Study heats up 'snowball Earth' debate (Forwarded)
Andrew Yee
University of Toronto
Toronto, Canada
Contact:
Department of Public Affairs
Tel: (416) 978-8638
March 25, 2008
Study heats up 'snowball Earth' debate
By Maria Saros Leung
Research by University Professor Richard Peltier of physics reveals that the
Earth's surface 700 million years ago may have been warmer than previously
thought.
Peltier developed a climate model that casts doubt on the popular 'snowball
Earth' hypothesis, a theory that posits the Earth was completely covered in
ice and photosynthesis ceased during the late Neoproterozoic period.
The U of T physicist has found that the Neoproterozoic ocean's natural
carbon cycle produced a 'negative feedback reaction' that actually prevented
the equator region from completely freezing over, allowing photosynthesis to
occur.
Peltier's recent findings have found resonance among evolutionary
biologists. The late Neoproterozoic period gave rise to arguably the most
important period in Earth's biological history -- the Cambrian period. It
was during this time when the major groups of animal life exploded onto the
fossil record. Rock samples containing evidence of early organic life --
ancestors to photosynthetic life -- have been dated to before and after
glacial periods. The idea that these ancestors to photosynthetic life could
have existed during a period when there was no photosynthesis has been a
topic of much debate.
"As the temperature of the Neoproterozoic ocean cools and moves towards a
snowball state, more organic carbon is converted into carbon dioxide. The
oxygen is drawn down out of the atmosphere into the ocean, re-mineralizing
the organic matter and forcing respiration," Peltier explained. "When
respiration occurs, it generates carbon dioxide, part of which remains
dissolved in the ocean, but part of which is forced out of the ocean into
the atmosphere which enhances the greenhouse effect and prevents the
cooling."
"The mathematical model supports oscillatory glaciations and de-glaciations
on a timescale that's similar to the timescale that people have argued were
appropriate for the Neoproterozoic," he added.
Doctoral student Yonggang Liu and John Crowley, a former summer research
student in Peltier's lab, now pursuing doctoral studies at Harvard,
co-authored the paper, published in Nature late last year.
The study builds on the findings published by Professor Dan Rothman from the
Massachusetts Institute of Technology that suggest that the Neoproterozoic
ocean was very rich in carbon life and findings published by Peltier on the
cover of Nature in 2000 that, for the first time, demonstrated that while
huge deep glaciations did exist, a large amount of water near the equator
was left unfrozen. At the time, adherents to the 'snowball Earth' theory
coined the term 'slushball Earth' to describe Peltier's findings.