telescopes, but as the grains grow and clump into larger pebbles, their surface area decreases, making them harder to detect.

To solve this mystery, astronomers used MERLIN, which is a unique array of seven radio telescopes spread across the UK. This robust network is capable of detecting the radio signals emitted by centimetre-sized pebbles, which shine brightest at similar wavelengths.

A breakthrough using e-MERLIN

Using e-MERLIN, researchers captured a striking image of DG Tau’s disc showing centimetre-sized pebbles already present at long distances from the central star. A similar pattern of rocky seeds has also been observed around HL Tau. These findings suggest that planet formation begins much earlier and farther out than previously understood.

The project behind this breakthrough is known as PEBBLeS (Planet Earth Building-Blocks – a Legacy eMERLIN Survey), a large-scale effort to map and study the building blocks of future planetary systems.

The success of e-MERLIN will soon enable more powerful observations. The upcoming Square Kilometre Array (SKA) telescopes, currently under development in South Africa and Australia, will increase astronomers’ ability to study protoplanetary discs. With greater sensitivity and resolution, the SKA will be able to observe hundreds of developing planetary systems across our galaxy.

When science operations with the SKA-Mid telescope begin in 2031, researchers will be ready to build on the work started with e-MERLIN.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors.

Source: Perspectives of Earth and Space Scientists

Our modern society is increasingly reliant on multiple technologies that are vulnerable to the adverse effects of space weather. This necessitates effective public communication and awareness of various space weather phenomena as well as increased public engagement and preparedness for risk mitigation.

Chabanski et al. [2025] advocate for the development and implementation of a standardized naming convention of geomagnetic storms, along the lines of existing naming conventions in meteorology, astronomy, and geography.

The authors surveyed the top 50 geomagnetic storms over the past 47 years (since 1978), of which only five had names assigned by the scientific community. Drawing on lessons learned in other scientific disciplines, they propose the possible formation of an international working team comprised of International Space Weather Coordination Forum participants. This international team would implement a theoretical framework and a unified international standard for defining the criteria, protocols, and procedures for naming and cataloguing geomagnetic storms based on their minimum Disturbance Storm Time (Dst) indices and their solar origins.

This proposed initiative is about not only assigning names to geomagnetic storms but also empowering the public with the knowledge necessary to navigate the challenges of the 21st-century space environment.

Citation: Chabanski, S., de Montety, F., Lilensten, J., Poedts, S., & Spogli, L. (2025). The power of a name: Toward a unified approach to naming space weather events. Perspectives of Earth and Space Scientists, 6, e2025CN000285. https://doi.org/10.1029/2025CN000285

—Andrew Yau, Editor, Perspectives of Earth and Space Scientists

Text © 2025. The authors. CC BY-NC-ND 3.0
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