Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Dwarf Dunes Record Climate History in Desert Sand

03.05.2018

Wind-driven sand is understood to create ripples on a centimetre scale and dunes spanning tens of metres, but so-called megaripples of intermediate size have remained puzzling. A theory of aeolian sand sorting now fills the gap, suggesting that megaripples and similar structures seen on Mars might hold encrypted records of the local climate history.

Sandy deserts aren't smooth. Like water surfaces, they are decorated by tiny surface ripples and much larger waves, called dunes, excited by turbulent winds. Now, writing in Nature Physics, an international team of geomorphologists and physicists elucidates the physical mechanism creating a third type of sand wave, with no marine analogy.


Unexpected relationship: Megaripples and sand dunes

Foto: Dr. Hezi Yizhaq

These curious “megaripples” resemble large ripples but have long eluded a mechanistic understanding and clear phenomenological characterization. Not surprisingly—the authors say—as they are actually dwarf dunes.

The new perspective might be key to deciphering their morphological long-term memory of ambient soil and weather conditions, and provide interesting new directions for geomorphological analysis and remote sensing applications to related bedforms seen on Mars, for example.

The starting point of the study was a closer look at the conditions under which megaripples form. Turbulent winds not only create sand waves, they also sort grains by size. Fine grains advance quickly while coarser grains trail behind. For this reason, sand found in large dune fields—having been transported for miles by the wind—is typically composed of grains that are all about the same size.

In contrast, megaripples contain grains of all different sizes. Under erosive conditions, the fine grains leave while coarser grains, which are too heavy to be mobilized by the wind, gradually accumulate on the sand bed.

This sets off a special bimodal transport process, in which the impact of high flying fine grains helps the coarse grains to advance in tiny steps. Their drastically reduced hop length prompts a corresponding downsizing of the dunes they form.

As Marc Lämmel et al. now demonstrate, this new interpretation of megaripples as mini-dunes of coarse grains is supported not only by the known co-localization of megaripples and coarse grains. It is quantitatively corroborated by close morphological and dynamical similarities between megaripples and ordinary sand dunes, which had remained unnoticed because of the enormous difference in size.

An important implication of the new work is that megaripples are extraordinarily sensitive to fluctuations in grain-size and wind-strength. It explains why megaripples stop growing during periods of weak winds and quickly erode during storms. What has plagued systematic field studies in the past, now renders megaripples perfect candidates for retrodicting past weather and climate conditions.

How their morphology and grain composition encodes records of past sorting and growth phases reminds one of the growth rings in tree trunks. If judiciously interpreted, petrified or extraterrestrial megripples,
say, will reveal valuable information about the climate history.

While further research is needed to establish a reliable routine for deciphering the messages in the sand, nothing prevents you anymore from embarking on this endeavor yourself, equipped with spade and sieve, on your next beach or desert trip. Before you set off, here is the portable version of the theory for analyzing your data: megaripples are mini-dunes of mega-grains making mini-jumps.

ORIGINAL PUBLICATION:
Marc Lämmel, Anne Meiwald, Hezi Yizhaq, Haim Tsoar, Itzhak Katra, and
Klaus Kroy:

"Aeolian sand sorting and megaripple formation"
Nature Physics (2018) Advance Online Publication (AOP)

Contact:
Prof. Dr. Klaus Kroy
Institute for Theoretical Physics, Leipzig University, Germany
Telefon: +49 341 97-32436
E-Mail: klaus.kroy@itp.uni-leipzig.de

Weitere Informationen:

https://www.nature.com/articles/s41567-018-0106-z

Susann Huster | Universität Leipzig
Further information:
http://www.uni-leipzig.de

More articles from Earth Sciences:

nachricht A promising target in the quest for a 1-million-year-old Antarctic ice core
24.05.2018 | University of Washington

nachricht Tropical Peat Swamps: Restoration of Endangered Carbon Reservoirs
24.05.2018 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>