Monday, June 25, 2012
Wednesday, June 20, 2012
Tuesday, June 19, 2012
Ancient Antarctica was warmer and wetter than previously suspected, enough to support vegetation along its edges, according to a new study.
By examining the remnants of plant leaf wax found in sediment cores taken below the Ross Ice Shelf, scientists from the University of Southern California, Louisiana State University and NASA's Jet Propulsion Laboratory were able to determine that summer temperatures along the Antarctic coast 15 to 20 million years ago were 20 degrees Fahrenheit (11 degrees Celsius) warmer than they are today, reaching up to about 45 degrees Fahrenheit (7 degrees Celsius); with several times more precipitation.
This occurred during a period of global warming in the middle Miocene epoch that coincided with increased levels of atmospheric carbon dioxide.
"This is some of the first evidence of just how much warmer it was," said Sarah J. Feakins, an assistant professor of earth sciences at the USC Dornsife College of Letters, Arts and Sciences and lead author of a paper on the research published in Nature Geoscience on June 17.
Scientists began to suspect that high-latitude temperatures during the middle Miocene were warmer than previously believed when Sophie Warny, co-author of the Nature Geoscience paper, discovered large quantities of pollen and algae in sediment cores taken around Antarctica.
Fossils of plant life in Antarctica are difficult to come by because the movement of the massive ice sheets covering the landmass grinds and scrapes away the evidence.
"Deep sea cores are ideal to look for clues of past vegetation as the fossils deposited are protected from ice-sheet advances, but these are technically very difficult to acquire in the Antarctic and require international collaboration," said Warny, assistant professor of palynology at Louisiana State University.
"Ice cores can only go back about one million years," Feakins said. "Sediment cores allow us to go into 'deep time.'"
Tipped off by the tiny pollen samples, the USC-led team opted to look at the remnants of leaf wax taken from sediment cores for clues. Leaf wax acts as a record of climate change by documenting details about the hydrogen isotope ratios of the water the plant drank while it was alive.
Jung-Eun Lee, a scientist at NASA's Jet Propulsion Laboratory and a co-author on the paper, created model experiments to find out just how much warmer and wetter climate may have been. "When the planet heats up, the biggest changes are seen toward the poles. The southward movement of rain bands made the margins of Antarctica less like a polar desert, and more like present-day Iceland."
The peak of Antarctic greening during this time period, known as the middle Miocene, occurred between 16.4 and 15.7 million years ago. For reference, this was well after the age of the dinosaurs, which died out 64 million years ago. During the Miocene epoch, mostly modern looking animals such as three-toed horses, deer and camel roamed Earth. Various species of apes also existed, though modern humans did not appear until 200,000 years ago.
Monday, June 18, 2012
New clues in a mass murder that took place 252 million years ago points to a suspect: Ocean acidification may have driven the largest extinction of animals the world has ever seen.
Carbon dioxide belched out by volcanic eruptions during the Permian period could have caused the oceans’ chemistry to change. That’s worrisome because CO2 levels are rising today — thanks to the burning of fossil fuels — and pushing down seawater pH, researchers report online June 8 in Geology.
“The worst biodiversity catastrophe we've had in the history of animal life appears to have been associated with ocean acidification and other kinds of environmental changes we anticipate in the coming centuries,” says Jonathan Payne, a paleobiologist at Stanford University. “It’s a useful comparison point to have in mind as we think about the future of the modern oceans.”
The Great Dying at the end of the Permian period 252 million years ago wiped out most animal species, with marine critters hit hardest. Popular explanations include an upwelling of deep, oxygen-poor waters that suffocated life near the surface, or perhaps huge eruptions in Siberia that warmed and acidified oceans.
To distinguish between those scenarios, Payne and colleagues examined minerals in marine sediments and in fossilized, toothlike parts from prehistoric creatures that looked like eels. The minerals, made from calcium that had once been dissolved in seawater, had higher proportions of a lighter form of the element after about 250 million years ago, the researchers found.
A world warmed by volcanic eruptions would have increased levels of this light calcium isotope, the researchers’ simulations suggest. More intense rains would have flushed calcium into the ocean by eroding rocks on land, which tend to be made of the light calcium. Seawater that soaked up carbon dioxide and became more acidic would have stunted the productivity of organisms that pull calcium out of the water, allowing it to build up in the ocean.
Other lines of evidence corroborate this story. Previous studies have found that not only calcium but also carbon tends to get lighter in limestone that was formed after the extinction, a shift that could also be explained by more erosion on land. And acidified oceans would have made life particularly difficult for thick-shelled creatures, which died out in droves during the extinction.
But Paul Wignall, a paleontologist at the University of Leeds in England, says the records are too crude to reveal the timing of the calcium shift. The light calcium could have come from the shells of creatures wiped out by other means.
“I suspect what their data really record is that a lot of skeletal invertebrates died out,” says Wignall. “They've recorded an effect, not the cause.”
I need to update the Great Dying post.
Friday, June 15, 2012
Between 50,000 and 45,000 years ago, in the Late Quaternary, Australia suffered a major loss of its megafauna. Sixty taxa of mammals, predominantly large leaf- and twig-eating animals called browsers, went extinct, including all 19 species exceeding 100 kilograms, like the half-ton Palorchestes azael, a marsupial similar to a ground sloth, and the rhinoceros-sized Diprotodon. Also lost were more than half of species weighing between 10 and 100 kilograms, such as the giant koala, Phascolarctos stirtoni, as well as three large reptiles and a flightless bird, Genyornis newtoni.
Recent studies indicate that humans colonized the continent during that interval. Given this coincident timing and the lack of evidence for dramatic climate change during that period, a human cause for the extinction has long been inferred, but the extinction mechanism has never been resolved. Now Gifford Miller, a geologist at the University of Colorado at Boulder, and his colleagues think they have uncovered a potential mechanism for the megafauna’s disappearance: a change in the ecosystem that made consistent food options no longer available.
The selective loss of large browsers suggested by Miller and his colleagues, including John Magee of the Australian National University in Canberra and Marilyn Fogel of the Carnegie Institution of Washington Geophysical Laboratory in Washington, D.C., indicates that an ecosystem change played an important role in the extinction. To test this hypothesis, Miller searched for proxies. Neither pollen, the most commonly used indicator for ecosystem changes, nor bones are typically preserved in Australia’s arid interior. So, for nearly two decades, Miller has roamed the Outback, collecting fossil bird eggshells — the most common megafaunal remains in Australia’s arid and semi-arid regions — and marsupial teeth. By analyzing the biominerals in these finds, the researchers have pieced together the ancient diets of three Australian animals: the extinct flightless bird Genyornis, along with the extant emu (another giant flightless bird) and the wombat (a small marsupial). They used these data to reconstruct the complex interactions between humans, vegetation, climate and megafauna in Australia over the last 140,000 years.
To reconstruct the creatures’ diets, Miller and his colleagues first dated the remains by measuring the extent of amino acid racemization — the inversion of an amino acid from its protein configuration to its nonprotein mirror image, a process that proceeds slowly within the calcite crystals of the eggshell after it is laid — and converting these results to calendar ages using radiocarbon, uranium/thorium, and luminescence dating. They also analyzed the samples’ carbon isotope composition, which is transferred from food to teeth, eggshells and bones, leaving behind a record of the animals’ diet.
This 140,000-year record of dietary carbon, collected from three broadly separated regions, provides clear evidence for an abrupt ecological shift — and a permanent reduction in available food sources — about the time of human colonization, Miller says. Prior to 50,000 years ago, the emu eggshell carbon isotope values varied widely, exhibiting a pattern consistent with an opportunistic feeder living in an environment where moisture varied considerably, with some years wet enough for nutritious grasslands to grow abundantly and other, drier years dominated by shrubs and trees. From 50,000 to 45,000 years ago, the mean carbon isotope ratios in both emu shells and wombat teeth decreased, and it has remained low ever since. This isotopic shift documents an increased reliance by emus and wombats on shrubby plants and trees, he says. Being opportunistic eaters, emus adapted their diet to a large-scale change in vegetation that occurred around that time.
In contrast, dietary carbon data from Genyornis eggshells from 140,000 to 50,000 years ago indicate a more specialized feeding strategy for this heavier bird. The carbon isotopes indicate that Genyornis always included some grass sources, unlike the emu, which prefer grass but can tolerate a diet based entirely on shrubs and trees. Miller and his colleagues concluded in two studies, published in Science and Climate of the Past, that Genyornis consumed a more restricted diet that was no longer available after 50,000 years ago.
The team’s findings of a dramatic upheaval at the base of the food chain are consistent with the hypothesis that systematic burning of the landscape by humans permanently converted the previous ecosystem from nutritious tree and shrub savanna (with frequent years of rich grasslands) to the modern desert scrub environment. Animals that could adapt survived; those that could not went extinct.
I need to write the 6th mass extinction post.
Thursday, June 14, 2012
Speaking of BART....about 2:15 AM in West Oakland at a retiree home that was under construction. Its looking like arson. If they find the culprit, they are going to need to put that person in a very, very safe place. The whole Bay might come for him.
Tuesday, June 12, 2012
Tuesday, June 05, 2012
From the NY Times via BioCreativity.
I have not seen the original article, but I suspect they are excluding the megafauna that was wiped between 25k to 10k years ago. From the paleo POV - and the likely cause *cough*us*cough* - this is the same mass extinction that's on a roll. 25k years is hard to distinguish in the geological record. 10k is about as fine grained as you get. Esp when compared to the other mass extinctions.
I've not been blogging in some time. No small part of that has been due to the GLXP activities. That is continuing and will actually intensify. However, for my mental sanity, I still need an outlet for my thoughts and to, honestly, just write. I have ben frustrated in that I have not been able to do that in quite a while and part of me, that part that craves to put characters to screen, has been feeling stuffed up, like a sinus infection. No more.
I am back.
More than news posts on their way.
Monday, June 04, 2012
NASA will be getting two unused space surveillance satellites from the US’s National Reconnaissance Office, which could possibly be used to search for dark energy. In articles in the Washington Post and the New York Times, NASA and NRO officials revealed the two unused and not-fully-built satellites are available for NASA to use as they see fit. While the satellites don’t have astronomical instruments and are still in a warehouse, they do have 2.4-meter (7.9 feet) mirrors, just like Hubble, with a wider field of view and a maneuverable secondary mirror that makes it possible to obtain better-focused images.
“This is a total game changer,” said David N. Spergel of Princeton, quoted in the New York Times, who is co-chairman of a committee on astronomy and astrophysics for the National Academy of Sciences.
Reportedly, the NRO contacted NASA in 2011 about the two spy satellites. Since taking over as head of the NASA Science Directorate early this year, former Hubble repairman John Grunsfeld has been working with scientists and other NASA officials to quietly study the possibility of using the two satellites as “repurposed telescopes.”
Originally designed to look at Earth for surveillance, the two telescopes could be turned to look at the heavens instead, as the National Reconnaissance Office said they no longer needed them for spy missions. Why two such spy telescopes were under construction and then scrapped is not clear.
Described as not fully built and some parts being in “bits and pieces,” NASA will have to decide on how they should be used, build additional instruments, launch them, and support the operations.
Reportedly, Grunsfeld and his secret team have come up with a plan to turn one of the telescopes to investigate the mysterious dark energy that is speeding up the expansion of the universe.
These are very similar to the Hubble. Really, really similar. They lack instruments and a launch...but even so, these could be just the thing that is needed to save the Astrophysics community from the James Webb monster's appetite for budget $.