Friday, January 27, 2012

What Happened Prior to the Carbon Prior to the Marinoan Glaciations (Snowball Earth)


In a study published in the journal Geology, scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science suggest that the large changes in the carbon isotopic composition of carbonates which occurred prior to the major climatic event more than 500 million years ago, known as 'Snowball Earth,' are unrelated to worldwide glacial events.

"Our study suggests that the geochemical record documented in rocks prior to the Marinoan glaciation or 'Snowball Earth' are unrelated to the glaciation itself," said UM Rosenstiel professor Peter Swart, a co-author of the study. "Instead the changes in the carbon isotopic ratio are related to alteration by freshwater as sea level fell."

In order to better understand the environmental conditions prior to 'Snowball Earth', the research team analyzed geochemical signatures preserved in carbonate rock cores from similar climactic events that happened more recently — two million years ago — during the Pliocene-Pleistocene period.

The team analyzed the ratio of the rare isotope of carbon (13C) to the more abundant carbon isotope (12C) from cores drilled in the Bahamas and the Enewetak Atoll in the Pacific Ocean. The geochemical patterns that were observed in these cores were nearly identical to the pattern seen prior to the Marinoan glaciation, which suggests that the alteration of rocks by water, a process known as diagenesis, is the source of the changes seen during that time period.

Prior to this study, scientists theorized that large changes in the cycling of carbon between the organic and inorganic reservoirs occurred in the atmosphere and oceans, setting the stage for the global glacial event known as 'Snowball Earth'.

"It is widely accepted that changes in the carbon isotopic ratio during the Pliocene-Pleistocene time are the result of alteration of rocks by freshwater," said Swart. "We believe this is also what occurred during the Neoproterozoic. Instead of being related to massive and complicated changes in the carbon cycle, the variations seen in the Neoproterozoic can be explained by simple process which we understand very well."

Scientists acknowledge that multiple sea level fluctuations occurred during the Pliocene-Pleistocene glaciations resulting from water being locked up in glaciers. Similar sea-level changes during the Neoproterozoic caused the variations in the global carbon isotopic signal preserved in the older rocks, not a change in the distribution of carbon as had been widely postulated.


I don't see the paper online as yet...

All These Worlds...



Wednesday, January 18, 2012

Greenhouse Gases Postpone (Cancel?) Next Glacial Cycle

Unprecedented levels of greenhouse gases in the Earth's atmosphere are disrupting normal patterns of glaciation, according to a study co-authored by a University of Florida researcher and published online Jan. 8 in Nature Geoscience.

The Earth's current warm period that began about 11,000 years ago should give way to another ice age within about 1,500 years, according to accepted astronomical models. However, current levels of carbon dioxide are trapping too much heat in the atmosphere to allow the Earth to cool as it has in its prehistoric past in response to changes in Earth's orbital pattern. The research team, a collaboration among University College London, University of Cambridge and UF, said their data indicate that the next ice age will likely be delayed by tens of thousands of years.

That may sound like good news, but it probably isn't, said Jim Channell, distinguished professor of geology at UF and co-author.

"Ice sheets like those in western Antarctica are already destabilized by global warming," said Channell. "When they eventually slough off and become a part of the ocean's volume, it will have a dramatic effect on sea level." Ice sheets will continue to melt until the next phase of cooling begins in earnest.

The study looks at the prehistoric climate-change drivers of the past to project the onset of the next ice age. Using astronomical models that show Earth's orbital pattern with all of its fluctuations and wobbles over the last several million years, astronomers can calculate the amount of solar heat that has reached the Earth's atmosphere during past glacial and interglacial periods.

"We know from past records that Earth's orbital characteristics during our present interglacial period are a dead ringer for orbital characteristics in an interglacial period 780,000 years ago," said Channell. The pattern suggests that our current period of warmth should be ending within about 1,500 years.

However, there is a much higher concentration of greenhouse gases trapping the sun's heat in the Earth's atmosphere now than there was in at least the last several million years, he said. So the cooling that would naturally occur due to changes in the Earth's orbital characteristics are unable to turn the temperature tide.

Over the past million years, the Earth's carbon dioxide levels, as recorded in ice core samples, have never reached more than 280 parts per million in the atmosphere. "We are now at 390 parts per million," Channell said. The sudden spike has occurred in the last 150 years.

For millions of years, carbon dioxide levels have ebbed and flowed between ice ages. Orbital patterns initiate periods of warming that cause ocean circulation to change. The changes cause carbon dioxide-rich water in the deep ocean to well up toward the surface where the carbon dioxide is released as a gas back into the atmosphere. The increase in atmospheric carbon dioxide then drives further warming and eventually the orbital pattern shifts again and decreases the amount of solar heat that reaches the Earth.

"The problem is that now we have added to the total amount of CO2 cycling through the system by burning fossil fuels," said Channell. "The cooling forces can't keep up."


1. Duh.

2. This may well be a permanent off ramp for Ice Age we have been in.

3. There might have been interglacial ending on-ramps we missed before and are missing right now.

4. Keep in mind it took over 50k years for the last time there was a huge build up in CO2 like the modern one took over 50k years for the environment to recover...and it didn't go back to what it was before.

5. The main question is whether or not we are going to have a Neo-Eocene (hot, wet) or Neo-Oligocene (hot dry).

NorAm Mammalian Fauna Diversity Shifts with Climate

(original artist here)
History often seems to happen in waves – fashion and musical tastes turn over every decade and empires give way to new ones over centuries. A similar pattern characterizes the last 65 million years of natural history in North America, where a novel quantitative analysis has identified six distinct, consecutive waves of mammal species diversity, or "evolutionary faunas." What force of history determined the destiny of these groupings? The numbers say it was typically climate change.

"Although we've always known in a general way that mammals respond to climatic change over time, there has been controversy as to whether this can be demonstrated in a quantitative fashion," said Brown University evolutionary biology Professor Christine Janis. "We show that the rise and fall of these faunas is indeed correlated with climatic change – the rise or fall of global paleotemperatures – and also influenced by other more local perturbations such as immigration events."

Specifically, of the six waves of species diversity that Janis and her Spanish collaborators describe online this week in the Proceedings of the National Academy of Sciences, four show statistically significant correlations with major changes in temperature. The two transitions that show a weaker but still apparent correlation with the pattern correspond to periods when mammals from other continents happened to invade in large numbers, said Janis, who is the paper's senior and second author.

Previous studies of the potential connection between climate change and mammal species evolution have counted total species diversity in the fossil record over similar time periods. But in this analysis, led by postdoctoral scholar Borja Figueirido, the scientists asked whether there were any patterns within the species diversity that might be significant. They were guided by a similar methodology pioneered in a study of "evolutionary faunas" in marine invertebrates by Janis' late husband Jack Sepkoski, who was a paleontologist at the University of Chicago.

What the authors found is six distinct and consecutive groupings of mammal species that shared a common rise, peak and decline in their numbers. For example, the "Paleocene fauna" had largely given way to the "early-middle Eocene fauna" by about 50 million years ago. Moreover, the authors found that these transfers of dominance correlated with temperature shifts, as reflected in data on past levels of atmospheric oxygen (determined from the isotopes in the fossilized remains of deep sea microorganisms).

By the numbers, the research showed correlations between species diversity and temperature change, but qualitatively, it also provided a narrative of how the traits of typical species within each wave made sense given the changes in vegetation that followed changes in climate. For example, after a warming episode about 20 million years in the early Miocene epoch, the dominant vegetation transitioned from woodland to a savannah-like grassland. It is no surprise, therefore, that many of the herbivores that comprised the accompanying "Miocene fauna" had high-crowned teeth that allowed them to eat the foods from those savannah sources.


Original paper here.

Wednesday, January 11, 2012

Tasmanian Triassic Dicynodont Found

A Tasmanian couple on a quiet walk down to the beach a few years ago discovered a fossil that scientists say is 250 million years old.

Bob and Penny Tyson found the fossilised remains of a dicynodont, a tusked plant-eating animal that's believed to be a distant ancestor of modern mammals.

Roughly the size of a cow, it had two tusks and a horny beak.

Queensland Museum palaeontologist Andrew Rozefelds says the dicynodont lived on every continent, including Antarctica.

The ABC reports that until now, the only specimen previously found in Australia was in Queensland almost 30 years ago.

He describes the dicynodont as a ''strange-looking beast''.

''They had tusks at the front of their skull, which makes you think maybe they were a carnivore, but in fact they were a plant eater.

''They had slightly splayed legs, so their posture was quite different to say some of the modern mammals you see and they're very, very distantly related to modern mammals.''


I don't see a paper at the JVP. However, considering the journal is a little outdated from the last time they updated what's online, I'm not surprised. Previously, in Tasmania the predominant fossils were temnospondyls. And not much else.

Tuesday, January 10, 2012

Even Nastier Siberian Traps

Around 250 million years ago, at the end of the Permian geologic period, there was a mass extinction so severe that it remains the most traumatic known species die-off in Earth's history. Although the cause of this event is a mystery, it has been speculated that the eruption of a large swath of volcanic rock in Russia called the Siberian Traps was a trigger for the extinction. New research from Carnegie's Linda Elkins-Tanton and her co-authors offers insight into how this volcanism could have contributed to drastic deterioration in the global environment of the period. Their work is published January 9 in Earth and Planetary Science Letters.

The end-Permian mass extinction saw the sudden loss of more than 90 percent of marine species and more than 70 percent of terrestrial species. The fossil record suggests that ecological diversity did not fully recover until several million years after the main pulse of the extinction. This suggests that environmental conditions remained inhospitable for an extended period of time.

Volcanic activity in the Siberian Traps has been proposed as one of the mechanisms that may have triggered the mass extinction. Gases released as a result of Siberian magmatism could have caused environmental damage. For example, perhaps sulfur particles in the atmosphere reflected the sun's heat back into space, cooling the planet; or maybe chlorine and other chemically similar nonmetal elements called halogens significantly damaged the ozone layer in the stratosphere.

The team designed experiments to examine these possibilities.

Led by Benjamin Black of the Massachusetts Institute of Technology, the group included Elkins-Tanton, formerly of MIT and now director of Carnegie's Department of Terrestrial Magnetism, Michael C. Rowe of Washington State University, and Ingrid Ukstins Peate of the University of Iowa.

The geology of the Siberian Traps is comprised of flood basalts, which form when giant lava eruptions coat large swaths of land or ocean floor with basaltic lava. This lava hardens into rock formations. The team investigated concentrations of sulfur, chlorine and fluorine (another halogen) that were dissolved in tiny samples of ancient magma found within basalt samples from the Siberian Traps. These small frozen droplets, which preserve a record of volcanic gases from the time of the eruption 250 million years ago, are called melt inclusions.

Sulfur, chlorine, and fluorine gasses could have been released into the atmosphere from eruptions spewing out of large fissures, which is common in basalt flood formation. Plumes escaping from these cracks could have reached the stratosphere. If sulfur, chlorine, and fluorine made it to the upper atmosphere, these gasses could have cause a wide array of adverse climate events, including temperature change and acid rain.

Based on their findings, the team estimated that between 6,300 and 7,800 gigatonnes of sulfur, between 3,400 and 8,700 gigatonnes of chlorine, and between 7,100 and 13,700 gigatonnes of fluorine were released from magma in the Siberian Traps during the end of the Permian period.


Anyone have the paper itself? I've not been able to find it on the server.

Friday, January 06, 2012

Siberian Traps Were Meaner Than We Knew

Explosive eruption of coal and basalt and the end-Permian mass extinction

1. Darcy E. Ogden (a)
2. Norman H. Sleep (b,*)


a. Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, 1156 Gilman Drive, La Jolla, CA 92093-0225; and

b. Department of Geophysics, Mitchell Building, 397 Panama Mall, Stanford University, Stanford CA 94305

* To whom correspondence should be addressed. E-mail: norm@stanford.edu.

Abstract:

The end-Permian extinction decimated up to 95% of carbonate shell-bearing marine species and 80% of land animals. Isotopic excursions, dissolution of shallow marine carbonates, and the demise of carbonate shell-bearing organisms suggest global warming and ocean acidification. The temporal association of the extinction with the Siberia flood basalts at approximately 250 Ma is well known, and recent evidence suggests these flood basalts may have mobilized carbon in thick deposits of organic-rich sediments. Large isotopic excursions recorded in this period are potentially explained by rapid venting of coal-derived methane, which has primarily been attributed to metamorphism of coal by basaltic intrusion. However, recently discovered contemporaneous deposits of fly ash in northern Canada suggest large-scale combustion of coal as an additional mechanism for rapid release of carbon. This massive coal combustion may have resulted from explosive interaction with basalt sills of the Siberian Traps. Here we present physical analysis of explosive eruption of coal and basalt, demonstrating that it is a viable mechanism for global extinction. We describe and constrain the physics of this process including necessary magnitudes of basaltic intrusion, mixing and mobilization of coal and basalt, ascent to the surface, explosive combustion, and the atmospheric rise necessary for global distribution.


Explosive coal eruptions and mass mercury poisoning. Halogen emitting lakes and ozone layer depletion. Its definitely time for a rewrite of my PT Extinction post.

...in my copious amounts of spare time.

On Titan the Rain Mainly Falls on the Plains in Spring and Fall

Saturn's largest moon, Titan, is an intriguing, alien world that's covered in a thick atmosphere with abundant methane. With an average surface temperature of a brisk -297 degrees Fahrenheit (about 90 kelvins) and a diameter just less than half of Earth's, Titan boasts methane clouds and fog, as well as rainstorms and plentiful lakes of liquid methane. It's the only place in the solar system, other than Earth, that has large bodies of liquid on its surface.

The origins of many of these features, however, remain puzzling to scientists. Now, researchers at the California Institute of Technology (Caltech) have developed a computer model of Titan's atmosphere and methane cycle that, for the first time, explains many of these phenomena in a relatively simple and coherent way.

In particular, the new model explains three baffling observations of Titan. One oddity was discovered in 2009, when researchers led by Caltech professor of planetary science Oded Aharonson found that Titan's methane lakes tend to cluster around its poles—and noted that there are more lakes in the northern hemisphere than in the south.

Secondly, the areas at low latitudes, near Titan's equator, are known to be dry, lacking lakes and regular precipitation. But when the Huygens probe landed on Titan in 2005, it saw channels carved out by flowing liquid—possibly runoff from rain. And in 2009, Caltech researchers discovered raging storms that may have brought rain to this supposedly dry region.

Finally, scientists uncovered a third mystery when they noticed that clouds observed over the past decade—during summer in Titan's southern hemisphere—cluster around southern middle and high latitudes.

Scientists have proposed various ideas to explain these features, but their models either can't account for all of the observations, or do so by requiring exotic processes, such as cryogenic volcanoes that spew methane vapor to form clouds. The Caltech researchers say their new computer model, on the other hand, can explain all these observations—and does so using relatively straightforward and fundamental principles of atmospheric circulation.

"We have a unified explanation for many of the observed features," says Tapio Schneider, the Frank J. Gilloon Professor of Environmental Science and Engineering. "It doesn't require cryovolcanoes or anything esoteric." Schneider, along with Caltech graduate student Sonja Graves, former Caltech graduate student Emily Schaller (PhD '08), and Mike Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy, have published their findings in the January 5 issue of the journal Nature.

Schneider says the team's simulations were able to reproduce the distribution of clouds that's been observed—which was not the case with previous models. The new model also produces the right distribution of lakes. Methane tends to collect in lakes around the poles because the sunlight there is weaker on average, he explains. Energy from the sun normally evaporates liquid methane on the surface, but since there's generally less sunlight at the poles, it's easier for liquid methane there to accumulate into lakes.

But then why are there more lakes in the northern hemisphere? Schneider points out that Saturn's slightly elongated orbit means that Titan is farther from the sun when it's summer in the northern hemisphere. Kepler's second law says that a planet orbits more slowly the farther it is from the sun, which means that Titan spends more time at the far end of its elliptical orbit, when it's summer in the north. As a result, the northern summer is longer than the southern summer. And since summer is the rainy season in Titan's polar regions, the rainy season is longer in the north. Even though the summer rains in the southern hemisphere are more intense—triggered by stronger sunlight, since Titan is closer to the sun during southern summer—there's more rain over the course of a year in the north, filling more lakes.

In general, however, Titan's weather is bland, and the regions near the equator are particularly dull, the researchers say. Years can go by without a drop of rain, leaving the lower latitudes of Titan parched. It was a surprise, then, when the Huygens probe saw evidence of rain runoff in the terrain. That surprise only increased in 2009 when Schaller, Brown, Schneider, and then–postdoctoral scholar Henry Roe discovered storms in this same, supposedly rainless, area.

No one really understood how those storms arose, and previous models failed to generate anything more than a drizzle. But the new model was able to produce intense downpours during Titan's vernal and autumnal equinoxes—enough liquid to carve out the type of channels that Huygens found. With the model, the researchers can now explain the storms. "It rains very rarely at low latitudes," Schneider says. "But when it rains, it pours."

The new model differs from previous ones in that it's three-dimensional and simulates Titan's atmosphere for 135 Titan years—equivalent to 3,000 years on Earth—so that it reaches a steady state. The model also couples the atmosphere to a methane reservoir on the surface, simulating how methane is transported throughout the moon.

The model successfully reproduces what scientists have already seen on Titan, but perhaps what's most exciting, Schneider says, is that it also can predict what scientists will see in the next few years. For instance, based on the simulations, the researchers predict that the changing seasons will cause the lake levels in the north to rise over the next 15 years. They also predict that clouds will form around the north pole in the next two years. Making testable predictions is "a rare and beautiful opportunity in the planetary sciences," Schneider says. "In a few years, we'll know how right or wrong they are.


Its a frozen Tanith!

A Few Xmas Pix




Its been a while since I put up some family pix. Here's my daughter, Avrora, now age 6, and my son, Orest, now 2.

Another PT Extinction Factor: Mercury Poisoning


Scientists have uncovered a lot about the Earth's greatest extinction event that took place 250 million years ago when rapid climate change wiped out nearly all marine species and a majority of those on land. Now, they have discovered a new culprit likely involved in the annihilation: an influx of mercury into the eco-system.

"No one had ever looked to see if mercury was a potential culprit. This was a time of the greatest volcanic activity in Earth's history and we know today that the largest source of mercury comes from volcanic eruptions," says Dr. Steve Grasby, co-author of a paper published this month in the journal Geology. "We estimate that the mercury released then could have been up to 30 times greater than today's volcanic activity, making the event truly catastrophic." Grasby is a research scientist at Natural Resources Canada and an adjunct professor at the University of Calgary.

[...]

During the late Permian, the natural buffering system in the ocean became overloaded with mercury contributing to the loss of 95 per cent of life in the sea.

"Typically, algae acts like a scavenger and buries the mercury in the sediment, mitigating the effect in the oceans," says lead-author Dr. Hamed Sanei, research scientist at Natural Resources Canada and adjunct professor at the University of Calgary. "But in this case, the load was just so huge that it could not stop the damage."

[...]

The mercury deposition rates could have been significantly higher in the late Permian when compared with today's human-caused emissions. In some cases, levels of mercury in the late Permian ocean was similar to what is found near highly contaminated ponds near smelters, where the aquatic system is severely damaged, say researchers


Looking more and more like my PT Extinction post needs an update. It has been almost 6 years. (wow) And I have STILL not finished my other paleo posts. :(