New Evidence of Early Glacial Development, History of Antarctic Ice Sheet Revised

May 05, 2006
New Evidence of Early Glacial Development, History of Antarctic Ice Sheet Revised
Sediments characteristic of deposition by glacial ice near the Eocene-Oligocene boundary on Seymour Island. Credit: Linda C. Ivany

Syracuse University Professors Linda C. Ivany and Scott D. Samson along with colleagues at the University of Leuven in Belgium and Hamilton College have found evidence that expands our understanding about how the ice sheet covering most of Antarctica really began. Their findings were published in the article “Evidence for an Earliest Oligocene Ice Sheet on the Antarctic Penninsula,” in the May 2006 issue of the journal, Geology. The research was supported by funding from the National Science Foundation’s Office of Polar Programs.

“One of the most fundamental climate shifts that this planet has undergone since the events that precipitated the extinction of the dinosaurs is the so-called
‘greenhouse to icehouse transition’—the time when Earth went from having virtually no ice on it at all to one with a more or less permanent ice sheet covering Antarctica,” says Ivany, professor of earth science in The College of Arts and Sciences at SU and principal investigator on the project. “This happened about 34 million years ago, and is marked by dramatic changes in the chemistry of the oceans and the appearance of ‘ice rafted debris’ in ocean sediments around Antarctica, carried there by icebergs from land that floated out and melted far from the continent, releasing the sand and rock that had been frozen into them.”

Though scientists are quite sure that glaciers grew on Antarctica at this time, it is not clear where that ice was, nor how much of it there was initially. This is because most of the continent is now under the ice, and it is difficult to find places where sediments are exposed that record this interval of time.

Until now, the assumption has been that glaciers were confined to the eastern part of Antarctica, where the biggest ice sheet is today. Ivany’s research team found evidence that glaciers may have covered a much bigger area at the early stages of this transition. Sediments on Seymour Island, off the northern tip of the Antarctic Peninsula, have been dated to just this time, and show features characteristic of deposition by glacial ice. Because this island is at the far northern reaches of the Peninsula, in western Antarctica, they suggest that the initial pulse of glaciation was far more extensive than originally suspected.

Scientists believe that growth of the Antarctic ice sheet was initiated by a drop in greenhouse gas concentrations in the atmosphere in combination with a change in ocean circulation caused by South America pulling away from Antarctica. The climatic response to these gradual changes now appears to be even bigger than previously thought, showing that Earth cooled fast enough to allow the growth of ice on the entire continent all at once.

Ivany’s team concludes that because Earth’s climate system is capable of shifting this rapidly and dramatically to such a new and different state, their discovery may provide an insight into how things could change in the future if we continue to alter our environment.

Source: Syracuse University

Explore further: Cordilleran terrane collage

add to favorites email to friend print save as pdf

Related Stories

Clock Is ticking in West Antarctic

May 26, 2014

Reports that a portion of the West Antarctic Ice Sheet has begun to irretrievably collapse, threatening a 4-foot rise in sea levels over the next couple of centuries, surged through the news media last week. ...

Antarctica's ice losses on the rise

May 19, 2014

Three years of observations show that the Antarctic ice sheet is now losing 159 billion tonnes of ice each year – twice as much as when it was last surveyed.

Time-lapse of the 'unstable' West Antarctic ice shee

May 13, 2014

The new finding that the eventual loss of a major section of West Antarctica's ice sheet "appears unstoppable" was not completely unexpected by scientists who study this area. The study, led by glaciologist ...

Recommended for you

Cordilleran terrane collage

9 hours ago

In the August 2014 issue of Lithosphere, Steve Israel of the Yukon Geological Survey and colleagues provide conclusions regarding the North American Cordillera that they say "are provocative in that they b ...

NASA sees Tropical Storm Halong's 'best side'

12 hours ago

NASA satellite data showed Tropical Storm Halong's "best side" or most powerful side was east of its center. That's where the coldest cloud top temperatures and strongest thunderstorms appeared on satellite ...

User comments : 0