Subscribe to our free daily newsletters
. 24/7 Space News .




Subscribe to our free daily newsletters



Changes In Earth's Tilt Control When Glacial Cycles End

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.
Woods Hole MA (SPX) Mar 30, 2005
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.

Related Links
Woods Hole Oceanographic Institution
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express

Ice Core Indicates West Antarctic Ice Has Thinned Less Than Believed
Seattle WA (SPX) Mar 24, 2005
Rising sea levels 20,000 years ago, as the last ice age was beginning to wane, often are attributed in part to melting in West Antarctica.



Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only






Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News








The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.