Level of important greenhouse gas has stopped growing

Level of important greenhouse gas has stopped growing

 

Level of important greenhouse gas has stopped growing

Scientists at UC Irvine have determined that levels of atmospheric methane -- an influential greenhouse gas -- have stayed nearly flat for the past seven years, which follows a rise that spanned at least two decades.

This finding indicates that methane may no longer be as large a global warming threat as previously thought, and it provides evidence that methane levels can be controlled. Scientists also found that pulses of increased methane were paralleled by increases of ethane, a gas known to be emitted during fires. This is further indication that methane is formed during biomass burning, and that large-scale fires can be a big source of atmospheric methane.

Professors F. Sherwood Rowland and Donald R. Blake, along with researchers Isobel J. Simpson and Simone Meinardi, believe one reason for the slowdown in methane concentration growth may be leak-preventing repairs made to oil and gas lines and storage facilities, which can release methane into the atmosphere. Other reasons may include a slower growth or decrease in methane emissions from coal mining, rice paddies and natural gas production.

"If one really tightens emissions, the amount of methane in the atmosphere 10 years from now could be less than it is today. We will gain some ground on global warming if methane is not as large a contributor in the future as it has been in the past century," said Rowland, Donald Bren Research Professor of Chemistry and Earth System Science, and co-recipient of the 1995 Nobel Prize for discovering that chlorofluorocarbons in products such as aerosol sprays and coolants were damaging the Earth's protective ozone layer.

The methane research will be published in the Nov. 23 online edition of Geophysical Research Letters.

Methane, the major ingredient in natural gas, warms the atmosphere through the greenhouse effect and helps form ozone, an ingredient in smog. Since the Industrial Revolution in the late 1700s, atmospheric methane has more than doubled. About two-thirds of methane emissions can be traced to human activities such as fossil-fuel extraction, rice paddies, landfills and cattle. Methane also is produced by termites and wetlands.

Scientists in the Rowland-Blake lab use canisters to collect sea-level air in locations from northern Alaska to southern New Zealand. Then, they measure the amount of methane in each canister and calculate a global average.

>From December 1998 to December 2005, the samples showed a near-zero growth of methane, ranging from a 0.2 percent decrease per year to a 0.3 percent gain. From 1978 to 1987, the amount of methane in the global troposphere increased by 11 percent – a more than 1 percent increase each year. In the late 1980s, the growth rate slowed to between 0.3 percent and 0.6 percent per year. It continued to decline into the 1990s, but with a few sharp upward fluctuations, which scientists have linked to non-cyclical events such as the eruption of Mt. Pinatubo in 1991 and the Indonesian and boreal wildfires in 1997 and 1998.

Along with methane, the UCI scientists also measured levels of other gases, including ethane, a by-product of petroleum refining that also is formed during biomass burning, and perchloroethylene, a chlorinated solvent often used in the dry cleaning process. Ethane levels followed the peaks and valleys of methane over time, but perchloroethylene had a different pattern. This finding provides evidence that biomass burning on occasion, as in Indonesia in 1997 and Russia in 1998, can be a large source of atmospheric methane.

The researchers say there is no reason to believe that methane levels will remain stable in the future, but the fact that leveling off is occurring now indicates that society can do something about global warming. Methane has an atmospheric lifetime of about eight years. Carbon dioxide – the main greenhouse gas that is produced by burning fossil fuels for power generation and transportation – can last a century and has been accumulating steadily in the atmosphere.

"If carbon dioxide levels were the same today as they were in 2000, the global warming discussion would leave the front page. But to stabilize this greenhouse gas, we would have to cut way back on emissions," Rowland said. "Methane is not as significant a greenhouse gas as carbon dioxide, but its effects are important. The world needs to work hard to reduce emissions of all greenhouse gases."

NASA and the Gary Comer Abrupt Climate Change Fellowship supported this research.

>From UC Irvine

Humpback whales have brain cells also found in humans

Humpback whales have brain cells also found in humans

Humpback whales have brain cells also found in humans

 

Cetaceans, the group of marine mammals that includes whales and dolphins, have demonstrated remarkable auditory and communicative abilities, as well as complex social behaviors. A new study published online November 27, 2006 in The Anatomical Record, the official journal of the American Association of Anatomists,compared a humpback whale brain with brains from several other cetacean species and found the presence of a certain type of neuron cell that is also found in humans. This suggests that certain cetaceans and hominids may have evolved side by side. The study is available online via Wiley InterScience at http://www.interscience.wiley.com/journal/ar.

Although the biology of the humpback whale is well understood, there have been virtually no studies published on its brain composition, leaving an open question as to how brain structure may relate to the extensive behavioral and social abilities of this mammal. Although brain to body mass ratio, a rough measure of intelligence, is lower for baleen whales such as the humpback compared to toothed whales such as dolphins, the structure and large brain size of baleen whales suggests that they too have a complex and elaborate evolutionary history.

Patrick R. Hof and Estel Van der Gucht of the Department of Neuroscience at Mount Sinai School of Medicine in New York, NY, examined the brain of an adult humpback whale and compared it with the brain of a fin whale (another baleen species) and brains from several toothed whales, including three bottlenose dolphins, an Amazon river dolphin, a sperm whale, two beluga whales, a killer whale and several other whale and dolphin species. They found that the humpback cerebral cortex, the part of the brain where thought processes take place, was similar in complexity to smaller sized cetaceans such as dolphins. The large area of cortex found in these mammals is thought to be related to acoustic capabilities and the current study shows that it is organized into a system of core and belt regions. However, substantial variability was found between the cell structure of the cortex in humpbacks compared to toothed whales. The authors suggest that these differences may indicate differences in brain function and behavior in aquatic species that are not yet understood.

One feature that stood out in the humpback whale brain was the modular organization of certain cells into "islands" in the cerebral cortex that is also seen in the fin whale and other types of mammals. The authors speculate that this structural feature may have evolved in order to promote fast and efficient communication between neurons. The other notable feature was the presence of spindle cells in the humpback cortex in areas comparable to hominids and in other areas of the whale brain as well. Although the function of spindle neurons is not well understood, they are thought to be involved in cognitive processes and are affected by Alzheimer's disease and other debilitating brain disorders such as autism and schizophrenia. Spindle neurons were also found in the same location in toothed whales with the largest brains, which suggests that they may be related to brain size.

The authors note that spindle neurons probably first appeared in the common ancestor of hominids about 15 million years ago, since they are observed in great apes and humans, but not in lesser apes and other primates; in cetaceans they evolved earlier, possibly as early as 30 million years ago. It is possible that they were present in the ancestors of all cetaceans, but were retained only in those with the largest brains during their evolution. It may also be that they evolved several times independently in the two cetacean suborders; part of this process may have taken place at the same time as they appeared in the ancestor of great apes, which would be a rare case of parallel evolution.

"In spite of the relative scarcity of information on many cetacean species, it is important to note in this context that sperm whales, killer whales, and certainly humpback whales, exhibit complex social patterns that included intricate communication skills, coalition-formation, cooperation, cultural transmission and tool usage," the authors state. "It is thus likely that some of these abilities are related to comparable histologic complexity in brain organization in cetaceans and in hominids."

The authors conclude: "Cetacean and primate brains may be considered as evolutionary alternatives in neurobiological complexity and as such, it would be compelling to investigate how many convergent cognitive and behavioral features result from largely dissimilar neocortical organization between the two orders." They also suggest that the current study provides a framework for further investigations into the brain and behavior of cetaceans, which are naturally elusive, poorly documented and often endangered.

>From John Wiley & Sons

Seismologists measure heat flow from Earth's molten core to lower mantle

Seismologists measure heat flow from Earth's molten core to lower mantle

Seismologists measure heat flow from Earth's molten core to lower mantle

 

For the first time, scientists have directly measured the amount of heat flowing from the molten metal of Earth's core into a region at the base of the mantle, a process that helps drive both the movement of tectonic plates at the surface and the geodynamo in the core that generates Earth's magnetic field.

The boundary between the core and the mantle lies half-way to the center of the Earth, at a depth of 1,740 miles (2,900 kilometers). Seismologists are able to probe the structure of this region by studying its effects on seismic waves generated by earthquakes. The new temperature measurements, published in the November 24 issue of the journal Science, were obtained by relating seismic observations to a recently discovered mineral transformation that occurs at the ultrahigh pressures and temperatures prevailing near the core-mantle boundary.

"This is the first time we've had a 'thermometer' that tells us the temperature half-way down to the center of the Earth," said Thorne Lay, professor of Earth and planetary sciences at the University of California, Santa Cruz, and first author of the paper.

"If our interpretation is right, it gives us the temperature at two different depths right above each other, so we get not just the absolute temperature but the rate at which the temperature is changing with depth, as well as laterally," Lay said. "This temperature gradient tells us the amount of heat flowing out of the core into the base of the mantle in that location."

As heat flows from the outer core into the mantle, it drives important processes in both the mantle and the core. The mantle is a thick layer of silicate rock that surrounds a dense, predominantly iron core. The outer core is molten liquid and surrounds a solid inner core about the size of the moon. The cooling of the liquid outer core results in fluid motions in the molten metal that produce electric currents, which generate the geomagnetic field.

Heating at the base of the mantle, meanwhile, drives upwellings of hot mantle material that may rise to volcanoes at the surface and contribute to the slow shifting of tectonic plates. These plates consist of the thin, rocky crust and the rigid top layer of the mantle. They float on the deeper mantle, which is solid but plastic enough to flow very slowly, and their movements trigger earthquakes and gradually change the positions of continents.

"Heat flow is the holy grail, because it tells us how much energy powers the geodynamo, and it tells us how much the mantle is being heated from below. The approach we used is the most direct method so far for getting that information," Lay said.

Lay's coauthors include John Hernlund of the Institut de Physique du Globe in Paris, Edward Garnero of Arizona State University, and Michael Thorne of the University of Alaska, Fairbanks. They applied innovative methods for analyzing seismic signals and used a supercomputer to process a large amount of high-quality seismic data, more than ever before analyzed for a localized region in the Earth. The analysis required 72,000 hours of computer time at the Arctic Region Supercomputing Center and produced very detailed seismic velocity models for the deep mantle under the central Pacific.

Their investigation also relied heavily on laboratory studies of mineral physics. Under the extreme pressures and temperatures deep in the Earth, minerals are squeezed into crystal structures not seen on the surface, except in a few specialized mineral physics labs. If scientists take the common mineral olivine and squeeze it--subjecting it to the ultrahigh pressures and temperatures associated with increasing depth in the Earth--the mineral goes through phase transitions involving sudden reorganizations of its crystal structure.

These phase transitions change the mineral's seismic properties--how fast it transmits certain seismic waves--enabling seismologists to detect where the phase transitions occur deep in the Earth. The depth of the transition tells researchers the pressure, and from that they can get the temperature based on laboratory calibrations, since the pressure at which the transition occurs depends on the temperature.

"If we detect a sudden change in the seismic properties of the mantle, we can associate that with a phase transition in the minerals, and we can use the laboratory calibrations to tell us how hot it is. But until two years ago, we never had that kind of information for the lower mantle," Lay said.

In 2004, Japanese researchers working in the laboratory discovered a new form of high-pressure mineral, called postperovskite, that is likely to occur in the lower mantle. Lay and his coauthors detected the phase transition to postperovskite from its precursor perovskite in the lowermost mantle near the core-mantle boundary. Moreover, they observed that the mineral appears and then disappears with increasing depth, forming a layer or "lens" of postperovskite.

"The reason it transforms back into perovskite is that the temperature increases very rapidly right above the core--so rapidly that this high-pressure form becomes unstable," Lay said. "We also see that this layer becomes thinner as you move laterally and eventually thins out and disappears, which you would expect if you have a lateral increase in temperature."

The researchers suspect that upwelling of hot mantle material may be taking place at the edges of the lens of postperovskite. They detected the lens in the lowermost mantle southeast of Hawaii, an area where previous studies have suggested there is an upwelling hot mantle plume from near the core-mantle boundary that may be responsible for the Hawaiian Islands chain of volcanoes.

The temperature at the upper boundary of the lens, where the phase transition from perovskite to postperovskite occurs, is around 2,500 kelvins (4,000 degrees Fahrenheit). At the lower boundary, where the reverse transition occurs, the temperature is around 3,500 kelvins (5,800 degrees Fahrenheit). These two points gave the researchers a temperature gradient from which they calculated the heat flow, or thermal flux: about 80 milliwatts per square meter. Extrapolating to the entire surface of the core gave a total heat flow of about 13 trillion watts.

"We think we are in a relatively hot region of the mantle, and cooler areas will have an even higher heat flux, so this probably sets a lower bound on the total heat flow across the core-mantle boundary. The numbers you might read in a textbook are about one-third of that," Lay said.

Such a high heat flow supports the idea that the upwelling of hot plumes of mantle material from near the core-mantle boundary makes a significant contribution to mantle convection, the slow turnover of mantle material that moves tectonic plates on the surface. It also suggests that the solid inner core may be relatively young.

"The core must have been pretty hot in the past for this much heat to be still coming out, and the inner core, which is slowly solidifying from the inside out as the core cools, may be only about a billion years old," Lay said.

"These implications are not well constrained, but it's amazing that you can go from detecting seismic reflections to this long-term perspective on how the whole system seems to work," he added. "It's a remarkable convergence of advances in seismology, mineral physics, and thermodynamical models of deep mantle processes."

This research was supported by the EarthScope and Geophysics Programs of the National Science Foundation (NSF). The high-quality seismic data analyzed in this study was obtained, in part, by the deployment of hundreds of new seismic stations in the western United States as part of NSF's EarthScope Program.

>From UC Santa Cruz

Horrible sea devil could bite a shark in two

Horrible sea devil could bite a shark in two | Science Blog

 

It could bite a shark in two. It might have been the first "king of the beasts." And it could teach scientists a lot about humans, because it is in the sister group of all jawed vertebrates.

Dunkleosteus terrelli lived 400 million years ago, grew up to 33 feet long and weighed up to four tons. Scientist have known for years that it was a dominant predator, but new embargoed research to be published in the Royal Society journal Biology Letters on November 29 reveals that the force of this predator's bite was remarkably powerful: 1,100pounds. The bladed dentition focused the bite force into a small area, the fang tip, at an incredible force of 8,000pounds per square inch.

Even more surprising is the fact that this fish could also open its mouth very quickly—in just one fiftieth of a second—which created a strong suction force, pulling fast prey into its mouth. Usually a fish has either a powerful bite or a fast bite, but not both.

"The most interesting part of this work for me was discovering that this heavily armored fish was both fast during jaw opening and quite powerful during jaw closing," said Mark Westneat, Curator of Fishes at The Field Museum and co-author of the paper. "This is possible due to the unique engineering design of its skull and different muscles used for opening and closing. And it made this fish into one of the first true apex predators seen in the vertebrate fossil record." This formidable fish was a placoderms, a diverse group of armored fishes that dominated aquatic ecosystems during the Devonian, from 415 million to 360 million years ago. Dunkleosteus' bladed jaws suggest that it was among the first vertebrates to use rapid mouth opening and a powerful bite to capture and fragment evasive prey prior to ingestion.

To determine the bite force, scientists used the fossilized skull of a Dunkleosteus terrelli to recreate the musculature of the ancient fish. This biomechanical model showed the jaw's force and motion, and revealed a highly kinetic skull driven by a unique mechanism based on four rotational joints working in harmony. The extinct fish had the strongest bite of any fish ever, and one of the strongest bites of any animal, rivaling the bites of large alligators and Tyrannosaurus rex.

Thus Dunkleosteus was able to feast on armored aquatic animals that also lived during the Devonian, including sharks, arthropods, ammonoids, and others protected by cuticle, calcium carbonate, or dermal bone.

"Dunkleosteus was able to devour anything in its environment," said Philip Anderson, at the Department of Geophysical Sciences at the University of Chicago and lead author of the research. The bladed jaws, capable of ripping apart prey larger than its own mouth, is a feature sharks didn't develop until 100 million years later.

"Overall, this study shows how useful mechanical engineering theory can be in studying the behavior of fossil animals," he added. "We cannot actually watch these animals feed or interact, but we can understand the range of possible behaviors by examining how the preserved parts are shaped and connected to each other."

>From Field Museum

Mighty predator that ruled the ocean with the most powerful bite

Mighty predator that ruled the ocean with the most powerful bite

 

Scientists now have a wealth of information about jawed vertebrates thanks to discovering the Dunkleosteus terrelli.

Its existence can be traced back to 400 million years ago when it easily lorded over the ocean kingdom. With a formidable length of 33 feet, awesome weight of 4 tons and deadly bladed jaws, it easily ate its way up and through the food chain.

Its bite force is reckoned to equal 11000 pounds that was concentrated into a select area with a super powered force of 80000 pounds per square inch.

The fish is classified as a placoderms that included a wide variety of fishes that were armored and that reigned supreme over the population of aquatic ecosystems. This species dates back to the period of the Devonian that goes as far back as 415 to 360 million years ago.

While scientists have been familiar with the existence of this high powered predator, a fresh lot of important information will soon be available in the Royal Society journal Biology Letters on November 29.

The picture one forms in the mind of this creature defies description: extremely rapid opening of the mouth that generated a powerful suction, effortlessly sucking in prey into its mouth. An awe-inspiring and unique combination of a powerful and fast bite that is not easily found among creatures.

A co-author of the soon to be published paper, Mark Westneat, Curator of Fishes at The Field Museum reveals that he found this feature of a fast and powerful bite particularly interesting. This has been enabled, he says, because of the superb and innovative engineering layout of the skull and mouth muscles. The presence of this trait recognizes the fish as a primary authentic "apex predators seen in the vertebrate fossil record."

A particularly recognizable feature of this fish is its bladed jaws. One of the first vertebrates to be invested with this feature, it allowed for an enormously powerful bite alongwith ruthlessly rapid fragmentation of the prey before being sucked into the mouth.

Such an indepth understanding of the fish by scientists was made possible with their efforts to work on the fossilized skull of a Dunkleosteus terrelli. The scientists then took backward steps to understand how the muscles came to be.

Scientists were able to fashion a biomechanical model that displayed the force and motion of the fish's jaw, the superbly kinetic skull backed by a advanced mechanism of four rotational joints that complemented each other functionally. Scientists are able to state confidently that this creature surpasses the most powerful bites of any fish and any animal including the demonic Tyrannosaurus Rex.

This powerful creature was able to choose its prey among the vast range of aquatic animals that included the formidable shark. Other creatures included arthropods and ammonoids.

This is attested to by Philip Anderson, at the Department of Geophysical Sciences at the University of Chicago who led the research. He observes that this formidable creature could attack and assume just about any inhabitant of the environment. Its features, particularly the bladed jaws were way ahead of its time particularly since we know that it was then seen in sharks after 100 million years.

The study apart from evoking our interest in a truly magnificent fish species has highlighted the relevance of mechanical engineering theory. While we can never have the privilege of actually watching this animal, Anderson says, technology allows us to go back in time and obtain useful impressions of how these creatures lived and their significant body features.

Mass Extinction 250 Million Years Ago Sparked Dramatic Shift To Complex Marine Ecosystems

ScienceDaily: Mass Extinction 250 Million Years Ago Sparked Dramatic Shift To Complex Marine Ecosystems

Mass Extinction 250 Million Years Ago Sparked Dramatic Shift To Complex Marine Ecosystems

The earth experienced its biggest mass extinction about 250 million years ago, an event that wiped out an estimated 95% of marine species and 70% of land species. New research shows that this mass extinction did more than eliminate species: it fundamentally changed the basic ecology of the world's oceans.

In the Cretaceous about 80 million years ago -- well after the end-Permian mass extinction -- the ocean floor was dominated by complex ecosystems that had largely displaced the simple ecosystems. This photograph of a Field Museum diorama of the ocean floor during the Cretaceous shows many free-swimming, complex organisms, including the large ammonoid (in the center of the image) and the long nautiloids (with handlike ends). In addition, the ocean floor is littered with mobile clams and snails. (Photograph of Field Museum diorama by Ron Testa, courtesy of The Field Museum)

Ecologically simple marine communities were largely displaced by complex communities. Furthermore, this apparently abrupt shift set a new pattern that has continued ever since. It reflects the current dominance of higher-metabolism, mobile organisms (such as snails, clams and crabs) that actually go out and find their own food and the decreased diversity of older groups of low-metabolism, stationary organisms (such as lamp shells and sea lilies) that filter nutrients from the water.

So says research published in Science on November 24, 2006. An accompanying article suggests that this striking change escaped detection until now because previous research relied on single numbers--such as the number of species alive at one particular time or the distribution of species in a local community--to track the diversity of marine life. In the new research, however, scientists examined the relative abundance of marine life forms in communities over the past 540 million years.

One reason they were able to do this is because they tapped the new Paleobiology Database ( http://www.pbdb.org), a huge repository of fossil occurrence data. The result is the first broad objective measurement of changes in the complexity of marine ecology over the Phanerozoic.

"We were able to combine a huge data set with new quantitative analyses," says Peter J. Wagner, Associate Curator of Fossil Invertebrates at The Field Museum and lead author of the study. "We think these are the first analyses of this type at this large scale. They show that the end-Permian mass extinction permanently altered not just taxonomic diversity but also the prevailing marine ecosystem structure."

Specifically, the data and analyses concern models of relative abundance found in fossil communities throughout the Phanerozoic. The ecological implications are striking. Simple marine ecosystems suggest that bottom-dwelling organisms partitioned their resources similarly. Complex marine ecosystems suggest that interactions among different species, as well as a greater variety of ways of life, affected abundance distributions. Prior to the end-Permian mass extinction, both types of marine ecosystems (complex and simple) were equally common. After the mass extinction, however, the complex communities outnumbered the simple communities nearly 3:1.

The other authors are Scott Lidgard, Associate Curator of Fossil Invertebrates at The Field Museum, and Matthew A. Kosnik, from the School of Marine and Tropical Biology at the James Cook University in Townsville, Queensland, Australia.

"Tracing how marine communities became more complex over hundreds of millions of years is important because it shows us that there was not an inexorable trend towards modern ecosystems," Wagner said. "If not for this one enormous extinction event at the end of the Permian, then marine ecosystems today might still be like they were 250 million years ago."

These results also might provide a wake-up call, Wagner added: "Studies by modern marine ecologists suggest that humans are reducing certain marine ecosystems to something reminiscent of 550 million years ago, prior to the explosion of animal diversity. The asteroid that wiped out the dinosaurs couldn't manage that."

Lidgard added, "When Pete walked into my office with his preliminary results, I simply couldn't believe them. Paleontologists had long recognized that ecosystems had become more complex, from the origin of single-celled bacteria to the present day. But we had little idea of just how profoundly this one mass extinction--but not the others like it--changed the marine world."