Climate change is now impacting Earth's rotation

Earth’s rotation feels steady, but beneath that illusion of constancy lies a subtle truth: the planet’s spin is shifting. The axis around which Earth rotates isn’t fixed. It wanders, sways, and drifts. This movement, called polar motion, happens over days, decades, and even millennia.

Historically, scientists attributed these shifts to deep Earth processes like changes in the mantle or the fluid outer core. But over the past few decades, researchers have noticed something else at play.

Melting glaciers, retreating polar ice, and shifting water levels are now steering the planet’s spin. Climate change has become a major driver of Earth’s rotational behavior.

A new study by Mostafa Kiani Shahvandi and Benedikt Soja from ETH Zurich traces this transformation from 1900 to 2100. It combines historical data and future projections to explore how climate-related mass shifts have tilted and will continue to tilt the Earth’s axis.

Earth’s rotation axis slowly shifts

Polar motion refers to changes in the position of Earth’s rotation axis relative to its crust. This doesn’t mean the planet itself tilts dramatically, but that the axis slowly shifts position, like a spinning top that’s wobbling.

These shifts are measurable in centimeters or meters, but they carry real consequences. The motion arises from several causes.

Short-term fluctuations come from atmospheric pressure and ocean currents. Long-term drifts, however, involve deeper or broader processes.

Among these, recent work has shown that surface mass changes – especially those linked to climate – play a growing role. This includes melting polar ice sheets, retreating glaciers, and changing patterns of groundwater storage.

Collectively, these movements redistribute Earth’s mass, changing its balance and nudging the axis off its previous course. This study examines how that motion has evolved from 1900 and predicts its path until 2100 under different climate scenarios.

Climate shapes Earth’s future drift

To project the future, the authors used two distinct climate pathways. The first, RCP2.6, represents a low-emission future with significant mitigation. The second, RCP8.5, imagines a high-emission world with little control over greenhouse gas output.

Their models showed clear differences between these futures. Under RCP2.6, Earth’s rotational pole moves about 12 meters from its 1900 position by the year 2100. Under RCP8.5, the shift more than doubles to around 27 meters.

The scale of that motion is significant and carries practical implications. The melting of Greenland’s ice sheet is the largest contributor to this motion. Its location and pattern of mass loss drive the pole westward.

Antarctic melt, particularly under high emissions, contributes more to eastward drift. Global glaciers and groundwater changes also affect the pole’s path, but to a smaller degree.

Ice sheets pull the planet’s axis

The melting of polar ice is not symmetrical. Greenland lies in the Northern Hemisphere and its melt pushes Earth’s rotation axis toward the west.

Antarctica, especially the Amundsen Sea region in the west of the continent, pulls the axis in the opposite direction. Under high-emission scenarios, Antarctica loses more mass, which shifts the pole eastward more aggressively.

However, Greenland still dominates the trend, especially in the early 21st century. Its contribution is large under both climate scenarios, though it grows faster under RCP8.5. This imbalance means the Earth’s rotation axis doesn’t simply shift in one direction.

Instead, it weaves a path across the surface, determined by the changing locations and intensities of ice melt. These movements reflect broader patterns in climate and show how intimately Earth’s systems are connected.

Influences that affect Earth’s spin

Outside the poles, mountain glaciers also melt and move water into the oceans. These smaller ice bodies, though less massive, still shape polar motion. Their contribution varies by location.

Glaciers in the Himalayas, for example, influence the direction of drift more than others. In low-emission scenarios, glacier melt slows.

This leads to reduced influence on Earth’s spin, allowing the westward motion driven by Greenland to dominate. In high-emission futures, the increased melting adds more complexity to the pole’s path.

Groundwater also affects polar motion. When water is pumped for agriculture or drinking, it eventually flows into the ocean. That changes Earth’s mass distribution.

The study found that groundwater depletion, particularly in the Eastern Hemisphere, drives the pole eastward. Though its impact is smaller than ice melt, it accumulates steadily.

Predicting Earth’s spin

The researchers used sea-level equations and high-resolution mass data to simulate Earth’s rotation path. Their analysis stretched from historical observations to future projections, capturing both past behavior and what may come next.

However, predicting the future of polar motion isn’t simple. Some components, like groundwater, are hard to forecast accurately.

Many datasets lack short-term variations, especially decadal shifts that appear in historical records. This means the long-term trend is clear, but year-by-year predictions come with uncertainty.

Still, the models provide a useful framework. By understanding how different sources of mass change influence Earth’s spin, scientists can better anticipate the future and prepare for its impacts on navigation, mapping, and climate monitoring.

Drifting spin affects measurements

Polar motion may sound like a minor shift, but it affects real-world systems. Satellite navigation, deep space missions, and Earth observation tools all rely on precise coordinate systems.

As the rotation axis drifts, these systems must adjust. A wandering pole also causes subtle changes in Earth’s shape. These are called pole tides.

They can slightly deform the planet’s surface, especially in mid-latitude regions. The study estimates vertical deformations of up to 2.8 centimeters in some areas by 2100. Even gravity changes with the motion.

Shifts in mass and rotation create gravity variations that modern instruments can detect. These changes might help scientists learn more about processes deep within Earth, including mantle dynamics.

Climate change may control Earth’s rotation

Another key insight from the study is the growing dominance of climate effects over geological ones. Traditionally, processes like Glacial Isostatic Adjustment — where land slowly rebounds after ice melt — were thought to dominate long-term polar motion.

But under high-emission futures, climate-induced shifts may surpass geological ones. This suggests that modern climate trends will leave a clearer mark on Earth’s rotation than even ancient ice ages did.

These findings add urgency to climate policy. Reducing emissions could limit how much the pole shifts, preserving Earth’s rotational stability and reducing its cascading effects.

Changing spin tells a big story

This study offers more than a technical look at polar motion. It reveals the deep connections between surface climate and planetary physics.

As ice melts and water moves, Earth’s balance shifts — not just locally, but globally. From 1900 to 2100, our planet’s spin has been and will be reshaped by human activity.

Whether the pole drifts 12 meters or 27 meters depends on choices made in the coming decades. Either way, the axis is moving, and it is telling the story of a warming world.

The research by Shahvandi and Soja reminds us that no system on Earth is isolated. Climate touches everything – even the planet’s spin.

The study is published in the journal Geophysical Research Letters.

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