Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Earth Science News .




ICE WORLD
Penn Study Finds Earlier Peak for Spain's Glaciers
by Staff Writers
Philadelphia PA (SPX) Sep 10, 2013


A ring of boulders marks the former margin of an ancient glacier.

The last glacial maximum was a time when Earth's far northern and far southern latitudes were largely covered in ice sheets and sea levels were low. Over much of the planet, glaciers were at their greatest extent roughly 20,000 years ago. But according to a study headed by University of Pennsylvania geologist Jane Willenbring, that wasn't true in at least one part of southern Europe.

Due to local effects of temperature and precipitation, the local glacial maximum occurred considerably earlier, around 26,000 years ago. The finding sheds new light on how regional climate has varied over time, providing information that could lead to more-accurate global climate models, which predict what changes Earth will experience in the future.

Willenbring, an assistant professor in Penn's Department of Earth and Environmental Science in the School of Arts and Sciences, teamed with researchers from Spain, the United Kingdom, China and the United States to pursue this study of the ancient glaciers of southern Europe.

"We wanted to unravel why and when glaciers grow and shrink," Willenbring said.

In the study site in central Spain, it is relatively straightforward to discern the size of ancient glaciers, because the ice carried and dropped boulders at the margin. Thus a ring of boulders marks the edge of the old glacier.

It is not as easy to determine what caused the glacier to grow, however. Glaciers need both moisture and cold temperatures to expand. Studying the boulders that rim the ancient glaciers alone cannot distinguish these contributions. Caves, however, provide a way to differentiate the two factors.

Stalagmites and stalactites - the stony projections that grow from the cave floor and ceiling, respectively - carry a record of precipitation because they grow as a result of dripping water.

"If you add the cave data to the data from the glaciers, it gives you a neat way of figuring out whether it was cold temperatures or higher precipitation that drove the glacier growth at the time," Willenbring said.

The researchers conducted the study in three of Spain's mountain ranges: the Bejar, Gredos and Guadarrama. The nearby Eagle Cave allowed them to obtain indirect precipitation data.

To ascertain the age of the boulders strewn by the glaciers and thus come up with a date when glaciers were at their greatest extent, Willenbring and colleagues used a technique known as cosmogenic nuclide exposure dating, which measures the chemical residue of supernova explosions.

They also used standard radiometric techniques to date stalagmites from Eagle Cave, which gave them information about fluxes in precipitation during the time the glaciers covered the land.

"Previously, people believe the last glacial maximum was somewhere in the range of 19-23,000 years ago," Willenbring said. "Our chronology indicates that's more in the range of 25-29,000 years ago in Spain."

The geologists found that, although temperatures were cool in the range of 19,000-23,000 years ago, conditions were also relatively dry, so the glaciers did not regain the size they had obtained several thousand years earlier, when rain and snowfall totals were higher. They reported their findings in the journal Scientific Reports.

Given the revised timeline in this region, Willenbring and colleagues determined that the increased precipitation resulted from changes in the intensity of the sun's radiation on the Earth, which is based on the planet's tilt in orbit. Such changes can impact patterns of wind, temperature and storms.

"That probably means there was a southward shift of the North Atlantic Polar Front, which caused storm tracks to move south, too," Willenbring said. "Also, at this time there was a nice warm source of precipitation, unlike before and after when the ocean was colder."

Willenbring noted that the new date for the glacier maximum in the Mediterranean region, which is several thousands of years earlier than the date the maximum was reached in central Europe, will help provide more context for creating accurate global climate models.

"It's important for global climate models to be able to test under what conditions precipitation changes and when sources for that precipitation change," she said. "That's particularly true in some of these arid regions, like the American Southwest and the Mediterranean."

When glaciers were peaking in the Mediterranean around 26,000 years ago, the American Southwest was experiencing similar conditions. Areas that are now desert were moist. Large lakes abounded, including Lake Bonneville, which covered much of modern-day Utah. The state's Great Salt Lake is what remains.

"Lakes in this area were really high for 5,000-10,000 years, and the cause for that has always been a mystery," Willenbring said. "By looking at what was happening in the Mediterranean, we might eventually be able to say something about the conditions that led to these lakes in the Southwest, too."

This research was supported by the Ministerio de Ciencia e Innovacion and the Junta de Comunidades de Castilla-La Mancha.

.


Related Links
University of Pennsylvania
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
Melting water's lubricating effect on glaciers has only 'minor' role in future sea-level rise
Bristol, UK (SPX) Aug 14, 2013
Scientists had feared that melt-water which trickles down through the ice could dramatically speed up the movement of glaciers as it acts as a lubricant between the ice and the ground it moves over. But in a paper published in PNAS, a team led by scientists from the University of Bristol found it is likely to have a minor role in sea-level rise compared with other effects like iceberg prod ... read more


ICE WORLD
Australia reiterates tough asylum boat policy

Niger asks for foreign help for flood victims

Olympics: Tokyo 2020 is a bid in the shadow of Fukushima

Italy says Syria crisis to worsen refugee problem

ICE WORLD
New computational approaches speed up the exploration of the universe

Advancing graphene for post-silicon computer logic

Simple compact laser system could detect presence of explosives

Northrop Grumman Completes Demonstration of 3D Expeditionary Long-Range Radar (3DELRR) System

ICE WORLD
Using a form of 'ice that burns' to make potable water from oil and gas production

'La Nada' Pacific ocean patterns make forecasting difficult

Can we save our urban water systems?

Why does the area over southern high and sub tropical latitudes have more frequent and stronger rains?

ICE WORLD
Penn Study Finds Earlier Peak for Spain's Glaciers

East Antarctic Ice Sheet could be more vulnerable to climate change than previously thought

On warming Antarctic Peninsula, moss and microbes reveal unprecedented ecological change

Arctic Sea Ice Update: Unlikely To Break Records, But Continuing Downward Trend

ICE WORLD
A genetic treasure hunting in sorghum may benefit crop improvement

Report proposes microbiology's grand challenge to help feed the world

Spread of crop pests threatens global food security as Earth warms

Study forecasts future water levels of crucial agricultural aquifer

ICE WORLD
Tropical storm Gabrielle heads for Bermuda: forecasters

Japan scraps stranded tsunami ship

Lorena weakens into tropical depression off Mexico

Power outages, landslides after strong Guatemala quake

ICE WORLD
Guinea-Bissau rules out amnesty for coup leaders

Sudan bombs S. Sudan buffer zone position, kills 2: Juba

Origin of state of ancient Egypt given new time line

Defence chiefs meet over DR Congo conflict

ICE WORLD
New data reveals that the average height of European males has grown by 11cm in just over a century

Hidden shell middens reveal ancient human presence in Bolivian Amazon

Look at what I'm saying

The true raw material footprint of nations




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