South Magnetic Pole

South Magnetic Pole
NOAA · Public domain · source
Name	South Magnetic Pole
Discovered	1831
Discovered by	James Clark Ross
Region	Antarctic

South Magnetic Pole is the point on the surface of the Earth where the planet's geomagnetic field lines are directed vertically upward, marking one end of the geomagnetic dipole. The feature is distinct from the Geographic South Pole and is important for polar navigation, geomagnetic research, and historical exploration of Antarctica. Its position migrates over time due to processes in the Earth's core, and it has been the objective of expeditions from the United Kingdom, France, and United States.

Definition and Nature

The South Magnetic Pole is defined by the local verticality of the ambient magnetic field as measured by a magnetic dipole indicator such as a dip circle or a magnetometer; it is the locus where the magnetic inclination equals +90° relative to the local horizontal. Instruments used historically include devices from James Clark Ross's era and modern fluxgate magnetometers supplied by institutions like the British Antarctic Survey and the U.S. Geological Survey. The concept is related to the theoretical Geomagnetic poles of a best-fit axial dipole, distinct from the observational instantaneous magnetic pole used in field surveys by teams from CSIRO and the National Oceanic and Atmospheric Administration.

Historical Discovery and Exploration

The first recorded identification of the pole was during the 19th century when James Clark Ross located a position near the pole during the Ross expedition (1839–1843), using instruments comparable to those used in the Great Trigonometrical Survey era. Subsequent visits and improved determinations came from expeditions by figures associated with Roald Amundsen, Robert Falcon Scott, and scientific teams from the Scottish National Antarctic Expedition and the Belgian Antarctic Expedition (1897–1899). In the 20th century, surveys by the British Antarctic Survey, United States Antarctic Program, and the Soviet Antarctic Expedition refined locations; later airborne and satellite missions by NASA, European Space Agency, and CNES provided global magnetometer coverage. The historical record intersects with developments in navigation used by explorers such as Ernest Shackleton and cartographers from the Royal Geographical Society.

Location, Movement, and Measurement

The instantaneous position of the pole has been mapped repeatedly by magnetic surveys and by global geomagnetic models such as the International Geomagnetic Reference Field and the World Magnetic Model. Measurements combine land surveys from stations like Mawson Station with aeromagnetic data collected by aircraft from Lambert Glacier Region sorties and satellite magnetometry from missions like Ørsted (satellite), CHAMP, and Swarm (ESA mission). The pole moves due to secular variation driven by core flows; its drift has been documented by teams at Scripps Institution of Oceanography, Geoscience Australia, and the National Centres for Environmental Information. Reported positions often reference geographic features such as the Ross Ice Shelf and latitudes tied to the Antarctic Treaty area, with published coordinates updated in datasets curated by the British Antarctic Survey and the World Data Center for Geomagnetism.

Geophysical Causes and Core Dynamics

Variations in the pole’s location arise from fluid dynamics in the Earth's outer core, where turbulent convection of an iron-nickel alloy interacts with the Coriolis force and produces a geodynamo effect described by magnetohydrodynamics. Researchers from institutions such as Princeton University, University of Oxford, Caltech, and ETH Zurich model core flows with numerical codes informed by seismological constraints from groups at Incorporated Research Institutions for Seismology and IRIS. Paleomagnetic records studied by teams at Lamont–Doherty Earth Observatory and Utrecht University show field reversals and excursions recorded in basalt and sediment strata, connecting long-term pole behaviour to processes explored in projects funded by the National Science Foundation and the European Research Council.

Effects on Navigation and Wildlife

Shifts in the magnetic pole affect compass-based navigation used historically by mariners from the British East India Company era and later by modern crews aboard vessels registered in Panama and Norway. Aviation navigation systems and polar flights operated by carriers like Qantas, Air New Zealand, and LanChile must account for magnetic variation updated via products from the International Civil Aviation Organization and the World Magnetic Model maintained by NOAA and BGS. Wildlife such as migratory Adélie penguin populations studied by ecologists at the Australian Antarctic Division and the Polar Institute exhibit magnetoreception behaviors examined in comparative studies by researchers at University of Oslo, Max Planck Institute for Ornithology, and University of Tokyo; other species like loggerhead sea turtle and homing pigeon have been subjects in magnetoreception experiments at the Smithsonian Institution and Monash University.

Scientific Research and Monitoring

Ongoing monitoring integrates satellite missions like Swarm (ESA mission) and ground observatories coordinated through the International Real-time Magnetic Observatory Network and the INTERMAGNET program. Laboratories at University of Leeds, Imperial College London, University of Colorado Boulder, and GFZ German Research Centre for Geosciences analyze secular variation and rapid geomagnetic jerks, while computational efforts at NASA Goddard Space Flight Center and NCAR produce predictive models used by navigation authorities and researchers involved with the Polar Geospatial Center. Interdisciplinary projects bring together polar ecologists from Woods Hole Oceanographic Institution, geomagnetists from University of Toronto, and climate scientists from CSIRO to examine connections between geomagnetic variability, solar activity monitored by NOAA Space Weather Prediction Center, and implications for polar infrastructure managed under frameworks established by the Antarctic Treaty System.

Category:Antarctica Category:Geomagnetism Category:Polar exploration