North Magnetic Pole
Encyclopedia
Earth's magnetic field
Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
points vertically downwards (i.e., the "dip" is 90°). Though geographically in the north, it is, by the direction of the magnetic field lines, physically the south pole of the Earth's magnetic field. The North Magnetic Pole should not be confused with the Geographic North Pole
North Pole
The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is, subject to the caveats explained below, defined as the point in the northern hemisphere where the Earth's axis of rotation meets its surface...
, nor with the lesser known North Geomagnetic Pole described later in this article.
The North Magnetic Pole moves slowly over time due to magnetic changes in the Earth's core. In 2001, it was determined by the Geological Survey of Canada to lie near Ellesmere Island
Ellesmere Island
Ellesmere Island is part of the Qikiqtaaluk Region of the Canadian territory of Nunavut. Lying within the Canadian Arctic Archipelago, it is considered part of the Queen Elizabeth Islands, with Cape Columbia being the most northerly point of land in Canada...
in northern Canada at 81.3°N 110.8°W. It was estimated to be at 82.7°N 114.4°W in 2005. In 2009, it was moving toward Russia at between 34 and 37 mi (55-60 km) per year.
Its southern hemisphere counterpart is the South Magnetic Pole
South Magnetic Pole
The Earth's South Magnetic Pole is the wandering point on the Earth's surface where the geomagnetic field lines are directed vertically upwards...
. Because the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's magnetic field is not exactly symmetrical, the North and South Magnetic Poles are not antipodal
Antipodes
In geography, the antipodes of any place on Earth is the point on the Earth's surface which is diametrically opposite to it. Two points that are antipodal to one another are connected by a straight line running through the centre of the Earth....
: a line drawn from one to the other does not pass through the geometric centre of the Earth.
The Earth's North and South Magnetic Poles are also known as Magnetic Dip Poles, with reference to the vertical "dip" of the magnetic field lines at those points.
Polarity
All magnetMagnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.A permanent magnet is an object...
s have two poles that are distinguished by the direction of the magnetic flux
Magnetic flux
Magnetic flux , is a measure of the amount of magnetic B field passing through a given surface . The SI unit of magnetic flux is the weber...
. In principle these poles could be named in any way; for example, as "+" and "−", or "A" and "B". However, based on the early use of magnets in compass
Compass
A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions – north, south, east, and west. Intermediate directions are also defined...
es they were named the "north pole" (or more explicitly "north-seeking pole"), "N", and the "south pole" (or "south-seeking pole"), "S", with the north pole being the pole that pointed north (i.e. the one attracted to the Earth's North Magnetic Pole). Because opposite poles attract, the Earth's North Magnetic Pole is therefore, by this definition, physically a magnetic field south pole. Conversely, the Earth's South Magnetic Pole is physically a magnetic field north pole.
History
In early times European navigators believed that compass needles were attracted either to a "magnetic mountain" or "magnetic island" somewhere in the far north (see Rupes NigraRupes Nigra
The Rupes Nigra , a phantom island, was believed to be a 33-mile-wide magnetic island of black rock located at the Magnetic North Pole or at the North Pole itself. It purportedly explained why all compasses point to this location...
), or to the Pole Star
Pole star
The term "Pole Star" usually refers to Polaris, which is the current northern pole star, also known as the North Star.In general, however, a pole star is a visible star, especially a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent...
. The idea that the Earth itself acts as a giant magnet was first proposed in 1600 by the English physician and natural philosopher William Gilbert. He was also the first to define the North Magnetic Pole as the point where the Earth's magnetic field points vertically downwards. This is the definition used nowadays, though it would be several hundred years before the nature of the Earth's magnetic field was understood properly.
Expeditions and measurements
Early
The first expedition to reach the North Magnetic Pole was led by James Clark RossJames Clark Ross
Sir James Clark Ross , was a British naval officer and explorer. He explored the Arctic with his uncle Sir John Ross and Sir William Parry, and later led his own expedition to Antarctica.-Arctic explorer:...
, who found it at Cape Adelaide on the Boothia Peninsula
Boothia Peninsula
Boothia Peninsula is a large peninsula in Nunavut's northern Canadian Arctic, south of Somerset Island. The northern part, Murchison Promontory, is the northernmost point of mainland Canada, and thus North America....
on June 1, 1831. Roald Amundsen
Roald Amundsen
Roald Engelbregt Gravning Amundsen was a Norwegian explorer of polar regions. He led the first Antarctic expedition to reach the South Pole between 1910 and 1912 and he was the first person to reach both the North and South Poles. He is also known as the first to traverse the Northwest Passage....
found the North Magnetic Pole in a slightly different location in 1903. The third observation was by Canadian government scientists Paul Serson and Jack Clark, of the Dominion Astrophysical Observatory
Dominion Astrophysical Observatory
The Dominion Astrophysical Observatory, located on Observatory Hill, in Saanich, British Columbia, was completed in 1918 by the Canadian government. Proposed and designed by John S...
, who found the pole at Allen Lake on Prince of Wales Island
Prince of Wales Island, Nunavut
One of the larger members of the Canadian Arctic Archipelago, Prince of Wales Island is an Arctic island in Nunavut, Canada, lying between Victoria Island and Somerset Island and south of the Queen Elizabeth Islands....
in 1947.
Modern (post 1996)
The Canadian government has made several measurements since, which show that the North Magnetic Pole is moving continually northwestward. In 1996 an expedition certified its location by magnetometerMagnetometer
A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...
and theodolite
Theodolite
A theodolite is a precision instrument for measuring angles in the horizontal and vertical planes. Theodolites are mainly used for surveying applications, and have been adapted for specialized purposes in fields like metrology and rocket launch technology...
at 78°35.7′N 104°11.9′W. Its estimated 2005 position was 82.7°N 114.4°W, to the west of Ellesmere Island
Ellesmere Island
Ellesmere Island is part of the Qikiqtaaluk Region of the Canadian territory of Nunavut. Lying within the Canadian Arctic Archipelago, it is considered part of the Queen Elizabeth Islands, with Cape Columbia being the most northerly point of land in Canada...
in Canada. During the 20th century it moved 1100 km, and since 1970 its rate of motion has accelerated from 9 km/year to approximately 41 km/year, or 1.3 mm/sec (2001–2003 average; see also Polar drift
Polar drift
Polar drift is a geological phenomenon caused by variations in the flow of molten iron in Earth's outer core, resulting in changes in the orientation of Earth's magnetic field, and hence the position of the magnetic north pole....
). If it maintained its present speed and direction it would reach Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
in about 50 years, but it is expected to veer from its present course and slow its rate of motion.
This general movement is in addition to a daily or diurnal variation in which the North Magnetic Pole describes a rough ellipse, with a maximum deviation of 80 km from its mean position. This effect is due to disturbances of the geomagnetic field by charged particle
Charged particle
In physics, a charged particle is a particle with an electric charge. It may be either a subatomic particle or an ion. A collection of charged particles, or even a gas containing a proportion of charged particles, is called a plasma, which is called the fourth state of matter because its...
s from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
.
| North Magnetic Pole | (2001) 81.3°N 110.8°W | (2004 est) 82.3°N 113.4°W | (2005 est) 82.7°N 114.4°W |
| South Magnetic Pole | (1998) 64.6°S 138.5°E. | (2004 est) 63.5°S 138.0°E |
The first team of novices to reach the Magnetic North Pole did so in 1996, led by David Hempleman-Adams. It included the first British woman and first Swedish woman to reach the Pole. The team also successfully tracked the location of the Magnetic North Pole on behalf of the University of Ottawa.
The biennial Polar Race
Polar Race
The Polar Race is a biennial race from Resolute, Nunavut in northern Canada to the Magnetic North Pole. Teams of two, three or four walk/ski 350 miles pulling their food and equipment on sleds. Although not unsupported, there are strict rules on the carrying of equipment, with only food, fuel and...
takes place between Resolute Bay
Resolute Bay
Resolute Bay is an Arctic waterway in Qikiqtaaluk Region, Nunavut, Canada. It is located in Parry Channel on the southern side of Cornwallis Island. The hamlet of Resolute is located on the northern shore of the bay and Resolute Bay Airport to the northwest...
in northern Canada and the 1996-certified location of the North Magnetic Pole at 78°35.7′N 104°11.9′W. On 25 July 2007, the Top Gear
Top Gear (current format)
Top Gear is a British television series about motor vehicles, primarily cars. It began in 1977 as a conventional motoring magazine show. Over time, and especially since a relaunch in 2002, it has developed a quirky, humorous style...
Polar Challenge Special
Top Gear: Polar Special
Top Gear: Polar Special was an episode of the popular series Top Gear, first broadcast on 25 July 2007 on BBC Two. It was an attempt by the BBC's Top Gear crew to be the first to drive a motor vehicle to the 1996 location of the Magnetic North Pole....
was broadcast on BBC Two
BBC Two
BBC Two is the second television channel operated by the British Broadcasting Corporation in the United Kingdom. It covers a wide range of subject matter, but tending towards more 'highbrow' programmes than the more mainstream and popular BBC One. Like the BBC's other domestic TV and radio...
in the United Kingdom, in which Jeremy Clarkson
Jeremy Clarkson
Jeremy Charles Robert Clarkson is an English broadcaster, journalist and writer who specialises in motoring. He is best known for his role on the BBC TV show Top Gear along with co-presenters Richard Hammond and James May...
and James May
James May
James Daniel May is an English television presenter, journalist and writer. He is best known for his role as co-presenter of the award-winning motoring programme Top Gear alongside Jeremy Clarkson and Richard Hammond....
became the first people in history to reach this location in a car.
Magnetic north and magnetic declination
Compass
A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions – north, south, east, and west. Intermediate directions are also defined...
needle points is known as magnetic north. In general, this is not exactly the direction of the North Magnetic Pole (or of any other consistent location). Instead, the compass aligns itself to the local geomagnetic field, which varies in a complex manner over the Earth's surface, as well as over time. The angular difference between magnetic north and true north (defined in reference to the Geographic North Pole), at any particular location on the Earth's surface, is called the magnetic declination
Magnetic declination
Magnetic declination is the angle between magnetic north and true north. The declination is positive when the magnetic north is east of true north. The term magnetic variation is a synonym, and is more often used in navigation...
. Most map coordinate systems are based on true north, and magnetic declination is often shown on map legends so that the direction of true north can be determined from north as indicated by a compass.
Magnetic declination has been measured in many countries, including the U.S. The line of zero declination (the agonic line) in the U.S. runs from the North Magnetic Pole through Lake Superior
Lake Superior
Lake Superior is the largest of the five traditionally-demarcated Great Lakes of North America. It is bounded to the north by the Canadian province of Ontario and the U.S. state of Minnesota, and to the south by the U.S. states of Wisconsin and Michigan. It is the largest freshwater lake in the...
and southward into the Gulf of Mexico. Along this line, true north is the same as magnetic north. West of the line of zero declination, a compass will give a reading that is east of true north. Conversely, east of the line of zero declination, a compass reading will be west of true north.
Magnetic declination is still very important for certain types of navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...
that have traditionally made much use of magnetic compass
Compass
A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions – north, south, east, and west. Intermediate directions are also defined...
es; see the main article (Magnetic declination
Magnetic declination
Magnetic declination is the angle between magnetic north and true north. The declination is positive when the magnetic north is east of true north. The term magnetic variation is a synonym, and is more often used in navigation...
) for details.
North Geomagnetic Pole
As a first-order approximationOrders of approximation
In science, engineering, and other quantitative disciplines, orders of approximation refer to formal or informal terms for how precise an approximation is, and to indicate progressively more refined approximations: in increasing order of precision, a zeroth order approximation, a first order...
, the Earth's magnetic field can be modelled as a simple dipole
Dipole
In physics, there are several kinds of dipoles:*An electric dipole is a separation of positive and negative charges. The simplest example of this is a pair of electric charges of equal magnitude but opposite sign, separated by some distance. A permanent electric dipole is called an electret.*A...
(like a bar magnet), tilted about 11° with respect to the Earth's rotation axis (which defines the Geographic North and Geographic South Poles) and centred at the Earth's centre. The North and South Geomagnetic Poles are the antipodal points where the axis of this theoretical dipole intersects the Earth's surface. If the Earth's magnetic field were a perfect dipole then the field line
Field line
A field line is a locus that is defined by a vector field and a starting location within the field. Field lines are useful for visualizing vector fields, which are otherwise hard to depict...
s would be vertical at the Geomagnetic Poles, and they would coincide with the Magnetic Poles. However, the approximation is imperfect, and so the Magnetic and Geomagnetic Poles lie some distance apart.
Like the North Magnetic Pole, the North Geomagnetic Pole attracts the north pole of a bar magnet
Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.A permanent magnet is an object...
and so is in a physical sense actually a south magnetic pole. It is the centre of the region of the magnetosphere
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...
in which the Aurora Borealis can be seen. As of 2005 it was located at approximately 79.74°N 71.78°W, off the northwest coast of Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
, but it is now drifting away from North America and toward Siberia.
Geomagnetic reversal
Over the life of the Earth, the orientation of Earth's magnetic field has reversed several times, with magnetic north becoming magnetic south and vice versa – an event known as a geomagnetic reversalGeomagnetic reversal
A geomagnetic reversal is a change in the Earth's magnetic field such that the positions of magnetic north and magnetic south are interchanged. The Earth's field has alternated between periods of normal polarity, in which the direction of the field was the same as the present direction, and reverse...
. Evidence of geomagnetic reversals can be seen at mid-ocean ridge
Mid-ocean ridge
A mid-ocean ridge is a general term for an underwater mountain system that consists of various mountain ranges , typically having a valley known as a rift running along its spine, formed by plate tectonics. This type of oceanic ridge is characteristic of what is known as an oceanic spreading...
s where tectonic plates move apart and the seabed is filled in with magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
. As the magma seeps out of the mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
the magnetic particles contained within it are oriented in the direction of the magnetic field at the time the magma cools and solidifies.
