Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ice core ’dipstick’ indicates West Antarctic ice has thinned less than believed

23.03.2005


Rising sea levels 20,000 years ago, as the last ice age was beginning to wane, often are attributed in part to melting in West Antarctica.

But in a new study led by University of Washington researchers, an ice core of 1,000 meters was used as a sort of dipstick to show that a key section of the West Antarctic Ice Sheet probably never contained as much ice as scientists originally thought it did. That means it couldn’t have contributed as much to the higher sea level. In an area called Siple Dome, the ice sheet currently rises 1,000 meters – more than half a mile – above a bedrock plateau. Some computer reconstructions indicate it was perhaps twice as thick at the end of the last ice age, also called the Last Glacial Maximum.

But evidence from an ice core extracted near Siple Dome from 1997-99, along with other calculations, indicates ice in that area has lost only 200 to 400 meters of its thickness in the last 20,000 years, said Edwin Waddington, a UW professor of Earth and space sciences. Like water on a hillside, Siple Dome ice flows down into adjacent ice streams, where it continues to the nearby Ross Ice Shelf, a part of a bay on the Ross Sea that is covered with floating glacier ice. "Then the whole thing spreads out like oil on water," Waddington said.



The West Antarctic Ice Sheet once rested on the bottom of the bay all the way to its "grounding line" at the continental margin in the Ross Sea. However, that ice has retreated substantially in the last 20 millennia, at the same time Siple Dome was thinning. Part of the puzzle has been whether the ice streams were flowing, whether they carried interior ice to the ice shelf at the end of the last ice age, and whether they began where they do now or receded along with the ice shelf’s grounding line.

Studying the ice core layer by layer, each representing one year’s worth of snowfall compacted into a very thin band, researchers were able to extract an isotope record that provided a picture of temperature and snowfall patterns near Siple Dome. The layers get thinner and thinner with depth, as more ice and snow piles up. But the thinness of the layers deposited near the end of the Last Glacial Maximum indicate the ice also was being thinned by ice streams that were flowing even then, probably starting in about the same places they do now. "If you are making the ice sheet thinner over time, you’re also stretching it much farther, so the individual layers get much thinner than they would be in a steady state," Waddington said.

Waddington is lead author of a paper describing the research, which is being published online March 23 in Geology, a journal of the Geological Society of America. Co-authors are Howard Conway and Eric Steig of the UW; Richard Alley of Pennsylvania State University; Edward Brook of Oregon State University; Kendrick Taylor of the Desert Research Institute at the University of Nevada, Reno; and James White of the University of Colorado.

Previous data have shown that, in the ice age, glacial ice built to quite high elevations in the mountains just inland from the Ross Ice Shelf. That led to the expectation that Siple Dome had to be substantially thicker than it is now as the ice moved from the mountains to the ice shelf. But the new study shows the ice could not be thick at Siple dome, so ice must have flowed toward the ocean with a very gentle slope for more than 600 miles. An ice sheet with such a low profile and gradual decline would have had to have a very slippery bed to maintain its continuous flow, Waddington said, and it appears the ice flowed vigorously despite being relatively thin.

One major implication of the research, he said, is that it disputes the theory that West Antarctic ice streams retreated when the ice shelf did. In the last ice age, the ice streams near Siple Dome had to be roughly where they are now to keep the dome from building up more ice.

By giving a clearer picture of the site where snow was deposited and eventually turned to glacial ice, the work gives scientists new information for interpreting climate in the last ice age and since, which is key to understanding how climate is changing today, Waddington said. "To make climate judgments based on the past requires knowing the past climate accurately," he said.

Vince Stricherz | EurekAlert!
Further information:
http://www.washington.edu

More articles from Earth Sciences:

nachricht NASA examines Peru's deadly rainfall
24.03.2017 | NASA/Goddard Space Flight Center

nachricht Steep rise of the Bernese Alps
24.03.2017 | Universität Bern

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>