Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. 24/7 Space News .




ICE WORLD
Sea level rise less from Greenland, more from Antarctica
by Staff Writers
Madison WI (SPX) Aug 04, 2011


illustration only

During the last prolonged warm spell on Earth, the oceans were at least four meters - and possibly as much as 6.5 meters, or about 20 feet - higher than they are now.

Where did all that extra water come from? Mainly from melting ice sheets on Greenland and Antarctica, and many scientists, including University of Wisconsin-Madison geoscience assistant professor Anders Carlson, have expected that Greenland was the main culprit.

But Carlson's new results, published July 29 in Science, are challenging that assertion, revealing surprising patterns of melting during the last interglacial period that suggest that Greenland's ice may be more stable - and Antarctica's less stable - than many thought.

"The Greenland Ice Sheet is melting faster and faster," says Carlson, who is also a member of the Center for Climatic Research in the Nelson Institute for Environmental Studies. But despite clear observations of that fact, estimates of just how much the ice will melt and contribute to sea level rise by the end of this century are highly varied, ranging from a few centimeters to meters.

"There's a clear need to understand how it has behaved in the past, and how it has responded to warmer-than-present summers in the past."

The ice-estimation business is rife with unknown variables and has few known physical constraints, Carlson explains, making ice sheet behavior - where they melt, how much, how quickly - the largest source of uncertainty in predicting sea level rises due to climate change.

His research team sought a way to constrain where ice remained on Greenland during the last interglacial period, around 125,000 years ago, to better define past ice sheet behavior and improve future projections.

The researchers analyzed silt from an ocean-floor core taken from a region off the southern tip of Greenland that receives sediments carried by meltwater streams off the ice sheet.

They used different patterns of radiogenic isotopes to identify sources of the sediment, tracing the silt back to one of three "terranes" or regions, each with a distinct geochemical signature. The patterns of sedimentation show which terranes were still glaciated at that time.

"If the land deglaciates, you lose that sediment," Carlson explains. But to their surprise, they found that all the terranes were still supplying sediment throughout the last interglacial period and thus still had some ice cover.

"The ice definitely retreated to smaller than present extent and definitely raised sea level to higher than present" and continued to melt throughout the warm period, he adds, but the sediment analysis indicates that "the ice sheet seems to be more stable than some of the greater retreat values that people have presented."

The team used their results to evaluate several existing models of Greenland ice sheet melting during the last interglacial period. The models consistent with the new findings indicate that melting Greenland ice was responsible for a sea level rise of 1.6 to 2.2 meters - at most, roughly half of the minimum four-meter total increase.

Even after accounting for other Arctic ice and the thermal expansion of warmer water, most of the difference must have come from a melting Antarctic ice sheet, Carlson says.

"The implication of our results is that West Antarctica likely was much smaller than it is today," and responsible for much more of the sea level rise than many scientists have thought, he says. "If West Antarctica collapsed, that means it's more unstable than we expected, which is quite scary."

Ultimately, Carlson says he hopes this line of research will improve the representation of ice sheet responses to a warming planet in future Intergovernmental Panel on Climate Change (IPCC) reports. Temperatures during the last interglacial period were similar to those expected by the end of this century, and present-day temps have already reached a point that Greenland's glaciers are melting.

The Science paper was co-authored by UW-Madison colleagues Elizabeth Colville, Brian Beard, Alberto Reyes, and David Ullman and Oregon State University researchers Robert Hatfield and Joseph Stoner, and supported by UW-Madison and the National Science Foundation.

.


Related Links
University of Wisconsin-Madison
Beyond the Ice Age






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





ICE WORLD
Russia may lose 30% of permafrost by 2050: official
Moscow (AFP) July 29, 2011
Russia's vast permafrost areas may shrink by a third by the middle of the century due to global warming, endangering infrastructure in the Arctic zone, an emergencies ministry official said Friday. "In the next 25 to 30 years, the area of permafrost in Russia may shrink by 10-18 percent," the head of the ministry's disaster monitoring department Andrei Bolov told the RIA Novosti news agency. ... read more


ICE WORLD
"Big Splat" May Explain The Moon's Mountainous Far Side

LADEE Completes Mission Critical Design Review

Moon's mountains made by slo-mo crash: study

Unique volcanic complex discovered on Lunar far side

ICE WORLD
Flowing water on Mars sparks new hunt for life traces

Opportunity Past 20-Mile Mark As it Nears Large Crater

NASA Spacecraft Data Suggest Water Flowing on Mars

NASA's Next Mars Rover to Land at Gale Crater

ICE WORLD
Welsh tech firm starting U.S. company

Invisibility cloak closer to reality

India eyes manned space missions

Satellite innovators launch smartphone Space App competition

ICE WORLD
Why Tiangong is not a Station Hub

China to launch experimental satellite in coming days

Spotlight Time for Tiangong

China launches new data relay satellite

ICE WORLD
The Orbital Perspective of Astronaut Ron Garan

Voyage to Vaccine Discovery Continues with Space Station Salmonella Study

New uses for Space Station

ISS to be sunk after 2020: Russian space agency

ICE WORLD
64 satellites launched by ISRO so far

Inmarsat Selects ILS Proton For Inmarsat-5

United Launch Alliance Saves Money with First Combined Atlas and Delta Shipments on Mariner

Russia sends observation satellite into space

ICE WORLD
Exoplanet Aurora Makes For An Out-of-this-World Sight

Distant planet aurorae modeled

Exoplanet Aurora: An Out-of-this-World Sight

Ten new distant planets detected

ICE WORLD
Editions, AOL's entrant in iPad news reader race

Penn Chemists Make First Molecular Binding Measurement of Radon

Japanese parents live with radiation fear

Radar system could makes runways safer




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement