CU-Boulder physics Assistant Professor Meredith Betterton said the spikes, known as penitentes, are shaped when concentrated rays of sunlight evaporate snow from low spots on glacier fields in a process known as sublimation. The lab studies confirm that the low spots, or troughs, deepen as intense sunlight strikes them, sculpting penitentes by the hundreds of thousands on some glaciers, she said.
Some scientists have predicted that penitentes might help put the brakes on shrinking glaciers in a warming climate by blocking sunlight that might otherwise be absorbed by glacial surfaces, said Betterton. She gave a presentation on penitentes at the March Meeting of the American Physical Society in Denver March 5-9, which hosted more than 7,000 scientists.
"The key piece of physics here is that the dips in the snow absorb more reflected light, which drops the snow height and helps to form the penitentes," she said. "One big question is how penitentes will fare in a warming world."
Betterton, along with colleagues Vance Bergeron and Charles Berger from Ecole Normale Superieure research laboratories in Paris, sprouted miniature penitentes in the lab to better understand the physics behind their formation. Penitentes -- named for their resemblance to a procession of white-hooded monks -- were first described by naturalist Charles Darwin during an expedition to South America he and his crew made in 1835 aboard his ship, the Beagle.
The research team put a block of snow in a horizontal freezer in Paris filled with water vapor and chilled with liquid nitrogen, covered it with a clear Plexiglas lid, and shined a spotlight on the snow to simulate sunlight, Betterton said. Tiny snow spikes up to two inches high formed within a few hours, apparently by the same process through which penitentes form naturally on alpine glaciers, she said.
The study confirmed previous theories that penitentes grow when sunlight in cold, dry air in the high mountains strikes snow patches and transforms them directly into water vapor, she said. Mathematical models developed by Betterton indicate microscopic penitentes begin merging with each other, or "coarsening," early in the sublimation process, growing both taller and wider over time.
The research has applications for understanding and even mitigating global warming, since Andean penitentes shade large areas of glacial surfaces, possibly cooling them and slowing the rate of ice loss, she said. Some scientists believe warming temperatures could trigger the eventual destruction of vast fields of penitentes and hasten glacier melting, "which would be disastrous for Argentinean and Chilean regions that depend on runoff for water supplies," said Betterton.
Betterton and her colleagues took the research a step further, sprinkling the sprouting lab penitentes with a fine layer of carbon soot to simulate pollutants known to be accumulating on some glaciers around the globe. Such carbon-based pollutants have been found to increase melting rates on glaciers by causing the ice to absorb more sunlight and heat up, she said.
The team found that small amounts of soot sprinkled on the snow in the lab appeared to accelerate penitente formation. "One worry that scientists have is that without penitentes, some of these Andean glaciers will melt more quickly," she said. "It may well be that adding a small layer of dirt to the surface of these glaciers could help to preserve them."
The penitente research effort also has implications for the microelectronic industry, she said. Precisely shaped micro-penitentes formed by laser beams could lead to the development of solar energy cells that trap light more efficiently.
Meredith Betterton | EurekAlert!
NASA examines Peru's deadly rainfall
24.03.2017 | NASA/Goddard Space Flight Center
Steep rise of the Bernese Alps
24.03.2017 | Universität Bern
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...
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...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
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...
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...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy