Earth’s rotational axis is not fixed in place. It wanders continuously, and human activities have measurably altered that wandering over the past few decades. The axis drifts through Earth’s crust at roughly ten centimeters per year on average, driven by a mix of processes ranging from the slow rebound of continents after the last ice age to the redistribution of water across the planet’s surface. Since the 1990s, that drift changed direction in ways researchers have tied directly to melting polar ice and massive groundwater extraction. The shift is tiny in human terms, but it is real, detectable, and accelerating in ways that matter for precision navigation and timekeeping.
What “Axis Movement” Actually Means
When scientists talk about the Earth’s axis moving, they usually mean polar motion: the spin axis shifting its position relative to the solid body of the planet. Picture a spinning top that does not spin perfectly upright. Earth’s spin axis traces a small, irregular path around the geographic poles. Over the twentieth century, the average position of that spin axis drifted toward Labrador, Canada, at a speed of about 10.5 centimeters per year.1Elsevier (Earth and Planetary Science Letters). What drives 20th century polar motion? That is not a tilt getting steeper or shallower in the way you might imagine a globe leaning over. It is the point where the axis intersects Earth’s surface slowly sliding around.
This is separate from the obliquity, which is the angle of Earth’s axis relative to its orbit around the Sun (currently about 23.4 degrees). Obliquity changes too, but on timescales of tens of thousands of years. The shorter-term polar drift that makes headlines is a different phenomenon, and the two are driven by completely different forces.
The 1990s Direction Change
For most of the twentieth century, Earth’s spin axis drifted along a fairly steady path. Then, in the mid-1990s, the direction of that drift shifted noticeably. Researchers studying satellite gravity data confirmed this change and traced its cause to shifts in terrestrial water storage, meaning the total amount of water locked up in ice sheets, aquifers, lakes, and soil around the world.2Geophysical Research Letters. Polar Drift in the 1990s Explained by Terrestrial Water Storage Changes When large masses of water move from one part of the planet to another, the distribution of Earth’s mass changes, and the spin axis adjusts in response, the same way a figure skater’s spin changes when they shift their arms.
The data from satellite missions showed that water storage losses from polar regions, combined with contributions from other areas, pushed the axis drift toward a direction of about 26 degrees east longitude at a rate of a few milliarcseconds per year.3Geological Society of India. Earth’s Axial Tilt: The Specifics – Section: Earth Axis Tilt due to Climate Change That trend appeared to accelerate further around 2005 to 2006.4PubMed Central. Drift of the Earth’s Principal Axes of Inertia from GRACE and Satellite Laser Ranging Data – Section: Results To be clear, these are extraordinarily small shifts by everyday standards. A milliarcsecond corresponds to about three centimeters on Earth’s surface. But in geophysics and precision navigation, these shifts are significant and trackable.
How Water Redistribution Drives the Drift
A 2024 study in Nature Geoscience broke down the contributions to polar motion from different sources: the deep interior of the planet (core and mantle), and surface processes like ice melting and changes in water storage. The surface mass redistribution turned out to produce a relatively weak long-term trend, but it explained about 90 percent of the year-to-year and multi-decade variations in polar motion throughout the twentieth century.5Nature Geoscience. Contributions of core, mantle and climatological processes to Earth’s polar motion – Section: Results The dominant driver of those surface-level changes was terrestrial water storage, tied to global shifts between wetter and drier conditions driven by various climate patterns.
Two human activities have contributed measurably. First, groundwater pumping: humanity has extracted enormous volumes of water from underground aquifers, particularly for irrigation, and that water eventually reaches the ocean. This redistribution of mass is large enough to influence polar drift.6PubMed. Rampant groundwater pumping has changed the tilt of Earth’s axis Second, the filling of large reservoirs behind dams since the 1950s has moved water mass to new locations. An analysis of 88 major reservoirs found that while each one individually produces an effect far smaller than natural geophysical signals, the cumulative impact is not negligible and has contributed a meaningful fraction to the total observed polar drift over recent decades.7Geophysical Research Letters. Anthropogenic impact on global geodynamics due to reservoir water impoundment
Polar ice loss from Greenland and Antarctica adds to this picture. As ice melts from polar regions and that water spreads toward the equator, it moves mass away from the poles, which also slows Earth’s rotation slightly and nudges the spin axis.8Nature. Climate change has slowed Earth’s rotation — and could affect how we keep time
The Ice Age Hangover
Not all polar drift comes from recent water redistribution. A large part of the twentieth-century drift toward Canada has been attributed to glacial isostatic adjustment: the slow rebound of Earth’s crust and mantle after the enormous ice sheets of the last ice age melted away thousands of years ago. Those ice sheets, kilometers thick in places, pressed down on North America and Northern Europe. When the ice disappeared, the mantle began flowing back and the crust started rising. That process is still happening and will continue for thousands of years more.
Researchers have used the observed long-term drift of the rotation axis, along with changes in the length of day and in Earth’s gravity field, as evidence of this ongoing rebound and as a tool for understanding the viscosity of Earth’s deep mantle.9Advances in Space Research. Secular changes in rotation and gravity: Evidence of post-glacial rebound or of changes in polar ice? One analysis estimated that glacial rebound accounts for only about a third of the total observed polar motion over the twentieth century.1Elsevier (Earth and Planetary Science Letters). What drives 20th century polar motion? The remainder comes from convective flow in the mantle and from surface water redistribution. More refined models of the rebound have used polar motion data to estimate the viscosity of the deepest regions of the lower mantle, below about 1,400 kilometers depth, where other geological observations cannot reach.10Journal of Geophysical Research: Solid Earth. Glacial isostatic adjustment and Earth rotation: Refined constraints on the viscosity of the deepest mantle
Short-Term Wobbles
On top of the slow multi-decade drift, Earth’s axis wobbles on much shorter timescales. The best known of these is the Chandler wobble, a roughly 14-month oscillation of the spin axis that was discovered in the 1890s. The axis traces a small circle, just a few meters across at the pole, over this period. For a long time, what kept the Chandler wobble going was a mystery, since friction inside the Earth should damp it out within decades if nothing were feeding energy into it.
Studies using atmospheric and oceanic data have shown that wind patterns, barometric pressure changes, and ocean circulation provide enough energy at the right frequency to sustain the Chandler wobble.11Journal of Geophysical Research: Solid Earth. Atmospheric and oceanic contributions to Chandler wobble excitation determined by wavelet filtering Atmospheric winds and pressure variations alone maintain a large portion of it, with the wind contribution and the pressure contribution complementing each other over time.12Journal of Geophysical Research: Solid Earth. Atmospheric excitation of the Chandler wobble, 1983–1998
There are also seasonal signals. The jet streams in both hemispheres change strength with the seasons, which shifts atmospheric angular momentum and produces a clear annual signal in Earth’s rotation. The Northern Hemisphere’s seasonal changes are the larger of the two.13Journal of Geophysical Research: Oceans. Variations in atmospheric angular momentum on global and regional scales and the length of day These short-term variations are well matched by models that combine atmospheric, oceanic, and hydrological contributions, particularly at seasonal and sub-seasonal timescales.14Geophysical Research Letters. Low degree gravitational changes from earth rotation and geophysical models
Do Earthquakes Shift the Axis?
After major earthquakes, news reports often claim that the event shifted Earth’s axis by some number of centimeters. This is technically true but deeply misleading in scale. Calculations using data from over 2,000 earthquakes between 1977 and 1985 found that earthquake-induced changes to Earth’s rotation were generally about a hundred times smaller than the observed changes from other sources.15Geophysical Journal International. Changes in the Earth’s rotation and low-degree gravitational field induced by earthquakes – Section: Summary Earthquakes do tend to push the rotational pole in a preferred direction and to make the Earth slightly more spherical by pulling mass toward its center, but these effects are tiny compared to the water redistribution and mantle rebound processes described earlier.
A more recent analysis covering global major earthquakes from 1976 to 2019 confirmed that the cumulative energy they contribute to polar motion amounts to a minuscule 0.01 megawatts.16Geophysical Journal International. Coseismic changes in the kinetic rotational energy of the Earth from 1976 to 2019 For context, a single household appliance draws more power. So while a magnitude 9 earthquake can produce a measurable blip in the spin axis position, earthquakes are not a meaningful driver of the longer-term drift that geophysicists are concerned about.
Magnetic Poles and the Rotational Axis Are Not the Same Thing
One persistent source of confusion is the difference between Earth’s magnetic poles and its rotational axis. The magnetic north pole has been moving rapidly, accelerating noticeably during the 1990s as it headed from the Canadian Arctic toward Siberia. This acceleration has been linked to changes in the flow of liquid iron in Earth’s outer core, specifically involving magnetic field structures beneath the New Siberian Islands.17Journal of Geophysical Research: Solid Earth. Magnetic flux expulsion from the core as a possible cause of the unusually large acceleration of the north magnetic pole during the 1990s
The magnetic poles and the rotational axis are driven by completely different physical processes. Magnetic poles respond to the churning of iron in Earth’s liquid outer core, while rotational axis drift responds to mass redistribution across the planet. The north and south magnetic poles do not even move symmetrically; they change independently because of the asymmetric complexity of Earth’s magnetic field in each hemisphere, and their movements are not correlated with changes in the rotational axis.18Earth, Planets and Space. Magnetic poles and dipole tilt variation over the past decades to millennia When someone asks “Is the Earth tilting more?” they could be thinking of either phenomenon, but the two are unrelated.
The Very Long View
Zoom out far enough and the axis changes in more dramatic ways. On timescales of tens of thousands of years, Earth’s obliquity, that 23.4-degree tilt responsible for our seasons, oscillates between about 22.1 and 24.5 degrees in a cycle of roughly 41,000 years. This is one of the Milankovitch cycles that pace ice ages. The timing of this cycle depends on gravitational interactions with other planets, particularly Mars. Simulations have shown that if Mars were substantially more massive, Earth’s obliquity cycle would lengthen and shift to a different frequency band.19Publications of the Astronomical Society of the Pacific. The Dependence of Earth Milankovitch Cycles on Martian Mass This is a thought exercise more than a practical concern, but it underlines how Earth’s tilt stability depends on the arrangement of our whole solar system.
On even longer timescales, the planet undergoes true polar wander: a wholesale reorientation of the entire solid Earth relative to the spin axis, driven by enormous mass anomalies in the mantle. Supercontinents leave imprints on mantle convection patterns that persist for hundreds of millions of years after the continents themselves break apart. The current shape of Earth’s gravity field may still carry a legacy from the ancient supercontinent Pangea and its surrounding subduction zones.20Journal of Geophysical Research: Planets. Long‐term rotation and mantle dynamics of the Earth, Mars, and Venus Mars, lacking plate tectonics, experiences true polar wander driven instead by the weight of massive volcanic regions like the Tharsis bulge rather than by subduction.
Why Tracking Axis Movement Matters in Practice
Precision that sounds absurd in everyday life turns out to be essential for modern technology. The International Earth Rotation Service monitors Earth’s orientation using networks of radio telescopes (very long baseline interferometry), satellite laser ranging, and GPS stations. The measurements reach the milliarcsecond level, equivalent to a few centimeters on Earth’s surface.21GPS Solutions. Evaluation of earth rotation parameters from modernized GNSS navigation messages These Earth rotation parameters are needed every time you convert between a coordinate system fixed to the Earth’s surface and one fixed to the stars, which happens constantly in satellite navigation, spacecraft guidance, and precise surveying.
Climate change has introduced new complications. As polar ice melts and redistributes mass toward the equator, it slows Earth’s rotation slightly. A study projecting atmospheric changes through the twenty-first century under a high-emissions scenario found that shifting wind patterns could add an atmosphere-driven slowdown equivalent to about a 0.43-millisecond increase in the length of day per century, roughly one-fifth the slowdown already caused by tidal friction from the Moon.22Journal of Geophysical Research: Atmospheres. Atmospheric Excitation of Length of Day Inferred From 21st Century Climate Projections Fractions of a millisecond sound trivial, but they accumulate, and the systems that coordinate satellite signals, financial transactions, and power grids all depend on precise timekeeping that accounts for Earth’s actual rotation speed.
One concrete consequence that was debated recently: the melting of polar ice may have delayed the need for the first-ever “negative leap second.” Atomic clocks tick at a constant rate, but Earth’s rotation speeds up and slows down. Since 1972, leap seconds have been periodically added to keep clock time aligned with the planet. If Earth’s core-driven acceleration had continued unchecked, timekeepers might have needed to subtract a second for the first time, but ice-sheet melting slowed the planet’s spin enough to push that event further into the future. The interplay between deep-Earth processes and surface ice loss is now a real factor in how we keep time.
How Scientists Actually Detect These Changes
None of this would be knowable without space geodesy. The GRACE satellite missions (launched in 2002 and succeeded by GRACE-Follow On in 2018) measure tiny variations in Earth’s gravitational field by tracking the distance between a pair of co-orbiting satellites with micrometer precision. When one satellite passes over a region with slightly more mass, it speeds up relative to its partner. From those fluctuations, scientists build monthly maps of how mass is shifting around the planet: ice sheets thinning, aquifers depleting, ocean water redistributing. These gravity maps are the backbone of the research linking water storage changes to polar drift.
Satellite laser ranging, where observatories on the ground bounce laser pulses off reflectors on orbiting satellites and measure the round-trip time, provides an independent check. Very long baseline interferometry, which uses radio telescopes spread across continents to observe quasars billions of light-years away, pins down Earth’s orientation in space with extraordinary precision. Together, these techniques have transformed polar motion from a curiosity tracked by a handful of observatories into a continuously monitored quantity with implications for everything from climate science to the definition of a second.