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| Researchers studied the variations and fluctuations in the length of day over a one to 10 year period between 1962 and 2012 [Credit: University of Liverpool] |
Length of day increases
As a result of the slowing down of Earth's rotation the length of day has increased. The rotation of Earth on its axis, however, is affected by a number of other factors -- for example, the force of the wind against mountain ranges changes the length of the day by plus or minus a millisecond over a period of a year.
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| The form of core motions giving rise to variations in Earth’s length of day [Credit: University of Liverpool] |
Professor Holme said: "The model shows well-known variations on decadal time scales, but importantly resolves changes over periods between one and 10 years.
"Previously these changes were poorly characterised; the study shows they can be explained by just two key signals, a steady 5.9 year oscillation and episodic jumps which occur at the same time as abrupt changes in the Earth's magnetic field, generated in the Earth's core.
He added: "This study changes fundamentally our understanding of short-period dynamics of the Earth's fluid core. It leads us to conclude that the Earth's lower mantle, which sits above the Earth's outer core, is a poor conductor of electricity giving us new insight into the chemistry and mineralogy of the Earth's deep interior."
The research was conducted in partnership with the Université Paris Diderot and is published in Nature.
Source: University of Liverpool [July 11, 2013]