Researchers Develop New Model of Ice Volume Change Based on Earth's Orbital Patterns 23 June 2006

Through dated geological records scientists have Raymo and Lisiecki are proposing that during this known for decades that variations in the Earth’s time, ice volume changes occurred in both the orbit around the sun – subtle changes in the Northern Hemisphere and Antarctica, each distance between the two – control ice ages. But, controlled by different amounts of local summer for the first 2 million years of the Northern insolation paced by precession. Hemisphere Ice Age there has always been a mismatch between the timing of ice sheet changes “The reason the frequency is not observable in and the Earth’s orbital parameters. records is because ice volume change occurred at both poles, but out of phase with each other. When A new model of ice volume change developed by ice was growing in the Northern Hemisphere, it was Maureen Raymo and Lorraine Lisiecki, researchers melting in the Southern,” said Raymo. in Boston University's Department of Earth Sciences, proposes a reason for this discrepancy. The team believes scientists have been operating Like other models, it is consistent with traditional under the assumption that Antarctica has been Milankovitch theory – which holds that the three exceptionally stable for 3 million years and very cyclical changes in the Earth’s orbit around the difficult to change climatically. Sun (obliquity, precession, and eccentricity) influence the severity of seasons and high latitude “We don’t tend to think of ice volume in that region temperatures over time. However, the new model as varying significantly, even on geologic time differs from earlier ones in that it allows for a much scales,” said Raymo. “However, only a modest more dynamic Antarctic ice sheet. change in Antarctic ice mass is required to “cancel” a much larger Northern ice volume According to the researchers, from 3 million years signal.” ago to about 0.8 million years ago, Northern Hemisphere ice volume appears to have varied Records used to measure the ice volume, such as mostly with the 41,000 year period of obliquity – sea levels, integrate the whole world. According to the periodic shift in the direction or tilt of Earth’s Raymo, the new model demonstrates that while the axis. However, summer insolation (incoming solar precession frequency is actually strong in ice radiation), which is widely believed to be the major volume changes at each pole, in geologic records, influence on high-latitude climate and ice volume Northern and Southern hemisphere ice volume change, is typically dominated by the 23,000 year trends act to cancel each other out at this precessional period – the slow “wobble” of the frequency. Earth on its axis. The paper, which was published online today and “Because summer insolation is controlled by will appear in an upcoming issue of the journal precession, and summer heating controls ice sheet Science, proposes that the Antarctic ice sheet is mass balance, it is difficult to understand why the more dynamic and far more capable of change than ice volume record is dominated by the obliquity previously believed. frequency,” said Dr. Raymo. “It’s not a complete mismatch, but the precession frequency we think “If our theory holds true, it is a cause for concern should be strong in geological records is not.” with regard to climate changes not associated with

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orbital patterns as well,” said Raymo.

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Source: Boston University

APA citation: Researchers Develop New Model of Ice Volume Change Based on Earth's Orbital Patterns (2006, June 23) retrieved 24 September 2021 from https://phys.org/news/2006-06-ice-volume-based- earth-orbital.html

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