Polar Plumes cause magnetic North to drift

While the world had its eyes on OJ Simpson and Michael Jackson, a rare natural phenomenon was occurring. During the 1990’s the North magnetic pole began moving faster. In fact, its drift speed increased from 15km/yr to 55km/yr by the decade’s end.
Observations of the magnetic pole’s motion began soon after its discovery in the early 19th century. James Clark Ross first measured the magnetic North pole on a British expedition in search of the Northwest Passage. (He apparently fixed the British flag on the spot and “took possession of the North magnetic pole and its adjoining territory” for his nation.) Several decades later, another measurement was taken that deviated roughly 50km from the first observation. Natural Resources Canada began taking regular measurements in 1948 in order to monitor the NMP’s motion. Today, low-Earth orbiting satellites carrying high-precision magnetometers measure the movement of magnetic North with an unprecedented level of spatial and temporal resolution.
Magnetic recordings from polar cap observatories in Greenland and the high Canadian Arctic are now revealing that the secular variation in magnetic field strength has also experienced a large increase over the 1990 interval. In short, the magnetic pole has not only become faster, but more erratic. Furthermore, it seems that these two phenomena covary- secular variation is responsible for as much as 75% of the increase in drift speed.
What has caused the recent dramatic shift in magnetic pole variability? Scientists are now speculating that NMP drift may be direct result of a hidden plume rising within the Earth’s core, somewhere deep beneath the Arctic. This hypothesis, termed the “core plume hypothesis” may reveal important information about the physics of the earth’s core, which scientists can only study through indirect measurement.
Regions of low-density fluid sometimes form near the boundary between the inner and outer core. This fluid rises in plumes that writhe and twist into spirals due to the rapid rotation of the Earth. Upon reaching the core-mantle boundary, fluid plumes can lead to the expulsion of magnetic field lines into the mantle. This phenomenon is known as polar magnetic upwelling. Recent models suggest that polar magnetic upwelling can occur in a manner of decades under the right conditions.
The link between core plumes and NMP changes arose out of the observation of secular changes in the core’s outer surface in a relatively small area deep beneath the New Siberian Islands.  Analysis of the mathematical function that relates core-mantle-boundary to the NMP reveals that the NMP was at just the right place to bear the full force of a large secular variation change in the 1990s.
Scientists who study Earth’s deep interior consider these magnetic field expulsions to be Earth’s analogs of sunspots, the surficial variations in solar activity that are thought to have a substantial impact on terrestrial climate. While the rapid shifting of the magnetic field is not anticipated to have any climate-related effects, it is already having profound impacts on human activities involving navigation, and will hopefully continue to shed light on the mysterious workings of Earth’s core.


One thought on “Polar Plumes cause magnetic North to drift”

  1. Howdy! I could have sworn I’ve been to this blog before but after browsing through some of the post I realized it’s new to me.
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