Earth Science Changes in Earth's tilt control when glacial cycles end

Discussion in 'Earth Science' started by mscbkc070904, Apr 1, 2005.

  1. mscbkc070904

    mscbkc070904 Premium Member

    Changes in Earth\'s tilt control when glacial cycles end

    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.

    Source: WHOI
  2. bodebliss

    bodebliss The Zoc-La of Kromm-B Premium Member

    It's alot more complex than they make it out.

    I read this 15 year a-gone andf there are also 150 million year cycle between Ice Epochs which are not explained by the cycles that you have stated so far.

    These might be explained by cycles within the Sun or travel around the galactic core or shifts between up galactic plane and down.

    There is also a theory that life on Earth had used up too much CO2 and stored it in the ground. That's why we're here to re-release it again.

    Also the theory of ocean circulation due to continental drift and air circulation due to mountain formation cycles and the using up of CO2 due to the breaking down of rock. which uses alot of carbonic acid.

    We are still in a Ice Epoch and as far as any scientist today knows there will be another Ice Age.

    Food for thought!

    Ps:don't forget Sun cycles cause forever scientists were taught the Sun is constant it is only recent that they have looked for Sun cycles.

    oh sweet mystery of light at last I found you!
  3. mscbkc070904

    mscbkc070904 Premium Member

    Where are you getting this from? Sources please?

    Used to much CO2 and stored it in the ground? By what means and where did you get this from? Please support your statement.

    Also, the reason we are here is to re-release it again? HUH? Clarify that statement, cause it sounds to me you are saying, the purpose of humanity is to re-release CO2???

    Say what? Where do you get these theories from?
  4. Young William

    Young William Premium Member

    Or to redundantly create????//
  5. bodebliss

    bodebliss The Zoc-La of Kromm-B Premium Member

    you didn't attribute the cycle theory to Milutin Milankovitch

    continental drft and ice epochs
    Department of Geography Home

    various theories

    Theories of the Ice Age

    animals used up CO2

    solar cause
    The Resurgent Sun - NASA Science
    Center for Global Food Issues - Growing More Per Acre Leaves More Land for Nature
    Record ice core gives fair forecast

    ice ages and galactic rotation

    here's some

    I actually enjoy backing up what I say with links , but no one else on this site seems to be doing that. My guess is everyone else is an expert with credentials,huh?