The Magnetic North Pole
During the sixteenth century, mariners believed that somewhere in the North was a magnetic mountain that was the source of attraction for their compasses. Sir William Gilbert, physician to Queen Elizabeth I, suggested that the Earth itself was a giant magnet and that the force that directed the compass originated inside the Earth. Using a model of the Earth made from lodestone (a naturally occurring magnetic rock), he also showed that there should be two points on the Earth where a magnetized needle would stand vertically — the North and South Magnetic Poles.
Initially, people believed that the North Magnetic Pole coincided with the north geographic pole. Magnetic observations made by explorers in subsequent decades showed that this was not true, and by the early nineteenth century, the accumulated observations proved that the magnetic pole must be somewhere in Arctic Canada.
In 1831, at Cape Adelaide on the west coast of Boothia Peninsula, James Clark Ross measured a dip of 89 degrees 59 minutes. For all practical purposes, he had reached the North Magnetic Pole.
The next attempt to reach the North Magnetic Pole was made some 70 years later by the Norwegian explorer Roald Amundsen. In 1903, he left Norway on his famous voyage through the Northwest Passage. His primary goal was to set up a temporary magnetic observatory in the Arctic and to relocate the North Magnetic Pole.
A pole position was next determined by Canadian government scientists shortly after World War II. Paul Serson and Jack Clark, of the Dominion Observatory, measured a dip of 89 degrees 56 minutes at Allen Lake on Prince of Wales Island. This, in conjunction with other observations made in the vicinity, showed that the pole had moved some 250 kilometers northwest since the time of Amundsen's observations.
Observations by Canadian government scientists in 1962, 1973, 1984, and most recently in 1994, showed that the general northwesterly movement of the pole is continuing, and that during this century it has moved on average 10 kilometers per year.
It is important to realize that when we talk about the location of the pole, we are referring to an average position. The pole wanders daily in a roughly elliptical path around this average position, and may frequently be as much as 80 kilometers away from this position when the Earth's magnetic field is disturbed.
We now know that the cause of the Earth's magnetic field is much more complex; we believe that it is produced by electrical currents that originate in the hot, liquid, outer core of the Earth. As a simple analogy, consider an electromagnet, in which we can produce a strong magnetic field by passing an electric current through a coil of wire.
The position of the North Magnetic Pole is strongly influenced by the natural conditions variation in its vicinity. For example, if the dip is 90 degrees at a given point this year, that point will be the North Magnetic Pole, by definition. However, because of secular variation, the dip at that point will change to 89 degrees 58 minutes in about two years, so it will no longer be the pole. However, at some nearby point, the dip will have increased to 90 degrees, and that point will have become the pole. In this manner, the pole slowly moves across the Arctic.
In April and May of 1994, Larry Newitt of the Geological Survey of Canada and Charles Barton of the Australian Geological Survey Organization conducted a survey to determine the average position of the North Magnetic Pole at that time. Working out of Resolute Bay, Northwest Territories, they established a temporary magnetic observatory on Lougheed Island, close to the predicted position of the pole. This allowed them to monitor the short-term fluctuations of the magnetic field that result in the daily motion of the pole.
In addition, the strength and direction of the magnetic field were measured at this site, and at seven additional sites in the region. From these observations, the point at which the average dip was 90 degrees could be determined.
They determined that the average position of the North Magnetic Pole in 1994 was located on the Noice Peninsula, southwest Ellef Ringnes Island, at 78.3 degrees North, 104.0 minutes West. The yearly motion of the pole has increased, and is now 15 kilometers per year.
The reasons that the pole generates so much interest have changed over the years. For Ross, the search for the pole was a byproduct of scientific nationalism. For Amundsen, it offered a good excuse to sail through the Northwest Passage. Today, we are interested in the pole as a tool for magnetic cartography.
Additional Resources:For further information or questions about the Magnetic North Pole, you can contact:
Geological Survey of Canada
Natural Resources Canada
1 Observatory Crescent
Ottawa, Ontario K1A 0Y3