Abrupt permafrost thaw increases climate threat, experts say

ScienceDaily (Nov. 30, 2011) — As the Arctic warms, greenhouse gases will be released from thawing permafrost faster and at significantly higher levels than previous estimates, according to survey results from 41 international scientists published in the Nov. 30 issue of the journal Nature.

Permafrost thaw will release approximately the same amount of carbon as deforestation, say the authors, but the effect on climate will be 2.5 times bigger because emissions include methane, which has a greater effect on warming than carbon dioxide.

The survey, led by University of Florida researcher Edward Schuur and University of Alaska Fairbanks graduate student Benjamin Abbott, asked climate experts what percentage of the surface permafrost is likely to thaw, how much carbon will be released and how much of that carbon will be methane. The authors estimate that the amount of carbon released by 2100 will be 1.7 to 5.2 times larger than reported in recent modeling studies, which used a similar warming scenario.

"The larger estimate is due to the inclusion of processes missing from current models and new estimates of the amount of organic carbon stored deep in frozen soils," Abbott said. "There's more organic carbon in northern soils than there is in all living things combined; it's kind of mind boggling."

Northern soils hold around 1,700 billion gigatons of organic carbon, around four times more than all the carbon ever emitted by modern human activity and twice as much as is now in the atmosphere, according to the latest estimate. When permafrost thaws, organic material in the soil decomposes and releases gases such as methane and carbon dioxide.

"In most ecosystems organic matter is concentrated only in the top meter of soils, but when arctic soils freeze and thaw the carbon can work its way many meters down, said Abbott, who studies how carbon is released from collapsed landscapes called thermokarsts -- a process not accounted for in current models. Until recently that deep carbon was not included in soil inventories and it still is not accounted for in most climate models.

"We know about a lot of processes that will affect the fate of arctic carbon, but we don't yet know how to incorporate them into climate models," Abbott said. "We're hoping to identify some of those processes and help the models catch up."

Most large-scale models assume that permafrost warming depends on how much the air above the permafrost is warming. Missing from the models, say the authors, are processes such as the effects of abrupt thawing that can melt an ice wedge, result in collapsed ground and accelerate additional thawing.

"This survey is part of the scientific process, what we think is going to happen in the future, and how we come up with testable hypotheses for future research," Schurr said. "Our survey outlines the additional risk to society caused by thawing of the frozen North and the need to reduce fossil fuel use and deforestation."

By integrating data from previous models with expert predictions the authors hope to provide a frame of reference for scientists studying all aspects of climate change.

"Permafrost carbon release is not going to overshadow fossil fuel emissions as the main driver of climate change" said Schuur, "but it is an important amplifier of climate change."

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by University of Alaska Fairbanks.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Edward A. G. Schuur, Benjamin Abbott. Climate change: High risk of permafrost thaw. Nature, 2011; 480 (7375): 32 DOI: 10.1038/480032a

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Read More

To diagnose heart disease, visualization experts recommend a simpler approach

ScienceDaily (Oct. 27, 2011) — A team of computer scientists, physicists, and physicians at Harvard has developed a simple yet powerful method of visualizing human arteries that may result in more accurate diagnoses of atherosclerosis and heart disease.

The prototype tool, called "HemoVis," creates a 2D diagram of arteries that performs better than the traditional 3D, rainbow-colored model. In a clinical setting, the tool has been shown to increase diagnostic accuracy from 39% to 91%.

Presented Oct. 27 at the IEEE Information Visualization Conference(InfoVis 2011), the new visualization methodoffers insight to clinicians, imaging specialists, engineers, and others in a wide range of fields who need to explore and evaluate complex, branching structures.

"Our goal was to design a visual representation of the data that was as accurate and efficient for patient diagnosis as possible," says lead author Michelle Borkin, a doctoral candidate at the Harvard School of Engineering and Applied Sciences (SEAS). "What we found is that the prettiest, most popular visualization is not always the most effective."

HemoVis takes data from patient-specific blood flow simulations, combined with traditional imaging data, and visually displays a tree diagram of the arteries with areas of disease highlighted to assist in diagnosis.

Tools for artery visualization in both clinical and research settings commonly use 3D models that portray the shape and spatial arrangement of vessels of interest. These complex tools require users to rotate the models to get a complete perspective of spatial orientation.

By contrast, the new visualization requires no such rotation or interaction. The tool utilizes 2D, circumference-adjusted cylindrical cross sections arranged in tree diagrams.

Though this visualization method may seem less high-tech, the team demonstrated through quantitative evaluation with medical experts that the 2D model is actually more accurate and efficient for patient diagnosis.

"In the 3D case, the more complex and branched the arteries were, the longer it took to complete the patient diagnosis, and the lower the accuracy was," Borkin reflects. "In the 2D representation, it didn't matter how many branches we had or how complex they were -- we got consistently fast, accurate results. We weren't expecting that."

Tree diagrams are hardly new, as evolutionary biologists will attest, but scientists in many fields are using them to solve a range of very modern and complex problems. In fact, Borkin applied her own experience in astronomy and physics to transform the concept of visualization for SEAS' Multiscale Hemodynamics research group. In prior work, she had used a very similar type of tree diagram to determine the structure of nebulae in outer space.

"With the consultation and cooperation of clinicians, we were able to draw on fairly well known visualization techniques and principles from computer science to solve a practical clinical problem," says Hanspeter Pfister, Gordon McKay Professor of the Practice of Computer Science at SEAS.

Borkin, Pfister, and their colleagues relied on the input of physicians and others with clinical or laboratory imaging experience throughout the process. Through extensive surveys and interviews, they identified the most popular options for display, accurate layout, and coloring of these arterial projections.

However, Borkin drew on well supported research that is less well known outside the visualization community:

"For years, visualization, computer science, and psychology researchers have identified that color is critical for conveying the value of data, but that the rainbow coloring is not well-attuned to the human visual system."

Accordingly, HemoVis departs from the traditional practice of rainbow color-coding in favor of a graded single-color scheme (red to black) that can represent placement along a continuum.

In tests, diagnostic accuracy, as measured by the proportion of diseased areas identified, increased dramatically with the new color scheme.

Widespread adoption of visual representations like those in HemoVis could have the effect of not only optimizing tasks that are critical for doctors, but also changing long-entrenched mindsets and making scientists "think twice" about their assumptions in data visualization, Borkin says.

"This approach to visualization design and validation is broadly applicable in medicine, engineering, and science," notes Pfister. "We hope that people will use this process as a template for transforming their own visualizations."

Borkin and Pfister acknowledged that while HemoVis represents an important step forward, traditional 3D artery models still play a role, particularly in providing a spatially intuitive tool for surgical planning.

With this in mind, the next steps for this research include further development and optimization of the 2D tool and investigation into how it might complement, rather than replace, its 3D counterpart.

A paper about this work will be published later this year in the journal IEEE Transactions on Visualization and Computer Graphics.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by Harvard University. The original article was written by Mureji Fatunde.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Read More