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大家好，胖胖翔来啦！献上今天的科技文，气候类的文章比较多一点，第四和第五的速度是一篇文章，enjoy~
Part I：Speed
【Time 1】
Article 1 Glacier melt causes large fraction of sea level rise Thawing ice contributes nearly as much water to oceans as massive sheets at poles do
Melting glaciers around the world, discrete from the polar ice sheets, accounted for 29 percent of sea level rise from 2003 to 2009, scientists report in the May 17 Science. That’s almost as much sea level rise as the ice sheets themselves contributed during that time.
Glaciers, including those in Greenland and Antarctica that aren’t part of the ice sheets, lost 259 billion tons of ice per year, raising sea level 0.71 millimeters annually. Alex Gardner of Clark University in Worcester, Mass., and colleagues calculated the ice losses using satellite data and ground measurements of glaciers. Most of the melting occurred in Alaska, the Canadian Arctic, Greenland, the southern Andes and the Himalayas and other high mountains of Asia.
The team estimates that, together, the glacier and ice sheet losses explain 60 percent of sea level rise from 2003 to 2009. Other sources include expansion of the ocean as its waters warm.
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Resource: http://www.sciencenews.org/view/generic/id/350478/description/News_in_Brief_Glacier_melt_causes_large_fraction_of_sea_level_rise
【Time 2】
Article 2
Sponges boom thanks to Antarctic ice shelf bust Previously thought to grow at a slow pace, the sea creatures exploded in number
When a catastrophic ice shelf collapse in Antarctica opened up prime ocean real estate, enterprising delicate creatures called glass sponges showed up with unprecedented speed to stake their claim. The finding suggests that even in frigid places, sea life may adapt rapidly to climate change.
Cloaked in darkness and cut off from the photosynthetic power of the sun, the waters beneath Antarctic ice shelves host sparse signs of life. But when a giant shelf collapses — as Larsen A and B did in 1995 and 2002 — solar-powered plankton production ramps up, and scientists think it could jump-start a complex food web of diverse marine life.
A 2007 expedition revealed that sea squirts had taken over the area of the seafloor once shaded by Larsen A. When Claudio Richter, of the Alfred Wegener Institute in Bremerhaven, Germany, and his team went to the same spot in 2011 to see how the squirt coup had progressed, they were shocked at what they found instead.
“The sea squirts were gone, and all of a sudden the glass sponges had tripled,” Richter says.
The discovery, published July 11 in Current Biology, surprised Richter because scientists had previously seen the vase-shaped sponges known as hexactinellids growing at a slow pace, sometimes taking decades to mature. The signals that triggered the sponge boom remain enigmatic.
“This sudden expansion of a glass sponge is unprecedented,” says Paul Dayton of Scripps Institution of Oceanography in La Jolla, Calif. Dayton, who has studied the sponges for decades, sees the boom as a temporary pulse. Other predators will likely take over, he predicts.
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Resource: http://www.sciencenews.org/view/generic/id/351583/description/Sponges_boom_thanks_to_Antarctic_ice_shelf_bust
【Time 3】
Article 3 The solar system has a tail Clover-shaped clumps of charged particles extend billions of kilometers
The solar system drags along a lengthy, twisted tail as it moves through the galaxy, researchers announced July 10 in a press conference and in the Astrophysical Journal.
Scientists had always presumed that a tail existed, said Eric Christian, an astronomer at NASA Goddard Space Flight Center in Greenbelt, Md. “But this is the first time we have data that tells us about the tail.”
The discovery comes from data gathered by the Interstellar Boundary Explorer, or IBEX, a satellite launched in 2008. It charts the trajectories of speedy atoms that originate in the outskirts of the solar system before getting an inward kick from collisions with charged particles from the sun. The distribution of those atoms helps scientists map the boundaries of the heliosphere, the bubble that contains the planets and other material in the solar system and is inflated by particles continually jetting out from the sun.
A cross section of the tail resembles a four-leaf clover, with two clumps of slow-moving solar particles and two of high-speed particles. The data also reveal that the clover shape is flattened and twisted by galactic magnetic fields acting on the sun as it whizzes through the Milky Way at around 84,000 kilometers per hour – the same magnetic fields that cause ribbons of charged particles to wrap around the edge of the heliosphere (SN 11/21/09, p. 15).
The IBEX team could not determine the exact length of the tail, said principal investigator David McComas of Southwest Research Institute in San Antonio, but estimated it at 150 billion kilometers, or 1,000 times the distance between Earth and the sun. The team plans to see whether the tail’s shape changes as the sun’s activity wanes.
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Resource:
http://www.sciencenews.org/view/generic/id/351477/description/News_in_Brief_The_solar_system_has_a_tail
【Time 4】 Article 4
Tyrannosaurus rex hunted for live prey Tooth found in victim's tail shows carnivorous dinosaur did not just feed on carcasses.
Audiences the world over gripped their seats as the Tyrannosaurus rex in Jurassic Park sank its teeth into velociraptors and chewed up avaricious lawyers. In spite of this portrayal, there was no hard evidence at the time that the dinosaur actually bit into anything living, and some palaeontologists have proposed that it scavenged for its meals. But now, a team has found definitive evidence that the T. rex did hunt for live prey.
The researchers found a T. rex tooth stuck between vertebrae in the tail of a herbivorous duck-billed hadrosaur. The specimen was excavated from the Hell Creek Formation, a famous fossil locality in South Dakota.
Scrapes, bites and even dislodged T. rex teeth stuck in the bones of other dinosaur species are common, but there has previously been no way to know whether these bites were made while the prey was being actively attacked by a T. rex, or whether the animal had died in some other way and then been scavenged on by the toothy dinosaur.
The latest find is different because the T. rex tooth is surrounded by bone that clearly grew after the tooth became lodged there. The only way that such a situation could arise is if a T. rex had bitten the hadrosaur, lost its tooth in the hadrosaur’s tail and then also lost its prey. In the weeks that followed the predation, the tail of the lucky hadrosaur healed up and bone regenerated around the predator’s lodged tooth, the authors report in Proceedings of the National Academy of Sciences.
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【Time 5】
The team argues that because the tooth is embedded in the tail bones (see picture), the wound was likely made while T. rex was chasing after its prey. “It’s a smoking gun. We finally have Tyrannosaurus rex caught in the act,” says Bruce Rothschild, a palaeopathologist at the University of Kansas in Lawrence and a co-author of the paper.
“We’ve seen plenty of re-healed bite marks attributed to Tyrannosaurus rex, but it’s hard to confirm identity with those,” says Thomas Holtz, a vertebrate palaeontologist from the University of Maryland in College Park. “Actually having the broken tooth makes it easy to determine who was doing the hunting here,”
Bone of contention As intriguing as the fossil is, some think that it does not change much. “I’ve long argued that Tyrannosaurus rex was an opportunist like a hyena, sometimes hunting and sometimes scavenging. This provides no evidence to the contrary,” says Jack Horner, a palaeontologist at the Museum of the Rockies in Bozeman, Montana, who served as scientific adviser on the Jurassic Park films.
In fact, many palaeontologists are getting fed up with what they consider to be a phony debate over predation and scavenging. “Great galloping lizards!” exclaims John Hutchinson, an evolutionary physiologist at the Royal Veterinary College in London. “It is so frustrating to see provocative half-baked ideas about celebrity species like Tyrannosaurus rex drawing the public’s attention when there is so much more interesting palaeontology to be talking about.”
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Resource: http://www.nature.com/news/tyrannosaurus-rex-hunted-for-live-prey-1.13381
Part II： Obstacle
【Time 6】
Natural defences can sharply limit coastal damage Reefs, dunes and marshes are key to protecting lives and property against storm surges and long-term sea-level rise.
Coastal forests, coral reefs, sand dunes and wetlands are just a few of the natural habitats that protect two-thirds of of the US coastline from hazards such as hurricane storm surges — shielding not only high-value properties in New York and California but also the poor in Texas and the elderly in Florida.
By the end of the century, 2.1 million people and US$400 billion to US$500 billion of residential property will be exposed to the highest hazard risk. But if protective habitats are lost, the number of people and total property value at risk could double, according to work published today in Nature Climate Change.
“Where we’ve got these ecosystems intact, we need to keep it that way. Otherwise, massive investments will be required to protect people and property,” says author Katie Arkema, a marine ecologist in Seattle, Washington with the Natural Capital Project, headquartered in Stanford, California. The work presents the first map of the US coastline that identifies where and how much protection comes from different habitats.
“This is ground-breaking work to show the extent to which habitats may protect property and people along the coastlines of the entire United States under different climate-change scenarios — no one’s done that before,” says Edward Barbier, a natural-resource economist at the University of Wyoming in Laramie, who published a study in March demonstrating that the presence of marshes in Louisiana could reduce storm property damage.
This study comes at a time when coastal-defence planning is under way in areas, such as New York city and Louisiana, that were hit hard by recent hurricanes. Increasingly, plans are moving beyond solely engineered solutions, such as levees or seawalls, to include conservation-based protection measures such as wetland restoration and dune creation.
Study co-athor Peter Kareiva, chief scientist at the Nature Conservancy, a conservation organization based in Arlington, Virginia, says that the models used in their work could help further a global movement to take stock of the coastal protections afforded by natural habitats. “It really is going to get to the point where we’ll be able to put dollar values on what we gain from restoring natural habitats,” he says.
Ranking habitats Arkema and her colleagues took the ambitious step of synthesizing a hazard model for the US coast, that took into account ecosystem data, projected climate scenarios, socio-economic data and property values to identify where habitats offered the greatest coastal protection. They identified nine habitats — including coral and oyster reefs, wetlands, dunes, seagrass beds and kelp forests — and ranked the level of protection each gave. They then scored each 1-kilometre strip of coastline to tally the total protection by habitat in an area.
The team also created a hazard index based on physical and biological variables that influence exposure to sea-level rises or to storm surges. “We have to look at the shoreline elevation, wave exposure, and whether it’s rocky or muddy to determine where habitats become important for protection,” says Arkema. The researchers identified areas with the highest exposure to flooding and erosion under five current and future climate scenarios—with and without habitat. The final step, overlaying the social variables on top of the hazard index, indicated that coastal habitats in Florida, New York and California defend the most people as well as the greatest amount in property values from storm surges.
Rob Thieler, a coastal geologist at the US Geological Survey in Woods Hole, Massachusetts, says that this model is a good first step in demonstrating the potential value of coastal habitats, but that it will undoubtedly require further refinements and more robust regional assessments. It can’t, however, identify where a restored wetland would be most viable. “One key thing missing, as mentioned in the paper, is that we just don’t have a good scientific understanding of how well coastal habitats will persist in the future,” he says.
The authors agree. According to Kareiva, two things are needed to turn this science into something that changes the way the world works: good-quality data on habitats and a rigorous way to cost-compare engineered and natural protections.
In the meantime, Nature Conservancy scientists are already using the models underlying this study to rebuild oyster reefs off the coast of Alabama—a project that has trapped sediment and dissipated wave energy that normally would have eroded the shore. “Until we started putting in these oyster reefs, I don’t think any of us fully appreciated the extent to which they would increase the shoreline,” Kareiva says.
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Resource: http://www.nature.com/news/natural-defences-can-sharply-limit-coastal-damage-1.13380 | 
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发表于 2013-7-16 23:21:32
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