ANTARCTIC ICE SHEET HARDLY AS STABLE AS HAS BEEN THOUGHT
COLUMBUS, Ohio -- The clues to the history of a massive ice sheet that covers most of Eastern Antarctica may have been found more than 1,800 miles away on the North Island of New Zealand.
There, scientists have found perhaps the best record so far of ancient sea levels that can be traced to historic changes in the Antarctic ice sheet.
The new findings suggest that what seems to be one of the most stable features on the globe -- the Antarctic ice sheet -- may in fact be changing rapidly on a geologic time frame. And those changes had a dramatic impact on the shorelines of the world's continents.
The discovery may provide important information about the possible impact future climate changes could have on the planet. These findings were reported October 24 in Seattle at the annual meeting of the Geological Society of America.
Scientists have argued for more than a decade over how stable the East Antarctic ice sheet actually is. This mile-thick covering of ice, if melted, contains enough water to cause global sea levels to rise nearly 200 feet -- the height of a 12-story
Some research has suggested the ice sheet greatly diminished in size sometime in the last several million years while other studies supported the idea that the ice was extremely stable. Discovering which theory is more accurate would provide clues to the impact global warming might have on rising world sea levels.
Gary Wilson, a post-doctoral fellow at the Byrd Polar Research Center at Ohio State University, believes he's found part of the answer in a three-mile-thick section of rock that was once ancient shorelines on New Zealand.
In that rock which was once sand, mud, and beds of discarded shells, he found a record of changing global sea levels dating back through the later part of the Neogene period, between two million and six million years ago.
That record clearly showed that at its highest point, between three and five million years ago, sea level was about 140 feet higher than it is today, Wilson said. And between two million and three million years ago, global sea level dropped progressively until it was easily 65 feet lower than it is today.
"The most striking thing about this record is the variability it shows," Wilson explained. "There are more than 30 rises and falls of global sea level -- changes of as much as 65 feet -- between two and six million years ago."
Wilson is convinced that those sea level changes are directly linked to a decaying and replenishment of the ice covering Antarctica. If true, that means that the ice sheet has been much smaller than it is today -- perhaps less than half its present size -- during that period of between three million and five million years ago.
The record also shows that small scale changes in the ice sheet -- reductions and increases of at least a quarter of the current ice sheet -- could be occurring as often as every 300,000 years. Larger changes -- reductions and increases of perhaps more than half of the current ice sheet -- could take place every 3 million years.
Wilson began his work while he was a doctoral student at Victoria University of Wellington, New Zealand.
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Contact: Gary Wilson, (614) 292-6531
Written by Earle Holland, (614) 292-8384