These images show typical soot superagregattes observed with an electron microscope in wildfire smoke samples collected from three fires in Northern California, New Mexico and Mexico City. Credit: Desert Research Institute
Every year, wildfires clear millions of hectares of land and emit around 34-percent of global soot mass into the atmosphere. In certain regions, such as Southeast Asia and Russia, these fires can contribute as much as 63-percent of regional soot mass.
In a paper published in Nature’s Scientific Reports, a team of scientists led by Rajan Chakrabarty from Nevada’s Desert Research Institute report the observation of a previously unrecognized form of soot particle, identified by the authors as “superaggregates,” from wildfire emissions. These newly identified particles were detected in smoke plumes from wildfires in Northern California, New Mexico, Mexico City, and India.
For several decades, scientists have been trying to quantitatively assess the impacts of wildfire soot particles on climate change and human health. However, due to the unpredictability of wildfire occurrences and the extreme difficulty in sampling smoke plumes in real-time, accurate knowledge of wildfire-emitted soot physical and optical properties has eluded the scientific community.
Unlike conventional sub-micrometer size soot particles emitted from vehicles and cook stoves, superaggregates are on average ten times longer and have a more compact shape. However, these particles have low effective densities which, according to the authors, gives them similar atmospheric long-range transportation and human lung-deposition characteristics to conventional soot particles.
“Our observations suggest that we cannot simply assume a universal form of soot to be emitted from all combustion sources. Large-scale combustion sources, such as wildfires, emit a different form of soot than say, a small-scale, controlled combustion source, such as vehicles.” says Chakrabarty, who also holds a faculty appointment at Washington University in St. Louis.
The study points to the need for revisiting the soot formation mechanism in wildfires, he adds.
The multi-institutional research team first detected the ubiquitous presence of soot superaggregates in smoke plumes from the 2012 Nagarhole National Forest fire in western India.
To verify the presence of superaggregate particles in other fires around the world, the team next analyzed smoke samples collected from the 2010 Millerton Lake fire in Northern California, and the 2011 Las Conchas fire in New Mexico, as well as wildfires near Mexico City. The authors found that a large portion of soot emitted during the flaming phase of these fires were superaggregates.
To assess the potential impact of superaggregates on global climate, scientists also calculated the radiative properties of soot superaggregates using numerically-exact electromagnetic theory.
“We found that superaggregates contribute up to 90-percent more warming than spherical sub-micrometer soot particles, which current climate models use,” said Chakrabarty. “These preliminary findings warrant further research to quantify the significant impact these particles may have on climate, human health, and air pollution around the world.”
New UAlberta assistant professor Alberto Reyes above a glacier at the edge of the Greenland ice sheet. New research by Reyes and colleagues indicates that ice disappeared from most of south Greenland during a long period of warm climate about 400,000 years ago. Credit: Robert Hatfield, Oregon State University
A former University of Alberta PhD student has come back to campus as an assistant professor, to explore and teach about the mysteries of natural climate warming and ice age history, on the heels of a newly published paper in Nature.
Alberto Reyes, an assistant professor in the Faculty of Science who received his PhD from the U of A in 2010, led a study which provides the first scientific evidence that the southern portion of Greenland’s ice sheet nearly disappeared in the geologically recent past, during a long period of warm climate about 400,000 years ago. The findings also indicate that the collapse of the ice sheet, which would have contributed 4.5 to six metres of global sea level rise, likely occurred under conditions that may have been only a few degrees warmer than the present day.
“The study highlights the sensitivity of the ice sheet to small levels of climate warming,” Reyes said.
Reyes, who led the study while at Queen’s University Belfast in collaboration with researchers from the University of Wisconsin-Madison and Oregon State University, spent several years collecting sediment samples from rivers in south Greenland to develop a chemical “fingerprint” of eroded rocks beneath the ice sheet. The group then used that fingerprint to determine when different parts of south Greenland stopped contributing sediment into the ocean.
“This only happens when there is no ice sheet or glacier to erode the rocks at the surface, so the chemistry allows us to broadly track retreat of the ice sheet,” he said.
Their findings indicated a near-complete absence of ice in the region just under a half-million years ago, which indicates the impact of just a small level of climate warming, Reyes noted.
Pointing to recent evidence that the west Antarctic ice sheet has begun collapsing, “This really highlights the sensitivity to the kind of magnitude of climate warming projected over the next several hundred years, so there are long-term consequences,” he added.
Reyes, who researched how permafrost and peatlands responded to past climate warming during his PhD studies at the U of A, will share his knowledge and sense of wonder with students as he teaches second- and third-year courses in global change and ice age history through the environmental earth sciences program.
“During my PhD I had the opportunity to do a lot of fieldwork, which the U of A is really strong in, and I spent a lot of time in the Yukon and Alaska learning about long-term environmental change and interactions between elements of Earth’s systems.
“It’s like history, but with science thrown in, so it’s very interesting.”
Reyes will also continue his research into long-term landscape and environmental change, through his appointment with the Department of Earth and Atmospheric Sciences.
Focused on the Arctic and subarctic regions, Yukon in particular, Reyes’ work will help address “what we might expect from a future warming climate in terms of how things like ice sheets and permafrost will respond.
“I want to understand how interactions between climate, environment and geological processes all work together to shape the landscape we see. The U of A has a strong history as a leader in northern research, so it’s really satisfying to return to the university as an educator and scientist.”
Formula: Fe2TiO5 Environment: Magmatic, post-volcanic or young volcanic rocks. Locality: Vesuvius and Etna, Italy. Name Origin: From the Greek pseudo – “I mislead” and the mineral brookite.
History
Authors (inventeurs) : KOCH Discovery date: 1878 Town of Origin : DEALUL UROIU (ARANYI-HEGY), COMTE DE HUNEDOARA, TRANSYLVANIE Country of Origin : ROUMANIE
Optical properties
Optical and misc. Properties : Translucide – Opaque Refractive Index: from 2,38 to 2,42 Axial angle 2V : 50°
Locations of Antarctic ice core sites used for volcanic sulfate aerosol deposition reconstruction (right); a DRI scientist examines a freshly drilled ice core in the field before ice cores are analyzed in DRI’s ultra-trace ice core analytical laboratory. Credit: M. Sigl
A team of scientists led by Michael Sigl and Joe McConnell of Nevada’s Desert Research Institute (DRI) has completed the most accurate and precise reconstruction to date of historic volcanic sulfate emissions in the Southern Hemisphere.
The new record, described in a manuscript published today in the online edition of Nature Climate Change, is derived from a large number of individual ice cores collected at various locations across Antarctica and is the first annually resolved record extending through the Common Era (the last 2,000 years of human history).
“This record provides the basis for a dramatic improvement in existing reconstructions of volcanic emissions during recent centuries and millennia,” said the report’s lead author Michael Sigl, a postdoctoral fellow and specialist in DRI’s unique ultra-trace ice core analytical laboratory, located on the Institute’s campus in Reno, Nevada.
These reconstructions are critical to accurate model simulations used to assess past natural and anthropogenic climate forcing. Such model simulations underpin environmental policy decisions including those aimed at regulating greenhouse gas and aerosol emissions to mitigate projected global warming.
Powerful volcanic eruptions are one of the most significant causes of climate variability in the past because of the large amounts of sulfur dioxide they emit, leading to formation of microscopic particles known as volcanic sulfate aerosols. These aerosols reflect more of the sun’s radiation back to space, cooling Earth. Past volcanic events are measured through sulfate deposition records found in ice cores and have been linked to short-term global and regional cooling.
This effort brought together the most extensive array of ice core sulfate data in the world, including the West Antarctic Ice Sheet (WAIS) Divide ice core — arguably the most detailed record of volcanic sulfate in the Southern Hemisphere. In total, the study incorporated 26 precisely synchronized ice core records collected in an array of 19 sites from across Antarctica.
“This work is the culmination of more than a decade of collaborative ice core collection and analysis in our lab here at DRI,” said Joe McConnell, a DRI research professor who developed the continuous-flow analysis system used to analyze the ice cores.
McConnell, a member of several research teams that collected the cores (including the 2007-2009 Norwegian-American Scientific Traverse of East Antarctica and the WAIS Divide project that reached a depth of 3,405 meters in 2011), added, “The new record identifies 116 individual volcanic events during the last 2000 years.”
“Our new record completes the period from years 1 to 500 AD, for which there were no reconstructions previously, and significantly improves the record for years 500 to 1500 AD,” Sigl added. This new record also builds on DRI’s previous work as part of the international Past Global Changes (PAGES) effort to help reconstruct an accurate 2,000-year-long global temperature for individual continents.
This study involved collaborating researchers from the United States, Japan, Germany, Norway, Australia, and Italy. International collaborators contributed ice core samples for analysis at DRI as well as ice core measurements and climate modeling.
According to Yuko Motizuki from RIKEN (Japan’s largest comprehensive research institution), “The collaboration between DRI, National Institute of Polar Research (NIPR), and RIKEN just started in the last year, and we were very happy to be able to use the two newly obtained ice core records taken from Dome Fuji, where the volcanic signals are clearly visible. This is because precipitation on the site mainly contains stratospheric components.” Dr. Motizuki analyzed the samples collected by the Japanese Antarctic Research Expedition.
Simulations of volcanic sulfate transport performed with a coupled aerosol-climate model were compared to the ice core observations and used to investigate spatial patterns of sulfate deposition to Antarctica.
“Both observations and model results show that not all eruptions lead to the same spatial pattern of sulfate deposition,” said Matthew Toohey from the German institute GEOMAR Helmholtz Centre for Ocean Research Kiel. He added, “Spatial variability in sulfate deposition means that the accuracy of volcanic sulfate reconstructions depends strongly on having a sufficient number of ice core records from as many different regions of Antarctica as possible.”
With such an accurately synchronized and robust array, Sigl and his colleagues were able to revise reconstructions of past volcanic aerosol loading that are widely used today in climate model simulations. Most notably, the research found that the two largest volcanic eruptions in recent Earth history (Samalas in 1257 and Kuwae in 1458) deposited 30 to 35 percent less sulfate in Antarctica, suggesting that these events had a weaker cooling effect on global climate than previously thought.
Note : The above story is based on materials provided by Desert Research Institute.
Map of the Amazon Basin showing Río Grande (highlighted)
The Río Grande (or Río Guapay) in Bolivia rises on the southern slope of the Cochabamba mountains, east of the city Cochabamba, at 17°26′11″S 65°52′22″W. At its source it is known as the Rocha River. It crosses the Cochabamba valley basin in a westerly direction. After 65 km the river turns south east and after another 50 km joins the Arque River at 17°42′10″S 66°14′45″W and an elevation of 2.350 m.
From this junction the river receives the name Caine River for 162 km and continues to flow in a south easterly direction, before it is called Río Grande. After a total of 500 km the river turns north east and in a wide curve flows round the lowland city of Santa Cruz.
After 1.438 km, the Río Grande joins the Ichilo River at 15°48′09″S 64°43′47″W which is a tributary to the Mamoré.
Note : The above story is based on materials provided by Wikipedia
Chemical Formula: Ag3AsS3 Locality: Himmelsfurst mine, Erbisdor, near Freiberg, Germany Name Origin: After the French chemist, J. L. Proust (1755-1826).
Proustite is a sulfosalt mineral consisting of; silver sulfarsenide, Ag3AsS3, known also as light red silver or ruby silver ore, and an important source of the metal. It is closely allied to the corresponding sulfantimonide, pyrargyrite, from which it was distinguished by the chemical analyses of Joseph L. Proust (1754-1826) in 1804, after whom the mineral received its name.
The prismatic crystals are often terminated by the scalenohedron and the obtuse rhombohedron, thus resembling calcite (dog-tooth-spar) in habit. The color is scarlet-vermilion and the lustre adamantine; crystals are transparent and very brilliant, but on exposure to light they soon become dull black and opaque. The streak is scarlet, the hardness 2.5, and the specific gravity 5.57.
Proustite occurs in hydrothermal deposits as a phase in the oxidized and supergene zone. I is associated with other silver minerals and sulfides such as native silver, native arsenic, xanthoconite, stephanite, acanthite, tetrahedrite and chlorargyrite.
Magnificent groups of large crystals have been found at Chañarcillo in Chile; other localities which have yielded fine specimens are Freiberg and Marienberg in Saxony, Joachimsthal in Bohemia and Markirch in Alsace.
Optical properties
Optical and misc. Properties: Transparent – Translucinte Reflective Power : 28,2-30,3% (580) Refractive Index: from 2,79 to 3,08
Physical properties
Hardness: from 2,00 to 2,50 Density : 5,57 Color : red; cinnabar-red; reddish grey Luster : adamantine; submetallic Streak : brick-red; brownish; pale red Break : conchoidal; irregular Cleavage : yes
Artist’s impression of a massive asteroid impact, such as the one over three billion years ago, that may have splintered Earth’s crust
One of the things that distinguishes Earth from other planets is its plate tectonics. But how did this moving jigsaw surface begin? New research suggests that a 3.26 billion-year-old asteroid impact may have kick-started the process.
The impact crater has long since gone (recycled by plate tectonics), but Norman Sleep and Donald Lowe, both at Stanford University, have been able to study this cataclysmic event by looking at the fall-out it produced: tiny spherical rocks which rained down into an ocean, in what is now South Africa. These little grains, and the shattered rocks surrounding them, tell the story of what was probably one of the last major asteroid impacts during Earth’s violent early history.
And what an impact it was. Hurtling in at 72,000km per hour, this 37km wide asteroid (four times larger than the one that wiped out the dinosaurs) smashed into Earth, vaporising rock and creating a 500km wide crater. The impact triggered magnitude 10.8 earthquakes (100 times larger than the 2011 Japanese earthquake), set off tsunamis, and heated the atmosphere enough to make oceans boil.
Crucially the findings, published in the journal Geochemistry, Geophysics, Geosystems, also indicate that the impact could have initiated plate tectonics. Since then the heat from Earth’s mantle has kept the plates in a state of continuous agitation. Without that impact Earth’s surface might be more akin to Mars or Venus. And without the constant chemical recycling that plate tectonics brings (which stabilises Earth’s climate) we probably wouldn’t be here.
Note : The above story is based on materials provided by Kate Ravilious “The Guardian”
William Philipps, a UB geology graduate researcher, examines Greenland’s terrain as part of research on deglaciation and global climate change. Credit: Jason Briner
After one of the snowiest winters in recent history, William Philipps will forego the beach to spend the summer studying glaciers at the world’s northernmost university.
The University at Buffalo geology graduate student and self-proclaimed “nerd who likes rocks” will travel to the University Centre on Svalbard (UNIS) in Norway to collect data that proves the Svalbard-Barents Sea Ice-Sheet’s (SBSIS) time of deglaciation – the point when the ice began to melt – is older than its suggested age of 12,000 years.
Philipps, an Amherst native, will travel to Svalbard on July 12 through the UNIS’s Icebound Project, funded by the ConocoPhillips and Lundin Petroleum arctic research program, which seeks to improve understanding of the region for petroleum exploration. He will spend three months completing a mix of courses and research on global climate change.
The Norwegian archipelago of Svalbard is not the average study abroad or research experience. Philipps will visit during the region’s midnight sun season, a period when the sun is visible 24 hours a day. He will also undergo survival training that includes strapping on an insulated suit and learning to withstand the chilly artic water.
Fortunately, Philipps is familiar with the experience. A member of the paleoclimatology research group under Jason Briner, PhD, associate professor in the UB Department of Geology in the UB College of Arts and Sciences, he conducted similar research in Greenland as an undergraduate.
“I am incredibly fortunate to be where I am in life,” says Philipps. “I get to work in the most breathtaking settings in the world on complex scientific problems and learn from some of the foremost research scientists in my field.”
At their maximum extent, as long ago as 25,000 years ago, the SBSIS and other ice sheets – some over a mile thick – engulfed the northern hemisphere. But over time, the ice eroded, transporting pieces of rock, known as glacial erratics, up to hundreds of miles into different geologic areas.
Once the ice melted, the rocks were exposed to the sun and bombarded with cosmic radiation, causing a nuclear chemical reaction that produces beryllium. Through cosmogenic exposure dating, researchers measure the ratios of beryllium to determine the time of deglaciation.
The material used to date the SBSIS’s deglaciation were pieces of driftwood found on Kongsøya and Hopen, two of Svalbard’s eastern most islands. However, the conditions for the wood to be deposited on the islands indicate that the time between the ice beginning to drift and when the wood was deposited may be thousands of years off, says Philipps.
After collecting samples from several locations that are fractions of a gram in weight and about the size of a pinhead, the researchers will send the erratics to a mass spectrometer facility to measure their age.
The study’s results will increase the understanding of the SBSIS’s behavior and can potentially help predict the future behavior of the West Antarctic Ice Sheet.
Determining the age of the erratics will also improve constraints of glacial isostatic adjustment (GIA) values for the region, which detail the rise of land masses that were suppressed by the weight of ice sheets during a glacial period, says Philipps.
Note : The above story is based on materials provided by University at Buffalo
Chemical Formula: NaCaB5O7(OH)4·3H2O Locality: Boron, Kern Co., California. Name Origin: Named for Frank H. Probert (1876-1940), University of California, who discovered the mineral.
History
Authors: EAKLE Discovery date : 1929 Town of Origin: MINE BAKER, KRAMER DIST., KERN CO., CALIFORNIE Country of Origin: USA
Optical properties
Optical and misc. Properties: Fragile, cassant – Transparent – Refractive Index : from 1,51 to 1,54 Axial angle 2V: 73°
Physical properties
Hardness : 3,50 Density : 2,14 Color : colorless Luster: vitreous Streak : white Cleavage : yes
Cartoon of the wind intensification/upwelling process. Increasing winds and upwelling may increase nutrients in the lighted upper ocean, enhancing primary productivity, but excessive upwelling may increase turbulence, acidification and de-oxygenation of the photic zone. The ecological impacts of upwelling intensification are difficult to predict. Credit: Steve Ravenscraft for The Pew Charitable Trusts
Summer winds are intensifying along the west coasts of North and South America and southern Africa and climate change is a likely cause, a new study says.
The winds, which blow parallel to the shore and draw cold, nutrient-rich water from the deep ocean to the surface in a process known as coastal upwelling, have increased over the last 60 years in three out of five regions of the world, according to an analysis published Thursday in the journal Science.
Stronger winds have the potential to benefit coastal areas by bringing a surge of nutrients and boosting populations of plankton, fish and other species. But they could also harm marine life by causing turbulence in surface waters, disrupting feeding, worsening ocean acidification and lowering oxygen levels, the study says.
The shift could already be having serious effects on some of the world’s most productive marine fisheries and ecosystems off California, Peru and South Africa.
At this point “we don’t know what the implications are,” said William Sydeman, president of the Farallon Institute for Advanced Ecosystem Research in Petaluma, Calif., who led the study by seven scientists in the U.S. and Australia. “On the one hand it could be good. On the other hand, it could be really bad.”
The windier conditions are occurring in important currents along the eastern edges of the Pacific and Atlantic oceans. In those areas, the influx of nutrients from coastal upwelling fuels higher production of phytoplankton, tiny plant-like organisms that are eaten by fish, which in turn feed populations of seabirds, whales and other marine life.
Scientists said their results lend support to a hypothesis made more than two decades ago by oceanographer Andrew Bakun. He suggested that rising temperatures from the human-caused buildup of greenhouse gases, by causing steeper atmospheric pressure gradients between oceans and continents, would produce stronger winds during summer and drive more coastal upwelling.
To test that claim, researchers reviewed and analyzed 22 published studies that tracked winds in the world’s five major coastal upwelling regions using data from the 1940s to the mid-2000s.
Scientists found a trend of windier conditions in the California Current along the west coast of North America, the Humboldt Current off Peru and Chile and the Benguela Current off the west coast of southern Africa. In the Canary and Iberian currents off northern Africa and Spain, however, they found no clear signs of increasing winds.
Researchers can’t say for sure that human-caused climate change is to blame, but they said finding a pattern that was consistent across several parts of the planet gives a strong indication it is a factor. The study also found that the increase in winds was more pronounced at higher latitudes, which is in line with other observed effects of climate change.
The study’s conclusions are controversial among ocean scientists. They say the records used in the analysis do not go back far enough in time to rule out naturally occurring climate cycles such as the Pacific Decadal Oscillation, which shifts between warm and cool phases about every 20 to 30 years and also influences atmospheric conditions.
“It doesn’t prove that global warming is driving this,” said Art Miller, a climate scientist at Scripps Institution of Oceanography who was not involved in the study.
Similar limitations in the data have made it difficult for other researchers to link increases in coastal upwelling to climate change.
A study published last year by Canadian researchers, for instance, found huge year-to-year changes in coastal winds and the timing and intensity of upwelling from Vancouver Island to Northern California and urged caution in analyzing trends over short time periods.
“We found it extremely difficult to capture a climate change signal,” said Brian Bylhouwer, an environmental scientist with Stantec Consulting in Dartmouth, Canada, who led that study.
Sydeman acknowledged that scientists need more time and data to firmly establish that shifting winds are the result of climate change and not natural cycles.
He said future research will examine the mechanism behind the increase in coastal winds and study how a boost in upwelling might be affecting fish and seabirds off California and South Africa.
More information:
Climate change and wind intensification in coastal upwelling ecosystems, Science 4 July 2014: Vol. 345 no. 6192 pp. 77-80. DOI: 10.1126/science.1251635
Map of the Amazon Basin with the Mamoré River highlighted
The Mamoré is a large river in Bolivia and Brazil, which unites with the Beni to form the Madeira, one of the largest tributaries of the Amazon. It rises on the northern slope of the Sierra de Cochabamba, east of the city of Cochabamba, and is known as the Chimoré down to its junction with the Chapare. Its larger tributaries are the Chapare, Secure, Apere, and Yacuma from the west, and the Ichilo, Guapay, Ivari, Manique, and Guapore from the east.
Taking into account its length only, the Guapay should be considered the upper part of the Mamore; but it is shallow and obstructed, and carries a much smaller volume of water. The Guapore also rivals the Mamore in length and volume, having its source in the Parecis plateau, Mato Grosso, Brazil, a few miles from streams flowing north-ward to the Tapajos and Amazon, and southward to the Paraguay and Paraná rivers. The Mamore is interrupted by rapids a few miles above its junction with the Beni, but a railway 300 km long has been undertaken from below the rapids of the Madeira. Above the rapids the river is navigable to Chimore, at the foot of the sierra, and most of its tributaries are navigable for long distances. In 1874, Franz Keller gave the outflow of the Mamoré at mean water level, and not including the Guapore, as 41,459 cm3/sec (2,530 cub. in. per second), and the area of its drainage basin, also not including the Guapore, as 24,299 km2 (9,382 square miles).
Note : The above story is based on materials provided by Wikipedia
Chemical Formula: Ca2Al2Si3O10(OH)2 Locality: Haslach, Harzburg and Oberstein, Germany. Name Origin: Named after the Dutch Colonel, H. Von Prehn (1733-1785).Prehnite is a inosilicate of calcium and aluminium with the formula: Ca2Al2Si3O10(OH)2. Limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system, and most oftens forms as stalactitic or botryoidal aggregates, with only just the crests of small crystals showing any faces, which are almost always curved or composite. Very rarely will it form distinct, well individualized crystals showing a square-like cross-section, like those found at the Jeffrey Mine in Asbestos, Quebec, Canada. It is brittle with an uneven fracture and a vitreous to pearly lustre. Its hardness is 6-6.5, its specific gravity is 2.80-2.90 and its color varies from light green to yellow, but also colorless, blue or white. In April 2000, a rare orange Prehnite was discovered at the famous Kalahari Manganese Fields in South Africa. It is mostly translucent, and rarely transparent.
Though not a zeolite, it is found associated with minerals such as datolite, calcite, apophyllite, stilbite, laumontite, heulandite etc. in veins and cavities of basaltic rocks, sometimes in granites, syenites, or gneisses. It is an indicator mineral of the prehnite-pumpellyite metamorphic facies.
It was first described in 1788 for an occurrence in the Karoo dolerites of Cradock, Eastern Cape Province, South Africa. It was named for Colonel Hendrik Von Prehn (1733–1785), commander of the military forces of the Dutch colony at the Cape of Good Hope from 1768 to 1780.
Extensive deposits of gem quality prehnite occur in the basalt tableland surrounding Wave Hill Station in the central Northern Territory, of Australia.
History
Authors : WERNER Discovery date : 1788 Town of Origin : CAP DE BONNE ESPERANCE Country of Origin: AFRIQUE DU SUD
Optical properties
Optical and misc. Properties : Macles possibles – Fragile, cassant – Transparent – Translucide – Gemme, pierre fine – Refractive Index : from 1,61 to 1,66 Axial angle 2V: 65-69°
Physical properties
Hardness : from 6,00 to 6,50 Density : from 2,80 to 2,95 Color : yellow; grey; white; colorless; pale green; dark green; green; greenish yellow; yellowish green; pink Luster : vitreous; nacreous Streak: white Break: irregular Cleavage: yes
The new (eleventh) specimen of Archaeopteryx. Credit: H. Tischlinger
Paleontologists of Ludwig-Maximilians-Universitaet (LMU) in Munich are currently studying a new specimen of Archaeopteryx, which reveals previously unknown features of the plumage. The initial findings shed light on the original function of feathers and their recruitment for flight.
A century and a half after its discovery and a mere 150 million years or so since it took to the air, Archaeopteryx still has surprises in store: The eleventh specimen of the iconic “basal bird” so far discovered turns out to have the best preserved plumage of all, permitting detailed comparisons to be made with other feathered dinosaurs. The fossil is being subjected to a thorough examination by a team led by Dr. Oliver Rauhut, a paleontologist in the Department of Earth and Environmental Sciences at LMU Munich, who is also affiliated with the Bavarian State Collection for Paleontology and Geology in Munich. The first results of their analysis of the plumage are reported in the latest issue of Nature. The new data make a significant contribution to the ongoing debate over the evolution of feathers and its relationship to avian flight. They also imply that the links between feather development and the origin of flight are probably much more complex than has been assumed up to now.
“For the first time, it has become possible to examine the detailed structure of the feathers on the body, the tail and, above all, on the legs,” says Oliver Rauhut. In the case of this new specimen, the feathers are, for the most part, preserved as impressions in the rock matrix. “Comparisons with other feathered predatory dinosaurs indicate that the plumage in the different regions of the body varied widely between these species. That suggests that primordial feathers did not evolve in connection with flight-related roles, but originated in other functional contexts,” says Dr. Christian Foth of LMU and the Bavarian State Collection for Paleontology and Geology in Munich, first author on the new paper.
To keep warm and to catch the eye
Predatory dinosaurs (theropods) with body plumage are now known to predate Archaeopteryx, and their feathers probably provided thermal insulation. Advanced species of predatory dinosaurs and primitive birds with feathered forelimbs may have used them as balance organs when running, like ostriches do today. Moreover, feathers could have served useful functions in brooding, camouflage and display. Indeed, the feathers on the tail, wings and hind-limbs most probably fulfilled functions in display, although it is very likely that Archaeopteryx was also capable of flight. “Interestingly, the lateral feathers in the tail of Archaeopteryx had an aerodynamic form, and most probably played an important role in its aerial abilities,” says Foth.
On the basis of their investigation of the plumage of the new fossil, the researchers have been able to clarify the taxonomical relationship between Archaeopteryx and other species of feathered dinosaur. Here, the diversity in form and distribution of the feather tracts is particularly striking. For instance, among dinosaurs that had feathers on their legs, many had long feathers extending to the toes, while others had shorter down-like plumage. “If feathers had evolved originally for flight, functional constraints should have restricted their range of variation. And in primitive birds we do see less variation in wing feathers than in those on the hind-limbs or the tail,” explains Foth.
These observations imply that feathers acquired their aerodynamic functions secondarily: Once feathers had been invented, they could be co-opted for flight. “It is even possible that the ability to fly evolved more than once within the theropods,” says Rauhut. “Since the feathers were already present, different groups of predatory dinosaurs and their descendants, the birds, could have exploited these structures in different ways.” The new results also contradict the theory that powered avian flight evolved from earlier four-winged species that were able to glide.
Archaeopteryx represents a transitional form between reptiles and birds and is the best-known, and possibly the earliest, bird fossil. It proves that modern birds are directly descended from predatory dinosaurs, and are themselves essentially modern-day dinosaurs. The many new fossil species of feathered dinosaurs discovered in China in recent years have made it possible to place Archaeopteryx within a larger evolutionary context. However, when feathers first appeared and how often flight evolved are matters that are still under debate.
The eleventh known specimen of Archaeopteryx is still in private hands. Like all other examples of the genus, it was found in the Altmühl valley in Bavaria, which in Late Jurassic times lay in the northern tropics, and at the bottom of a shallow sea, as all Archaeopteryx fossils found so far have been recovered from limestone deposits.
Note : The above story is based on materials provided by Ludwig-Maximilians-Universitaet Muenchen (LMU).
Scientists at Rice have reported the results of their decadelong effort to build a two-dimensional mathematical model that will help identify rich pockets of gas hydrate under the ocean floor. The model shows where hydrates – the “ice that burns” – are likely to be found based on extrapolating data from core samples, seismic signals and other geologic data. Click for larger image. Credit: Sayantan Chatterjee
A decade of research by Rice University scientists has produced a two-dimensional model to prove how gas hydrate, the “ice that burns,” is formed under the ocean floor.Gas hydrate—basically methane frozen under high pressures and low temperatures—has potential as a source of abundant energy, if it can be extracted and turned into usable form.
It also has potential to do great harm, if global warming results in melting hydrate that releases methane, a powerful greenhouse gas, into the atmosphere.
The award-winning mathematical model created by Rice alumnus Sayantan Chatterjee, who earned his doctorate in chemical engineer George Hirasaki’s group, is intended to help pinpoint abundant pockets of hydrate by extrapolating data from several sources: one-dimensional core samples, seismic surveys that image the fractures as well as stratified layers of sand and clay that build up over millennia, and the geochemistry of sediment and water near the ocean floor, which offers chemical clues to what lies beneath.
The research was published by the Journal of Geophysical Research – Solid Earth.
There’s a lot at stake for energy producers—and consumers—in finding hydrates in high concentrations, with as much as 20 trillion tons of methane under the sea. Japanese researchers are already testing production techniques in the Pacific, but extraction without reliable exploration tools is too expensive, Chatterjee said.
The Rice researchers’ two-dimensional model draws upon a variety of survey techniques to envision a more accurate slice of the deep-sea formation.
“Our modeling incorporates geologic processes like sedimentation and compaction that enable methane-rich fluids to flow through porous media,” Chatterjee said. Methane degraded by microbes from organic matter or rising from the depths turns into hydrate when it encounters the necessary pressure, temperature and salinity conditions in the gas hydrate stability zone, which can be as shallow as a few hundred meters.
“High-saturation hydrate deposits preferentially occur in fracture networks within fine-grained sediment and interbedded, permeable sand sequences, and we’re looking for such lithologic sweet spots,” he said.
Chatterjee explained the complex stratigraphy and lack of homogeneity of subsea formations limits the ability of one-dimensional modeling and core samples to scan a potential hydrate reservoir isolated in permeable sand sequences between dense layers of clay. “Marine lithologic layering is very complex, and we can’t replicate it in our models. But we have developed techniques to compute local fluid flow in lithologically complex reservoirs, which we correlate to local hydrate saturation,” he said.
“When people seismically image the submarine formations and recover sediment cores dominated with faults and fractures, they find these fractures to be filled with hydrates,” Chatterjee said. “Our model has explained this observation. It shows that these fracture networks and sand layers are the sweet spots for hydrate occurrence, the ones we want to pinpoint when it comes to exploration.”
The Rice team intends the model to locate these hydrate-rich pockets and estimate how saturated they’re likely to be based on the geologic setting and history. “Only when a pore space is highly saturated with hydrate is it economically feasible to drill at that location to extract these trapped hydrocarbons,” he said. “But first we have to estimate the fluid flow. No flow, no hydrates.”
More information:
Sayantan Chatterjee, Gaurav Bhatnagar, Brandon Dugan, Gerald R. Dickens, Walter G. Chapman and George J. Hirasaki “The Impact of Lithologic Heterogeneity and Focused Fluid Flow upon Gas Hydrate Distribution in Marine Sediments” Journal of Geophysical Research: Solid Earth. Accepted manuscript online: 25 JUN 2014 DOI: 10.1002/2014JB011236
Note : The above story is based on materials provided by Rice University
Chemical Formula: Ca(MoO4) Locality: Peacock Mine, Cuprum, Seven Devils District, Adams Co., Idaho, USA Name Origin: Named after the American geologist, John Westly Powell (1834-1902).Powellite is a calcium molybdate mineral with formula Ca(MoO4). Powellite crystallizes with tetragonal – dipyramidal crystal structure as transparent adamantine blue, greenish brown, yellow to grey typically anhedral forms. It exhibits distinct cleavage and has a brittle to conchoidal fracture. It has a Mohs hardness of 3.5 to 4 and a specific gravity is 4.25. It forms a solid solution series with scheelite (calcium tungstate, CaWO4). It has refractive index values of nω=1.974 and nε=1.984.Powellite was first described by William Harlow Melville in 1891 for an occurrence in the Peacock Mine, Adams County, Idaho and named for American explorer and geologist, John Wesley Powell (1834–1902).
It occurs in hydrothermal ore deposits of molybdenum within the near surface oxidized zones. It also appears as a rare mineral phase in pegmatite, tactite and basalt. Minerals found in association with powellite include molybdenite, ferrimolybdite, stilbite, laumontite and apophyllite.
History
Authors: MELVILLE Discovery date : 1891 Town of Origin : PEACOCK CLAIM, SEVEN DEVILS DIST., ADAMS CO., UTAH Country of Origin: USA
Optical properties
Optical and misc. Properties: Transparent – fluorescent Refractive Index: from 1,96 to 1,97
Physical properties
Hardness : from 3,50 to 4,00 Density : 4,23 Color : yellow; greenish yellow; greenish; brown; grayish; white; blue; blackish blue; grey; greenish blue Luster : sub-adamantine; greasy; nacreous Streak: pale yellow; greenish; grey white Break: irregular Cleavage: yes
A team of scientists has discovered that a giant ‘burp’ of carbon dioxide (CO2) from the North Pacific Ocean helped trigger the end of last ice age, around 17,000 years ago.
A recent study, led by Dr James Rae of the University of St Andrews, found that changes in ocean circulation in the North Pacific caused a massive ‘burp’ of CO2 to be released from the deep ocean into the atmosphere, helping to warm the planet sufficiently to trigger the end of the ice age.
Previously, scientists have suggested that the Antarctic Ocean and North Atlantic were the only places likely to release deglacial CO2, due to their deep water formation. However, a change in rainfall over the North Pacific region, caused by the East Asian monsoon and the Westerly storm track, made the ocean surface saltier and less buoyant, allowing it to form deep water. This allowed CO2 stored in the deep Pacific to be released to the atmosphere, where it helped warm the planet and melt back the ice sheets that covered much of the Northern Hemisphere.
Dr James Rae, of the University’s Department of Earth and Environmental Sciences, explained:
“Our study shows that North Pacific deep water penetrated all the way into the deep ocean, allowing it to release deep ocean CO2. We tested this idea further with a climate model, which showed that deep water formation in the North Pacific causes ocean CO2 release, large enough to drive the atmospheric CO2 rise recorded at the start of the deglaciation.
The results of our study came as a big surprise, as we were expecting to see a signature of CO2 release from the ocean around Antarctica, which has been the leading hypothesis for deglacial CO2 rise. Instead we found a signal we can only explain with CO2 release from the North Pacific.”
The team of scientists from the University of St Andrews, University of Bristol and University of Kiel, Germany, made a series of chemical measurements on minuscule fossil shells to trace ocean CO2 storage and circulation patterns up to two miles beneath the ocean’s surface.
Dr Gavin Foster, of the University of Southampton, added; “This study is only really possible thanks to new developments in geochemistry, that allow us to reconstruct the pH of the ocean in the past for the first time, giving an accurate measurement of how ocean CO2 is stored and released”.
The new findings will help scientists understand how the earth’s climate can operate, and the different ways in which the ocean and atmosphere can exchange CO2.
Dr Rae concluded:
“Although the CO2 rise caused by this process was dramatic in geological terms, it happened very slowly compared to modern man-made CO2 rise. Humans have driven CO2 rise in the atmosphere as large as the CO2 rise that helped end the last ice age, but the man-made CO2 rise has happened 100 times faster. This will have a huge effect on the climate system, and one that we are only just starting to see.”
More information:
Rae, J. W. B., M. Sarnthein, G. L. Foster, A. Ridgwell, P. M. Grootes, and T. Elliott (2014), “Deep water formation in the North Pacific and deglacial CO2 rise,” Paleoceanography, 29, DOI: 10.1002/2013PA002570.
Note : The above story is based on materials provided by University of St Andrews
Iron is an essential element in all living creatures, and its availability in seawater can have a profound effect on phytoplankton growth and, consequently, the earth’s carbon cycle. In the journal Nature, Seth John and Tim Conway have just published an assessment of the various sources of dissolved iron in the north Atlantic Ocean.
Iron is present in tiny concentrations in seawater. On the order of a few billionths of a gram in a liter.
“I did a calculation once on a ton of ocean water,” says Seth John, an assistant professor in the department of marine science at the University of South Carolina. “The amount of iron in that ton of water would weigh about as much as a single eyelash.”
Given that there is so little iron in seawater, one might conclude that its presence there is inconsequential.
Hardly. Iron is one of the essential elements of life. Found in enzymes like myoglobin and hemoglobin and cytochrome P450, iron is an essential cog in the biomachinery of every living cell. And its scarcity in the ocean, the earth’s wellspring of life, only magnifies its importance.
“The key reason that everybody cares about iron is because it limits the growth of phytoplankton, such as algae, in maybe a fifth of the ocean,” says John, a researcher in the School of Earth, Ocean and Environment in South Carolina’s College of Arts and Sciences.
In those iron-poor places, there’s plenty of everything else that phytoplankton, the base of the food web, need to grow—sunlight, carbon, fixed nitrogen, water. Just a small change in the amount of iron that finds its way there can have a dramatic impact on the growth of photosynthetic organisms and their concomitant uptake of carbon dioxide.
When algae and other phytoplankton grow, they take carbon dioxide out of the atmosphere, converting it into proteins and other carbon-based molecules that constitute living cells. And it takes very little iron to keep this process going—in a typical cell, for every atom of iron, there are about a million atoms of carbon, says John. A little iron goes a long way in allowing phytoplankton to grow and pull carbon dioxide out of the air.
Knowing how iron moves into the oceans is thus crucial for scientists to fully understand the details of the carbon cycle on earth.
John and his colleagues have spent the past several years working to fill in those details. They’ve been collecting ocean samples and developing their analytical techniques for quantifying different natural isotopes of iron in seawater, which is one means of tracking the origins of the dissolved metal.
Iron finds its way into seawater from a variety of sources. The ratio of the stable natural isotopes iron-56 and iron-54 from these sources can differ from the ratio in the earth’s crust because a number of chemical processes change the ratio by favoring the release of one of the two isotopes. The processes controlling release of iron from distinct sources vary, and so different sources can have characteristic iron-56/iron-54 ratios. Tiny variations in this ratio in seawater samples thus provide insight into the origin of the iron found there.
For example, one source is sediments from the ocean’s floor, from which iron is typically released into the ocean under very low-oxygen (anoxic) conditions, and release of ‘light’ iron-54 is favored. Another source is dust from the atmosphere, from which Fe is typically released into the ocean with processes favoring ‘heavy’ iron-56. Using this information, the researchers were able to establish, for the first time, where dissolved iron in seawater had originated.
John and postdoctoral associate Tim Conway have developed a high-throughput means of purifying seawater samples and determining the iron-56/iron-54 ratio, a method capable of handling the nearly 600 samples they collected in a high-resolution transect of the north Atlantic Ocean on a GEOTRACES cruise.
From those samples, they were able to show in a paper published in the journal Nature that the largest source of iron in the north Atlantic, somewhere between 70 and 90 percent, comes from dust that blows in from the Sahara desert.
The results are helping define a very poorly understood but essential component of the carbon cycle.
“It could help us understand past climate change, like glacial-interglacial cycles,” says John. “There would have been huge changes in dust fluxes to the ocean in glacial times, and so understanding how much iron comes from dust in the modern day helps us figure out whether that was an important driver of glacial-interglacial cycles.”
The breakdown of the sources might surprise many, according to John and Conway.
“I think that a lot of people thought that there would be a lot of dust in the north Atlantic, and so while it’s very satisfying to have proved that, it’s perhaps more surprising that there’s 20 percent that comes from other sources,” says John. “I think before we published this paper, you would have found many, many people who would have guessed that that was zero percent or very close to zero percent.”
“That’s one interesting thing that the iron isotopes really show on the east margin,” says Conway. “Off the coast of Africa you have really high iron, and in the past most people attributed that just to dust. We can show from the iron isotopes that there’s actually iron coming from sediments.
“People have always argued whether it was dust or sediments. This is one of the first studies to really show clearly that sediments are important as well.”
Chemical Formula: KNa2B3Si12O30 Locality: From Mont Saint-Hilaire, Quebec, Canada. Name Origin: Named for the Poudrette family, operators of the quarry where type material was discovered.
Poudretteite is an extremely rare mineral and gemstone that was first discovered as minute crystals in Mont St. Hilaire, Quebec, Canada, during the 1960s. The mineral was named for the Poudrette family because they operated a quarry in the Mont St. Hilaire area where poudretteite was originally found.
History
Discovery date : 1987 Town of Origin : MONT SAINT-HILAIRE, ROUVILLE CO., QUEBEC Country of Origin: CANADA
Physical properties
Hardness : 5,00 Density : 2,51 Color : colorless; pale pink Luster : vitreous Streak: white Break : conchoidal; splintery Cleavage : NO
When the 1893 World’s Fair opened in Chicago, fairgoers aboard the world’s first Ferris wheel soared high enough to compare two cities: the White City—gleaming whitewashed architecture built for the massive fair—and its dark twin, the blackened, soot-stained buildings of the Loop just a few miles to the north.
Chicago, like many industrialized cities in the 19th century, lay under a thick layer of soot of its own making. Dirt from trains and factories soiled linen shirts and blew into homes past tightly shut windows. Across the Atlantic in London, residents lit lamps at midday to wade through pea-soup fogs, yellow with sulfur, that lingered over the city for days.
Nineteenth-century meteorologist Luke Howard called London “the volcano of a hundred thousand mouths,” referring to the city’s factories and engines that constantly exhaled soot, which is mostly made up of tiny particles of black carbon. Black carbon is released when things burn: coal and other fuels, bush fires, and the combustion that powers diesel engines and generators.
In the 20th century, scientists began to learn exactly how bad soot is for human health—it accelerates heart failure and burrows into lung tissue, aggravating asthma and respiratory conditions. More recently, scientists have started to realize that carbon particulates play a second unwelcome role: the second largest contributor to climate change.
Environmental regulations have helped to clear the skies over many cities. Yet the U.S., along with other countries around the world, still releases particles of carbon from trucks and generators, and we still don’t really understand what happens to it once it leaves the exhaust pipe.
But there is one bright spot in the study of soot. Unlike carbon dioxide, which will remain for hundreds of years, it can cycle out of the atmosphere within weeks. Whatever harm carbon particulates do to the atmosphere is temporary, at least theoretically. That is, if we could only stop.
“Changing habits is perhaps the most difficult challenge of all,” said Argonne scientist Rao Kotamarthi.
Carbon dioxide has long been established as the most notorious contributor to climate change. But aerosolized carbon particles floating around in the atmosphere also influence climate, although their combined effect is substantially more complex. For example, aerosols can scatter incoming solar radiation away from Earth—fling it back into space—which cools the Earth. Or they can absorb solar radiation, which contributes to global warming.
Though they by and large tend to absorb heat, carbon particles are big enough to serve as nuclei for cloud formation. And clouds reflect more sunlight, which cools the Earth. However, there’s some evidence that clouds formed around black carbon don’t last as long; the dark nucleus absorbs heat and evaporates the cloud.
Researchers try to understand this massive puzzle by building extremely detailed virtual models of the atmosphere. At Argonne, climate scientists like Yan Feng pack all the data they can get their hands on into an elaborate working picture of the atmosphere and how it behaves.
To make sure that the model’s analyses line up with the real world, scientists go through a process called “ground-truthing.” “We compare our model’s results to measurements taken at actual sites and see how they compare,” Feng said.
Once they know the model is reliable, Feng and her colleagues can run models forward in time to see what might happen in 10, 25, 100 years, depending on whether we cut aerosol emissions or let them run wild.
“It’s an extremely complex puzzle, but we can address it by looking carefully at problems one by one,” said Rao Kotamarthi, who manages a climate modeling program at Argonne.
Carbon aerosols are in some ways more difficult to model than carbon dioxide. Whereas carbon dioxide spreads fairly evenly around the world, black carbon tends to affect weather more locally. Carbon particulates often linger in the same region where they are emitted because the particles are too heavy to mix into the atmosphere but not as easily washed out in raindrops as other aerosols. A lot of carbon aerosol modeling, therefore, relies heavily on meteorology: charting the local ebb and flow of wind and water and temperature to map how the particles travel. “For example, large-scale meteorology, like a big cold front, can wipe out some of the carbon’s effects—but not all,” Feng said.
In the past few years, Feng has turned her attention to a second type of carbon in the atmosphere, called brown carbon. These are organic particles with different chemical compositions; they can be tar balls or fats. Long, smoldering fires give off brown carbon; hot fires release black.
There’s a lot more brown carbon in the atmosphere by mass, but it can’t trap as much heat by mass as black carbon—”Think of wearing a black shirt in the sun,” Kotamarthi said—so it’s largely been overlooked.
Only recently have researchers at Argonne and elsewhere begun to explore brown carbon’s effects and habits more closely. “We have a little idea of how black carbon behaves,” Feng said. “But brown carbon was only identified as a potentially significant factor in the past several years.”
Feng, along with Kotamarthi and Professor V. Ramanathan at the Scripps Institution of Oceanography, recently published the first global model study to estimate how much heat brown carbon traps in the atmosphere. “Our model shows how carbon is distributed across the atmosphere,” she said. “We can use that to predict how much solar radiation is being trapped in the atmosphere, and from that we can estimate how much the global temperature may rise.” Feng thinks that brown carbon could turn out to be a significant factor in how aerosols affect Earth’s climate.
There are still a lot of uncertainties in the model, though. “Getting more data is the biggest problem,” Kotamarthi said.
That’s where Argonne environmental scientist David Streets comes in. Streets specializes in collecting data on emissions; he modeled Beijing’s air quality before it hosted the 2008 Summer Olympics. In 2005, along with Professor Tami Bond of the University of Illinois, he published the gold standard figures for soot sources now used by modelers around the world.
“We tell them what’s being emitted into the air,” Streets said. “They use meteorology to get where it winds up and how it affects weather and climate.”
To ensure the accuracy of his data, Streets works with collaborators all over the world, including rapidly industrializing countries like China and India.
Climate modelers also keep an eye on a number of different global economic indicators, because the health of the world’s economies significantly affects emissions. In 2008, scientists saw the economic crash written out in the sky. Aerosols dropped noticeably. The skies cleared over Greece in 2010 as the debt crisis squeezed its citizens below.
This is a central reason why aerosol emissions control is so hard. Carbon, like carbon dioxide, tends to ride piggyback on economic development. In particular, developing countries—where the electricity sometimes goes out because the power infrastructure hasn’t quite kept up with demand—tend to rely heavily on diesel generators. They produce a lot of black carbon.
And aerosols are a major human health problem in developing countries. The World Health Organization puts smoke from solid fuels as the 10th major mortality risk factor globally; it estimates that smoke contributes to approximately two million deaths annually, particularly affecting women and children. Urban air pollution ranks among the top 10 risk factors in middle and developed countries too.
We’ve succeeded in reducing emissions from factories and other sources in developed countries like the U.S. and Europe; in many places, black carbon emission levels are lower than they’ve been in decades, if not centuries. In Chicago, cleaners scrubbed a century’s worth of soot off several buildings in the Loop to discover stone and brick underneath in shades of delicate pastels that probably hadn’t been seen since the last tourists left the World’s Fair more than 100 years ago.
“Purely from a technical standpoint, we could do this,” Streets said. “We have the technology.”
Note : The above story is based on materials provided by Argonne National Laboratory
Soot, a.k.a. black carbon, is finding its way to snow-covered peaks and glaciers around the world. Primarily the result of particulate emissions from burning fossil fuels, such as coal-fired power plants and diesel engines, soot has an impact on the regional and global climate. In the Arctic, soot increases ice and snow melt, causing a series of events that are heating up the climate.
No one but a Grinch enjoys black snow—it has no redeeming qualities. Yet scientists at Pacific Northwest National Laboratory trained their sights on soot to understand its undesirable effects on the Arctic environment. Using global climate model simulations, they evaluated soot’s effects in Northern China and the Arctic against measurements over the region. PNNL and a University of Michigan collaborator found key model parameters that correctly spot soot buildup and melt-away in a complex seasonal and latitudinal dependence swing. Their study will help the climate modeling community better understand soot’s great influence on regional and global climate.
Soot, a.k.a. black carbon, may have a greater impact on the fast-retreating Arctic snow pack and glaciers than any other human-caused climate-warming agent. Soot is black, and black draws and holds heat from the sun. Soot from combustion of fossil fuels, such as diesel and coal, as well as forest fires and other organic burning, travels through the atmosphere and falls on snow and glacier ice pack. Like a dark blanket, it heats up the snow and ice and also reduces the amount of the sun’s rays normally reflected back into space from bright, white snow. It’s a one-two punch for the world’s store of ice and snow. This study helps researchers understand how black carbon’s impacts are registered and reproduced in climate models, providing valuable information in predicting the future of the Arctic climate.
The research team led by Dr. Yun Qian at PNNL evaluated the simulated black carbon on snow against measurements collected from multiple field campaigns over the Arctic and Northern China. They conducted a series of sensitivity experiments using the newly improved Community Atmosphere Model version 5 (CAM5) to examine the impact of several key parameters. They looked at the impact of snow aging, and the melt-water scavenging efficiency parameters on black carbon’s concentration and radiative forcing in the model. They also compared the uncertainty (the range of possible answers), resulting from the black carbon deposition, with the uncertainty related to how snow-aging and melt-water scavenging is treated for black carbon in the model.
The sensitivity simulations in CAM5 indicated that the melt-water scavenging efficiency parameter plays an important role in regulating black carbon concentrations in the Arctic through the post-depositional enrichment, which not only drastically changes the amplitude but also shifts the seasonal cycle of the black carbon in snow concentration and its radiative forcing in the Arctic. They found that the improvements of black carbon transport and deposition in CAM5 have a stronger influence on black carbon in snow than perturbations of the two snow model parameters over Northern China.
Scientists are planning research that will explore the limitations of simulating black carbon in snow that were highlighted in this study, including in situ observations and laboratory studies with a focus on snow aging and melt-water scavenging of black carbon.
More information:
Qian Y, H Wang, R Zhang, M Flanner, and PJ Rasch. 2014. “A Sensitivity Study on Modeling the Black Carbon in Snow and its Radiative Forcing over the Arctic and Northern China.” Environmental Research Letters 9:064001. DOI: 10.1088/1748-9326/9/6/064001
Note : The above story is based on materials provided by Pacific Northwest National Laboratory
