See also: Introduction

The change in velocity of the North Magnetic Pole since the early 1970s has been remarkable – 9 km/yr to 41 km/yr. This is clearly seen in the accompanying plot which shows the average rate of motion between observations as a function of time. The acceleration has also increased from 0.22 km/yr² to 2.21 km/yr². A change in the velocity of the North Magnetic Pole must be reflected in a corresponding change in both the inclination and the horizontal component of the magnetic field (H). Data from Resolute Bay Observatory, the nearest to the North Magnetic Pole, show that the annual change in H has increased from roughly -10 nT/yr to almost 70 nT/yr during the past half century (top panel of diagram). The increase has not been uniform, but as a series of steps that have occurred in approximately 1970, 1979 and 1990.

Changes in the magnetic field characterized by an abrupt change in the secular variation have been named "(geo)magnetic jerks" or "geomagnetic impulses". Six jerks of global extent have occurred during the past century: in 1901, 1913, 1925, 1969, 1978 and 1992. The last three jerks can be seen clearly as abrupt changes in the slope of the annual change in H at Resolute Bay. The 1969 jerk corresponds to the start of the increase in the speed of the NMP and the two subsequent jerks, especially that near 1992, appear to correlate with additional increases in the speed.

In contrast to its present-day acceleration, the Magnetic Pole showed little apparent motion between 1831 and 1904. It seems highly unlikely that the Pole actually remained stationary for 73 years, but there are no direct observations from which we can determine its motion during that time period. However, we can use spherical harmonic models produced for this time period to infer the track of the North Magnetic Pole. The accompanying plot shows North Magnetic Pole positions at 20 year intervals between 1820 and 1920 calculated from the spherical harmonic models produced by Jackson and colleagues. The model positions are slightly displaced to the north-west of the observed positions. If we adjust the track to best match the observed positions we find that the Magnetic Pole reached its southernmost latitude, 68.8°, in 1860. The year is significant since 1860 is the year of a possible magnetic jerk.

Spherical harmonic models can also be used to estimate the position of the North Magnetic Pole back to approximately 1600. Prior to that time there were too few observations from which reliable models can be produced. It appears that the North Magnetic Pole moved southeast a distance of approximately 860 km between 1760 to 1860. Prior to that is was located in a relatively confined area near 75° N, 110° W.