Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sand Dunes Reveal Unexpected Dryness During Heavy Monsoon

08.10.2009
The windswept deserts of northern China might seem an odd destination for studying the heavy monsoon rains that routinely drench the more tropical regions of Southeast Asia.

But the sandy dunefields that mark the desert margin between greener pastures to the south and the Gobi Desert to the north are a rich source of information about past climates in Asia, says University of Wisconsin-Madison geographer Joseph Mason. Wetter periods allow vegetation to take root on and stabilize sand dunes. During dry spells, plants die off and the dunes are more active, constantly shifting as sand is blown away and replenished.

Such patterns of dune activity provide a history of the area’s climate — if one can read them, Mason says. “When did those periods of stability or activity occur and from that, what can we infer about climate change?”

As reported in a new paper in the October issue of the journal Geology, Mason and colleagues mapped sand dune activity across northern China and found unexpectedly high levels of mobility and change 8,000 to 11,500 years ago, a time period generally thought to have a wetter climate. The result challenges existing ideas about the monsoon’s regional influence and could impact future climate predictions.

Today, the dunes are at the edge of the monsoon region and the scientists expected to find close correlation between precipitation in the dunefields and the strength of the monsoon.

What they found instead was rather surprising. “They turn out to be almost completely out of phase,” Mason says. “Where we find lots of active dunes turns out to be a time when the monsoon system is supposed to have been stronger in southern and central China.”

Part of the explanation may lie in local patterns of atmospheric circulation. At the peak of the summer monsoon, central China experiences both heavy summer rainfall and strong upward airflow. That upward flow tends to be balanced out by more downward air motion — which suppresses precipitation — in areas north and west of the monsoon core.

Regional climate modeling data from the UW-Madison Center for Climatic Research, led by co-author and UW-Madison professor of atmospheric and oceanic sciences Zhengyu Liu, shows that this pattern may have been strengthened between 8,000 and 11,500 years ago. The models also show high summer temperatures at that time, which would have increased evaporation and further reduced the moisture that supports dune-stabilizing plants.

This pattern of climate change had been described for areas distant from the monsoon, like Central Asia around the Caspian and Aral Seas and in northern Mongolia. However, Mason says, “It hasn’t really been recognized that this effect could be going on in northern China, which is where our study sites are. What it means is there’s much more of a contrast in climate change across a fairly short distance.”

The new findings relied on a technique called optically stimulated luminescence (OSL), which dates the last time the sand was exposed to sunlight. Radiocarbon dating methods are of limited use since sand typically contains little or no organic material. The OSL method identifies time periods when the sand was actively moving around, indicating little precipitation, and times when dunes were stable.

Mason’s previous work in the area suggests that moisture and precipitation are the most significant factors in determining the activity of the Chinese dunes. The new results mean that common assumptions about the effects of future climate changes — including the increased monsoon rainfall predicted by many climatologists — may be incorrect.

“If monsoon rainfall increases in southern China over the next century, the logical assumption would be that these dunes would become more stable as more precipitation also reaches the dune fields and increases vegetation cover,” Mason says. “That may not be true… The dunes can become active and the climate there can become drier even when the monsoon is getting stronger.”

Even if future rainfall in northern China isn’t reduced by changing air circulation patterns as it was in the past, rising temperatures will undoubtedly increase evaporation, he says, exacerbating the water shortages that already plague the area. An accompanying increase in sand dune activity would reduce available grazing land and worsen air quality.

“If it’s drier you have less vegetation and the dunes are active. There will almost certainly be more dust produced, which is a major environmental hazard. Some of the dust from northern China actually reaches Korea, Japan and even the western U.S.,” says Mason.

The paper is co-authored by colleagues in China, the Illinois State Geological Survey, and the University of Nebraska-Lincoln. Funding was provided by the National Science Foundation, the National Natural Science Foundation of China, the China National S&T Basic Work Program, and Nanjing University.

CONTACT: Joseph Mason, mason@geography.wisc.edu, 608-262-6316

Jill Sakai | Newswise Science News
Further information:
http://www.wisc.edu
http://www.news.wisc.edu/newsphotos/otindagDunefield09.html

More articles from Earth Sciences:

nachricht Ice cave in Transylvania yields window into region's past
28.04.2017 | National Science Foundation

nachricht Citizen science campaign to aid disaster response
28.04.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>