Earth's core affects length of day

July 11th, 2013
Research at the University of Liverpool has found that variations in the length of day over periods of between one and 10 years are caused by processes in the Earth's core.

The Earth rotates once per day, but the length of this day varies.  A year, 300 million years ago, lasted about 450 days and a day would last about 21 hours.

Length of day increases

As a result of the slowing down of the Earth's rotation the length of day has increased.

The rotation of the 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.

Professor Richard Holme, from the School of Environmental Sciences, studied the variations and fluctuations in the length of day over a one to 10 year period between 1962 and 2012.  The study took account of the effects on the Earth's rotation of atmospheric and oceanic processes to produce a model of the variations in the length of day on time scales longer than a year.

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.

More information:
phys.org/news/2013-07-pair-yea… ions-length-day.html

Provided by University of Liverpool

This Phys.org Science News Wire page contains a press release issued by an organization mentioned above and is provided to you “as is” with little or no review from Phys.Org staff.

More news stories

Teen sleeplessness piles on risk for obesity

Teenagers who don't get enough sleep may wake up to worse consequences than nodding off during chemistry class. According to new research, risk of being obese by age 21 was 20 percent higher among 16-year-olds who got less ...

Celebrating 100 years of crystallography

To commemorate the 100th anniversary of a revolutionary technique that underpins much of modern science, Chemical & Engineering News (C&EN) magazine last week released a special edition on X-ray crystallography—its past, ...

NASA image: Signs of deforestation in Brazil

Multiple fires are visible in in this image of the Para and Mato Grosso states of Brazil. Many of these were most likely intentionally set in order to deforest the land. Deforestation is the removal of a ...

NASA sees Tropical Storm Lowell's tough south side

The south side of Tropical Storm Lowell appears to be its toughest side. That is, the side with the strongest thunderstorms, according to satellite imagery from NOAA's GOES-14 and NASA-NOAA's Suomi NPP satellites.