Saturday, November 26, 2011

The "Martian Chronicles"

The MSL lifted off in an Atlas V rocket the other day.  The rover Curiosity will arrive at the red planet after an approximately 9 month interplanetary cruise.

Check out the video below from NASA television.
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Friday, November 18, 2011

The Wild Missouri River

Given the epic flooding in the Missouri Watershed this past spring and summer, along with flooding in the Mssissippi Basin as well, this article from NOAA is well-timed.  The article gives a superb analysis of the Missouri floods, looking at natural and human contributions to the flooding.

Here's the link to the article: NOAA Article on Missouri River Flooding
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Sunday, November 13, 2011

Waterfront Property Anyone?

Some upcoming investigations into a particularly worrisome Antarctic glacier, the Pine Island Glacier.


International Team to Drill Beneath Massive Antarctic Ice Shelf

ScienceDaily (Nov. 9, 2011) — An international team of researchers funded by NASA and the National Science Foundation (NSF) will travel next month to one of Antarctica's most active, remote and harsh spots to determine how changes in the waters circulating under an active ice sheet are causing a glacier to accelerate and drain into the sea.
The science expedition will be the most extensive ever deployed to Pine Island Glacier. It is the area of the ice-covered continent that concerns scientists most because of its potential to cause a rapid rise in sea level. Satellite measurements have shown this area is losing ice and surrounding glaciers are thinning, raising the possibility the ice could flow rapidly out to sea.
The multidisciplinary group of 13 scientists, led by Robert Bindschadler, emeritus glaciologist of NASA's Goddard Space Flight Center in Greenbelt, Md., will depart from the McMurdo Station in Antarctica in mid-December and spend six weeks on the ice shelf. During their stay, they will use a combination of traditional tools and sophisticated new oceanographic instruments to measure the shape of the cavity underneath the ice shelf and determine how streams of warm ocean water enter it, move toward the very bottom of the glacier and melt its underbelly.
"The project aims to determine the underlying causes behind why Pine Island Glacier has begun to flow more rapidly and discharge more ice into the ocean," said Scott Borg, director of NSF's Division of Antarctic Sciences, the group that coordinates all U.S. research in Antarctica. "This could have a significant impact on global sea-level rise over the coming century."
Scientists have determined the interaction of winds, water and ice is driving ice loss from the floating glacier. Gusts of increasingly stronger westerly winds push cold surface waters away from the continent, allowing warmer waters that normally hover at depths below the continental shelf to rise. The upwelling warm waters spill over the border of the shelf and move along the sea floor, back to where the glacier rises from the bedrock and floats, causing it to melt.
The warm salty waters and fresh glacier melt water combine to make a lighter mixture that rises along the underside of the ice shelf and moves back to the open ocean, melting more ice on its way. How much more ice melts is what the team wants to find out, so it can improve projections of how the glacier will melt and contribute to sea-level rise.
In January 2008, Bindschadler was the first person to set foot on this isolated corner of Antarctica as part of initial reconnaissance for the expedition. Scientists had doubted it was even possible to reach the crevasse-ridden ice shelf. Bindschadler used satellite imagery to identify an area where helicopters could land safely to transport scientists and instrumentation to and from the ice shelf.
"The Pine Island Glacier ice shelf continues to be the place where the action is taking place in Antarctica," Bindschadler said. "It only can be understood by making direct measurements, which is hard to do. We're doing this hard science because it has to be done. The question of how and why it is melting is even more urgent than it was when we first proposed the project over five years ago."
The team will use a hot water drill to make a hole through the ice shelf. After the drill hits the ocean, the scientists will send a camera down into the cavity to observe the underbelly of the ice shelf and analyze the seabed lying approximately 1,640 feet (500 meters) below the ice. Next the team will lower an instrument package provided by oceanographer Tim Stanton of the Naval Postgraduate School in Monterrey, Calif., into the hole. The primary instrument, called a profiler, will move up and down a cable attached to the seabed, measuring temperature, salinity and currents from approximately 10 feet (3 meters) below the ice to just above the seabed.
A second hole will support a similar instrument array fixed to a pole stuck to the underside of the ice shelf. This instrument will measure how ice and water exchange heat. The team also will insert a string of 16 temperature sensors in the lowermost ice to freeze inside and become part of the ice shelf. The sensors will measure how fast heat is transmitted upward through the ice when hot flushes of water enter the ocean cavity.
Sridhar Anandakrishnan, a geophysicist with Pennsylvania State University in University Park, Pa., will study the shape of the ocean cavity and the properties of the bedrock under the Pine Island Glacier ice shelf through a technique called reflective seismology, which involves generating waves of energy by detonating small explosions and banging the ice with instruments resembling sledgehammers. Measurements will be taken in about three dozen spots using helicopters to move from one place to another.
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Monday, November 7, 2011

Changing Levels of Atmospheric Gases

Tropical Forests Fertilized by Nitrogen Air Pollution, Scientists Find

ScienceDaily (Nov. 3, 2011) — Scientists braved ticks and a tiger to discover how human activities have perturbed the nitrogen cycle in tropical forests. Studies at two remote Smithsonian Institution Global Earth Observatory sites in Panama and Thailand show the first evidence of long-term effects of nitrogen pollution in tropical trees.
"Air pollution is fertilizing tropical forests with one of the most important nutrients for growth," said S. Joseph Wright, staff scientist at the Smithsonian Tropical Research Institute in Panama. "We compared nitrogen in leaves from dried specimens collected in 1968 with nitrogen in samples of new leaves collected in 2007. Leaf nitrogen concentration and the proportion of heavy to light nitrogen isotopes increased in the last 40 years, just as they did in another experiment when we applied fertilizer to the forest floor."
Nitrogen is an element created in stars under high temperatures and pressures. Under normal conditions, it is a colorless, odorless gas that does not readily react with other substances. Air consists of more than 75% nitrogen. But nitrogen also plays a big role in life as an essential component of proteins. When nitrogen gas is zapped by lightning, or absorbed by soil bacteria called "nitrogen fixers," it is converted into other "active" forms that can be used by animals and plants. Humans fix nitrogen by the Haber process, which converts nitrogen gas into ammonia -- now a principal ingredient in fertilizers. Today, nitrogen fixation by humans has approximately doubled the amount of reactive nitrogen emitted.
Nitrogen comes in two forms or isotopes: atoms that have the same number of protons but different numbers of neutrons. In the case of nitrogen, the isotopes are 14N and 15N, although only about one in 300 nitrogen atoms is the heavier form. Imagine nitrogen in the ecosystem like a bowl of popcorn. Normally the ratio of popped (light) to unpopped (heavy) kernels stays the same, but when someone starts to eat the popcorn, the lighter, popped kernels get used up first, increasing the ratio of heavy to light kernels (or 15N/14N in the case of the ecosystem). Light nitrogen is lost through nitrate leaching and as gases such as N2, and various forms of nitrous oxides or "noxides," some of which can be important greenhouse gases. In the fertilization study in Panama, mentioned earlier, N2O emissions were tripled.
"Tree rings provide a handy timeline for measuring changes in wood nitrogen content," said Peter Hietz from the Institute of Botany at the University of Natural Resources and Life Sciences in Vienna, who faced down a tiger when sampling trees in a monsoon forest on the Thailand-Myanmar border. "We find that over the last century, there's an increase in the heavier form of nitrogen over the lighter form, which tells us that there is more nitrogen going into this system and higher losses. We also got the same result in an earlier study of tree rings in Brazilian rainforests, so it looks like nitrogen fixed by humans now affects some of the most remote areas in the world."
"The results have a number of important implications," said Ben Turner, staff scientist at STRI. "The most obvious is for trees in the bean family (Fabaceae), a major group in tropical forests that fix their own nitrogen in association with soil bacteria. Increased nitrogen from outside could take away their competitive advantage and make them less common, changing the composition of tree communities."
"There are also implications for global change models, which are beginning to include nitrogen availability as a factor affecting the response of plants to increasing atmospheric carbon dioxide concentrations," said Turner. "Most models assume that higher nitrogen equals more plant growth, which would remove carbon from the atmosphere and offset future warming. However a challenge for the models is that there is no evidence that trees are growing faster in Panama, despite the long-term increases in nitrogen deposition and atmospheric carbon dioxide."
Decades of atmospheric nitrogen deposition have caused major changes in the plants and soils of temperate forests in the U.S. and Europe. Whether tropical forests will face similar consequences is an important question for future research.
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  1. P. Hietz, B. L. Turner, W. Wanek, A. Richter, C. A. Nock, S. J. Wright. Long-Term Change in the Nitrogen Cycle of Tropical Forests. Science, 2011; 334 (6056): 664 DOI:10.1126/science.1211979
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Thursday, November 3, 2011

Ice Age

So who or what exactly caused the most recent ice age and its associated extinctions? Well, the causes of the ice age itself are still being vigorously debated.  But this recent article sheds some light on the extinctions of large terrestrial mammals and other animals that took place.  The article appeared in Science Daily.com.


Humans and Climate Contributed to Extinctions of Large Ice Age Mammals, New Study Finds

ScienceDaily (Nov. 2, 2011) — The genetic history of six large herbivores -- the woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison, and musk ox -- has shown that both climate change and humans were responsible for the extinction or near extinction of large mammal populations within the last 10,000 years. The study, which is the first to use genetic, archeological, and climatic data together to infer the population history of large-bodied Ice Age mammals, will be published in the journal Nature.
The study was led by Professor Eske Willerslev of the Centre for GeoGenetics at the University of Copenhagen and includes an international team of paleontologists, geologists, geneticists and climate modelers including Beth Shapiro, the Shaffer Associate Professor of Biology at Penn State University. The study's findings are expected to shed light on the possible fates of living species of mammals as our planet continues its current warming cycle. The paper will be posted on the journal's Advance Online Publication website on 2 November 2011 at 2:00 p.m. U.S. Eastern time.
"Our findings put a final end to the single-cause theories of these extinctions," said Willerslev. "Our data suggest care should be taken in making generalizations regarding past and present species extinctions; the relative impacts of climate change and human encroachment on species extinctions really depends on which species we're looking at."
Shapiro explained that all six of the species the team studied flourished during the Pleistocene Epoch -- the period of geological time that lasted from about 2 million to 12,000 years ago. "During this time, there were lots of climatic ups and downs -- oscillations between long, warm intervals called interglacial periods, during which the climate was similar to what we have today, followed by long, cold intervals called glacial periods, or ice ages," Shapiro said. "Although these cold-adapted animals certainly fared better during the colder, glacial periods, they still managed to find places where the climate was just right -- refugia -- so that they could survive during the warmer, interglacial periods. Then, after the peak of the last ice age around 20,000 years ago, their luck started to run out. The question is, what changed? Why were these mammals no longer able to find safe refugia where they could survive in a warm climate?"
To answer these questions, the team collected many different types of data to test hypotheses about how, when, and why the woolly rhinoceros, woolly mammoth, and wild horse all went extinct after the last ice age, and why the reindeer, bison, and musk ox were able to survive -- albeit in much more restricted ranges than they could inhabit during the ice ages. "One source of information we used was DNA from the animals themselves," Shapiro explained. "With genetic data, it's possible to estimate when and how much populations were able to grow and shrink as the climate changed and their habitat started to disappear." The team also collected climatic data -- temperature and precipitation patterns -- from both glacial and interglacial periods, as well as archeological data, which they used to study the extent to which early humans may have influenced the survival of these six mammal species. "For example, in locations where animal bones had been cooked or converted into spears, we know that humans lived there and were using them as a resource," Shapiro said. "Even where we don't find evidence that humans were using the animals, if humans and the animals lived in the same place and at the same time, humans could have had some influence on whether the animals survived or not."
In the case of the now-extinct woolly rhinoceros, the scientists found that, in Europe, the ranges of humans and woolly rhinoceros never overlapped. "These data suggest that climate change, and not humans, was the main reason why this particular species went extinct in present-day Europe," Shapiro said. "Still, we expect humans might have played a role in other regions of the world where they did overlap with woolly rhinos, and so further studies will be necessary to test this hypothesis." Much clearer was the evidence that humans did influence, and not always negatively, the population sizes of the five other species -- the woolly mammoth, wild horse, reindeer, bison, and musk ox.
Shapiro explained that population fluctuations for all six species continued until the end of the last ice age -- around 14,000 years ago -- when many of the species simply disappeared. "The take-home message is that during the most recent warming event, when the last ice age faded into the warm interval we have today, something kept these animals from doing what they had always done, from finding alternative refugia -- less-than-ideal, but good-enough chunks of land on which to keep their populations at a critical mass," Shapiro said. "That 'something' was probably us -- humans." During the period when these animals were declining, the human population was beginning its boom, and was spreading out across not only the large-bodied mammals' cold-climate habitats, but also across their warm-climate refuges, changing the landscape with agriculture and other activities. Many large-bodied, cold-adapted mammals, including the horse -- which is considered extinct in the wild and now survives only as a domesticated animal -- suddenly had no alternative living spaces, and, as such, no means to maintain their populations.
"The results of our study suggest that although past warm periods caused these animal species to go through periodic bottlenecks -- evolutionary events during which the size of a population diminishes substantially and stays small for a long time -- they always seemed to bounce back, and to return to their previous habitats as soon as the Earth became cooler again. Then, during the most-recent warming cycle, that trend changed," Shapiro said.
As the climate became warmer after the last ice age, the woolly rhinoceros, woolly mammoth, and wild horse became extinct, and the reindeer, bison, and musk ox may have just been fortunate in avoiding extinction, according to Shapiro. "We couldn't pinpoint what patterns characterize extinct species, despite the large and varying amount of data analyzed," said Eline Lorenzen, from the University of Copenhagen and the first author of the study. "This suggests that it will be challenging for experts to predict how existing mammals will respond to future global climate change -- to predict which species will go extinct and which will survive."
Reindeer managed to find safe habitat in high arctic regions and, today, have few predators or competitors for limited resources. Bison are extinct in Asia, where their populations were extensive during the ice ages, and today they are found only in North America, although a related species survives in small numbers in Europe. Cold-adapted muskoxen now live only in the arctic regions of North America and Greenland, with small introduced populations in Norway, Siberia, and Sweden. Interestingly, if humans had any impact on musk-ox populations, it may have been to help sustain them. Musk-ox populations first became established in Greenland around 5,000 years ago, after which they expanded rapidly, despite having been a major resource for the Paleo-Eskimo population. Today, the animal species survives in large numbers.
Shapiro also said that the findings could help to predict the fate of populations threatened by the climate change and habitat alteration that is happening today. "Our results provide direct evidence that something changed between the most-recent glacial cycle, when many of these species went extinct, and previous glacial cycles, through which they all managed to survive. Although it is clear that climate change drives the dynamics of these species, we, as humans, have to take some of the blame for what happened during this most-recent cycle. It seems that our ancestors were able to change the landscape so dramatically that these animals were effectively cut off from what they needed to survive, even when the human population was small," Shapiro said. "There are many more humans today, and we have changed and are continuing to change the planet in even more important ways."
In addition to Shapiro, Willerslev and Lorenzen, many other scientists contributed to this study. In the United States, contributing authors are from institutions in Utah, California, Texas, Missouri, Maryland, Colorado, Massachusetts, Oregon, and Kansas. The study's international contributors are from institutions in Denmark, Australia, Sweden, Spain, the United Kingdom, the Netherlands, Germany, Norway, Russia, China, and Canada.
The research was funded, in part, by the Leverhulme Trust, the Awards Fund, the Danish National Research Foundation, the Lundbeck Foundation, the Danish Council for Independent Research, and the U.S. National Science Foundation.
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