Skip to: Content Skip to: Site Navigation Skip to: Search
Scientists have long tried to figure out what causes the ebb and
flow of ice ages. New data suggests a novel explanation for why
the mile-thick blankets of ice retreat so quickly: They become
too heavy.  (Page 2 of 2)  The team also weighed the relative
contributions of changes in atmospheric concentrations of carbon
dioxide, a greenhouse gas, to the 100,000-year glacial cycles.
Skip to next paragraph  While carbon dioxide decreased as the
ice sheet expanded and cooled the climate and increased again as
the climate warmed, CO2 levels did not determine the overall
sequence of events during each 100,000-year cycle, the
researchers concluded.  The simulations also showed how the
interplay between orbital and climate influences kept North
America's ice sheets growing, even as a significant but smaller
ice sheet building in northern Eurasia waxed and waned based on
orbital changes happening at 40,000- and 20,000-year intervals.
Looking closely at the la