Why Magnetic North Moves

The Magnetic North Pole is one of the four senses of “north pole” covered in the /learn/the-north-pole support; the /learn/magnetic-north-vs-true-north support covers the operational conversion that matters because the magnetic and geographic poles are now nearly 1,000 km apart. This article focuses on the movement — why the magnetic pole drifts at all, why the drift accelerated in the late 20th century, what the 2019 emergency update to the World Magnetic Model was about, and what the geomagnetic-reversal record tells us about the long-term behaviour of the field.

The geodynamo

The geomagnetic field is generated by the geodynamo — the self-sustaining electromagnetic process that operates in Earth's outer core. The outer core is a ~2,260 km thick shell of molten iron and nickel between the solid inner core at depth ~5,150 km and the solid mantle at depth ~2,890 km. The fluid is hot, electrically conducting, and in continuous motion driven by three forces:

1. Thermal convection — heat from the inner core escapes outward through the outer core; warm fluid rises and cool fluid sinks.
2. Compositional convection — as the inner core slowly grows by crystallisation, lighter elements (sulphur, oxygen, silicon) are excluded from the solid and rise through the outer core, driving additional convection.
3. Coriolis force — Earth's rotation organises the convective motion into roughly columnar structures aligned with the rotation axis.

A moving electrically conducting fluid generates magnetic fields by electromagnetic induction (Faraday's law), and the geometry of the convection produces a field that is predominantly dipolar (a “bar magnet” aligned roughly with the rotation axis) with substantial non-dipolar components. About 90% of the field's energy is in the dipolar component; the remaining 10% is distributed across higher-order spherical harmonics. The /learn/the-earth-as-a-magnet support covers the geodynamo in more depth.

The Magnetic North Pole — the point on the surface where the field vector is vertical pointing inward — moves because the underlying convection pattern moves. The fluid is turbulent over decadal timescales, with concentrations of magnetic flux migrating across the core's surface and re-organising the field above. The pole's position is a sensitive indicator of these slow, deep changes.

The drift record

The Magnetic North Pole was first located in 1831 by James Clark Ross, a British Royal Navy officer on the second John Ross expedition in search of the Northwest Passage. Ross located the pole on 1 June 1831 at Cape Adelaide on the Boothia Peninsula in the Canadian Arctic (approximately 70°05′N, 96°47′W).

The pole remained in the Canadian Arctic for the next 160 years, drifting slowly northwest at about 10 km/year through the 19th and early 20th centuries. Around 1990, the drift accelerated and shifted direction toward the Arctic Ocean. Per NOAA NCEI World Magnetic Model records:

| Epoch | Approximate position | Drift rate | |---|---|---| | 1831 | 70.1°N, 96.8°W (Boothia Peninsula) | — | | 1900 | ~70.5°N, 96°W | ~10 km/year | | 1950 | ~74°N, 100°W | ~10 km/year | | 1990 | ~79°N, 105°W (near Ellesmere Island) | ~15 km/year | | 2000 | ~81°N, 110°W | ~40 km/year | | 2015 | ~86°N, 159°W | ~55 km/year | | 2020 | ~86°N, 165°E (crossed antimeridian ~2017) | ~50 km/year | | 2025 | ~86°N, 142°E | ~30 km/year |

The acceleration from the 1990s through 2015 was the most rapid change in pole position in the historical record. Since 2019 the drift has been slowing somewhat; current trajectory continues generally toward Russia, with the pole now closer to the geographic North Pole than at any time since precise measurements began.

The acceleration is interpreted as the result of an “in-and-out tug of war” between two regions of intense flux beneath northern Canada and Siberia. From the 1990s onward the Siberian patch grew while the Canadian one weakened, pulling the surface pole position toward Russia.

The 2019 emergency WMM update

The World Magnetic Model is the standard reference for the geomagnetic field used by every GPS device, every smartphone compass, every aviation chart, and every NATO/ICAO/IHO operational system. NOAA and the British Geological Survey jointly produce it on a 5-year cycle. The 2015 release covered 2015–2020; the model included a secular-variation prediction that linearly extrapolated the rate of change observed at the 2015 epoch.

By 2018, the prediction had drifted noticeably from reality. The Magnetic North Pole had moved faster than the WMM 2015 secular variation forecast, particularly across the Arctic. For most users the error was small — declination at typical mid-latitude locations remained accurate — but for aviation in the Arctic and military operations near the pole, the error was material. In February 2019 NOAA and BGS released an out-of-cycle WMM update; the new model used data through late 2018 to re-fit the secular variation.

The 2019 update was the first emergency WMM release in the model's history. The next regular release, WMM 2025, was issued on schedule in December 2024 with the rapid drift now accounted for. Subsequent updates are expected every 5 years; whether another out-of-cycle update will be needed depends on whether the field continues to behave non-linearly.

Modelling the field

Several distinct modelling apparatus exists for the geomagnetic field and its changes:

• World Magnetic Model (WMM) — NOAA/BGS joint product on a 5-year cycle, mandated by the US Department of Defense, the UK Ministry of Defence, NATO, and the IHO. Spherical-harmonic expansion to degree 12; ~340 coefficients. The /learn/the-world-magnetic-model support covers the model in detail.
• International Geomagnetic Reference Field (IGRF) — the IAGA consensus model, also released on a 5-year cycle (current IGRF-14, issued late 2024). IGRF goes to degree 13 and is the scientific reference model; WMM is the operational one.
• CHAOS — a higher-order scientific model produced by DTU Space using ground observatory and satellite data, updated more frequently. Used in research where WMM's lag matters.
• Other regional models — e.g. the British Geological Survey's models for the UK, the USGS's North American models.

Inputs to all these models come from:

• Ground observatories — the global INTERMAGNET network of ~150 stations measures the local field continuously and publishes vector readings every second.
• Satellites — the ESA Swarm constellation (three satellites launched in 2013, still operating in 2026) provides continuous global field measurements at altitude. Predecessors include MagSat (1979), Ørsted (1999), and CHAMP (2000–2010).
• Historical records — declination observations from ship logbooks, magnetic-survey records, and lava-flow paleomagnetism extend the record backward.

Field weakening and the South Atlantic Anomaly

Two longer-term observations are commonly cited in connection with magnetic-pole behaviour:

Field weakening. The dipole moment of Earth's magnetic field has decreased by roughly 5% per century since the first global field surveys around 1840. The current rate is about 0.5%/year, or about 6.5% per century. Whether this trend continues, accelerates, or reverses is unknown.

The South Atlantic Anomaly (SAA). A region of unusually weak geomagnetic field centred off the coast of Brazil, currently extending across the South Atlantic and South America. The field at the SAA's centre is about half the global average; the anomaly is growing in size and intensity per ESA Swarm data, particularly with a second lobe emerging over southern Africa. Satellites passing through the SAA experience higher charged-particle flux; the International Space Station crosses it several times per day and astronauts sometimes report visual phosphenes during transit.

The relationship between the SAA, the field weakening, and the possibility of a geomagnetic reversal is an active research area. The field has weakened before (e.g. during the Laschamp excursion ~41,000 years ago) without a full reversal occurring.

Geomagnetic reversals

The geomagnetic field reverses polarity episodically. The paleomagnetic record — fossilised field orientations frozen into basaltic rocks at mid-ocean ridges and in volcanic flows — documents roughly 170 full reversals over the past 80 million years.

The most recent full reversal is the Brunhes-Matuyama transition, about 780,000 years ago. The Brunhes Chron (the current period of “normal” polarity) has thus lasted about 780 kyr; the Matuyama Chron before it lasted about 1.79 Myr; reversal-free intervals have lasted from tens of thousands of years to roughly 40 million years (the “Cretaceous Quiet Zone”).

A reversal is not instantaneous. Geological evidence suggests transitions take 1,000–10,000 years, during which the field weakens, becomes multi-polar, and finally re-establishes in the opposite polarity. There is no obvious effect on biological life from past reversals; the field protects against cosmic radiation but does not vanish entirely during transitions.

Whether the current weakening and the accelerated pole drift indicate that another reversal is approaching is not known. The current weakening could equally precede a slow recovery. The next 50–100 years of observation will sharpen the picture; for now, the operational consequence is that the WMM continues to publish updates on a 5-year cycle, with the option of out-of-cycle updates like the 2019 release if the field shifts faster than the model predicts.

Practical consequences

The Magnetic North Pole's drift has direct operational consequences:

• Aviation runway renaming. Runways are numbered by magnetic heading divided by 10. As declination changes, the magnetic heading of a fixed runway drifts. When the change exceeds about 3°, ICAO practice triggers a renumbering. The /learn/aviation-runway-numbering support covers the process; recent examples include Tampa International (18R/L → 19R/L in 2011), Fairbanks (2008), and several smaller airports across Alaska as the magnetic field shifted faster than the surveying schedule.
• Marine compass adjustment. Ship compasses are calibrated for local declination; the adjustment shifts with the field. Charts print declination and the annual rate of change; navigators are expected to update for elapsed time since the chart was issued.
• Smartphone-based heading. Every smartphone uses the current WMM to convert raw magnetometer readings into compass-true heading. The WMM 2019 emergency update was distributed via OS updates so devices could correctly report compass bearings in the rapidly-changing field.
• Hiking compasses with adjustable declination. Older compasses without adjustable bezels are now mis-set for many parts of the world where declination has shifted by several degrees over the past few decades.

The 2016 Swarm-derived discovery of a high-speed jet of liquid iron flowing beneath Canada and Siberia provided the first direct observational basis for the rapid drift. The jet, about 420 km wide and flowing at roughly 40 km/year, is the strongest core-fluid motion yet measured.

Sources

• NOAA NCEI, World Magnetic Model — current WMM 2025 and history.
• IAGA, International Geomagnetic Reference Field — IGRF-14 and the modelling consensus.
• USGS Geomagnetism Program — North American observatories and modelling.
• ESA Swarm — satellite-derived field observations and the SAA.
• British Geological Survey, Geomagnetism — UK geomagnetic services and the WMM partnership.

For closely related topics, see /learn/the-world-magnetic-model for the modelling apparatus, /learn/magnetic-declination-explained for the field-direction angle this article's drift produces, and /learn/the-north-pole for the geographic counterpart that this article is not about.