Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Changes in Earth’s tilt control when glacial cycles end

30.03.2005


Tilt is a 100,000-year planetary pacemaker

Scientists have long debated what causes glacial/interglacial cycles, which have occurred most recently at intervals of about 100,000 years. A new study reported in the March 24 issue of Nature finds that these glacial cycles are paced by variations in the tilt of Earth’s axis, and that glaciations end when Earth’s tilt is large.

With more than 30 explanations proposed for these glacial cycles, researchers at the Woods Hole Oceanographic Institution (WHOI) and the Massachusetts Institute of Technology (MIT) looked at the various possibilities to determine a more precise explanation. Some hypotheses suggested changes in Earth’s orbit, others that glacial cycles are caused by random climate variability. The researchers found that the most plausible cause was that variations in the tilt of the Earth’s axis control the timing of glaciations, acting as a planetary pacemaker of sorts.



Peter Huybers, a postdoctoral fellow in the WHOI Geology and Geophysics Department, and coauthor Carl Wunsch of MIT developed a simple model to look at the effects of changes in Earth’s tilt, which determines climate belts around the planet and the seasons of the year. They also focused on rapid deglaciation events known as terminations, easily identified in climate records by their magnitude and abruptness. They first estimated the timing of glacial cycles using the rate at which sediment accumulates on the ocean floor as an indicator of time. The age estimates were then used to compare the timing of the glacial cycles with the timing of changes in Earth’s orbit, known from the laws of motion and observations of the galaxy.

"Many studies have suggested a link between orbital variations and the approximately 100,000-year glacial cycles which occurred during the late Pleistocene, about 1 million to 10,000 years ago, but this is the first rigorous test of whether the glacial cycles are, in fact, paced by orbital variations," Huybers said. "We found that glaciations end near times when the Earth’s tilt, or obliquity, is large. This narrows the number of possible explanations for the glacial cycles to those which can account for the tilt pacing of glacial cycles."
Obliquity, the angle between Earth’s equatorial and orbital planes or the tilt in Earth’s axis, varies between 22.5 and 24 degrees during a cycle of 41,000 years. As the tilt increases, so does the annual average sunlight reaching high latitudes, and these are the conditions under which Huybers and Wunsch find that glaciations end. Earth’s tilt is currently 23.5 degrees and decreasing. Without the much more rapid anthropogenic or human influences on climate, Earth would probably be slowly moving toward glaciation.

"While we are confident that Earth’s tilt paces the 100,000-year glacial cycles, we were not able to determine whether another orbital effect, the precession of Earth’s equinoxes, also contributes to the pacing," Huybers said. Precession measures the slow change in the orientation of Earth’s rotation axis, similar to a spinning top, and has been the favorite explanation amongst most scientists for the timing of the glacial cycles.

One major question is how can a 40,000-year tilt cycle produce 100,000-year glacial cycles? Huybers and Wunsch suggest that during the late Pleistocene glaciation did not end every time the tilt was large, but rather that glaciers grew over two (80,000 years) or three (120,000 years) obliquity cycles before ending. The average glacial duration then gives the 100,000-year time scale.

A possible explanation for why deglaciations do not occur every 40,000 years is that ice sheets must become large enough before they are sensitive to changes in Earth’s tilt. Huybers and Wunsch developed a simple mathematical model to express this idea of changing sensitivity and showed that it gives the right timing for the glacial cycles.

Obliquity control of the recent glacial cycles provides a fresh view on the dramatic climate swings the Earth has been subjected to over the past one million years. "While the problem is far from solved, we are now one step closer to understanding the origins of the ice ages," Huybers said.

Shelley Dawicki | EurekAlert!
Further information:
http://www.whoi.edu

More articles from Earth Sciences:

nachricht International team reports ocean acidification spreading rapidly in Arctic Ocean
28.02.2017 | University of Delaware

nachricht Secrets of the calcerous ooze revealed
28.02.2017 | Washington University in St. Louis

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Scientists reach back in time to discover some of the most power-packed galaxies

28.02.2017 | Physics and Astronomy

Nano 'sandwich' offers unique properties

28.02.2017 | Materials Sciences

Light beam replaces blood test during heart surgery

28.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>