Changes in CO2 levels caused Greenland to be covered in ice
Washington, August 28 : The transition from the mostly ice-free Greenland of three
million years ago, to the ice-covered region that we see today, can be attributed to
changes in the carbon dioxide (CO2) levels.
Though there have been many reports in the media about the effects of global warming on
the Greenland ice-sheet, there is still great uncertainty as to why there is an ice-sheet
there at all.
Now, scientists at the University of Bristol and the University of Leeds in the UK,
show that only changes in atmospheric carbon dioxide are able to explain the transition
from the mostly ice-free Greenland of three million years ago, to the ice-covered
Greenland of today.
Understanding why the ice formed on Greenland three million years ago will help
understand the possible response of the ice sheet to future climate change.
According to Dr Dan Lunt from the University of Bristol and funded by the British
Antarctic Survey, "Evidence shows that around three million years ago, there was an
increase in the amount of rock and debris deposited on the ocean floor around
Greenland."
"These rocks could not have got there until icebergs started to form and could
transport them, indicating that large amounts of ice on Greenland only began to form about
three million years ago," he added.
"Prior to that, Greenland was largely ice-free and probably covered in grass and
forest. Furthermore, atmospheric carbon dioxide levels were relatively high. So, the
question we wanted to answer was why did Greenland become covered in an ice-sheet?" said
Dr Lunt.
There are several competing theories, ranging from changes in ocean circulation, the
increasing height of the Rocky Mountains, changes in the Earth's orbit, and natural
changes in atmospheric greenhouse gas concentrations.
Using state-of-the-art computer climate and ice-sheet models, Lunt and colleagues
decided to test which, if any, of these theories was the most credible.
While the results suggest that climatic shifts associated with changes in ocean
circulation and tectonic uplift did affect the amount of ice cover, and that the ice waxed
and waned with changes in the Earth's orbit, none of these changes were large enough to
contribute significantly to the long-term growth of the Greenland ice sheet.
Instead, the new research suggests that the dominant cause of the Greenland glaciation
was the fall from high atmospheric carbon dioxide levels to levels closer to that of
pre-industrial times.
Today, concentrations are approaching the levels that existed while Greenland was
mostly ice-free.
--ANI
