Posts tagged Northwestern University
Ice-free Arctic winters could explain amplified warming during Pliocene
Jul 29th
Year-round ice-free conditions across the surface of the Arctic Ocean could explain why the Earth was substantially warmer during the Pliocene Epoch than it is today, despite similar concentrations of carbon dioxide in the atmosphere, according to new research carried out at the University of Colorado Boulder.
The last time researchers believe the carbon dioxide concentration in the atmosphere reached 400 ppm—between 3 and 5 million years ago during the Pliocene—the Earth was about 3.5 to 9 degrees Fahrenheit warmer (2 to 5 degrees Celsius) than it is today. During that time period, trees overtook the tundra, sprouting right to the edges of the Arctic Ocean, and the seas swelled, pushing ocean levels 65 to 80 feet higher.
Scientists’ understanding of the climate during the Pliocene has largely been pieced together from fossil records preserved in sediments deposited beneath lakes and on the ocean floor.
“When we put 400 ppm carbon dioxide into a model, we don’t get as warm a planet as we see when we look at paleorecords from the Pliocene,” said Jim White, director of CU-Boulder’s Institute of Arctic and Alpine Research and co-author of the new study published online in the journal Palaeogeography, Paleoclimatology, Palaeoecology. “That tells us that there may be something missing in the climate models.”
Scientists have proposed several hypotheses in the past to explain the warmer Pliocene climate. One idea, for example, was that the formation of the Isthmus of Panama, the narrow strip of land linking North and South America, could have altered ocean circulations during the Pliocene, forcing warmer waters toward the Arctic. But many of those hypotheses, including the Panama possibility, have not proved viable.
For the new study, led by Ashley Ballantyne, a former CU-Boulder doctoral student who is now an assistant professor of bioclimatology at the University of Montana, the research team decided to see what would happen if they forced the model to assume that the Arctic was free of ice in the winter as well as the summer during the Pliocene. Without these additional parameters, climate models set to emulate atmospheric conditions during the Pliocene show ice-free summers followed by a layer of ice reforming during the sunless winters.
“We tried a simple experiment in which we said, ‘We don’t know why sea ice might be gone all year round, but let’s just make it go away,’ ” said White, who also is a professor of geological sciences. “And what we found was that we got the right kind of temperature change and we got a dampened seasonal cycle, both of which are things we think we see in the Pliocene.”
In the model simulation, year-round ice-free conditions caused warmer conditions in the Arctic because the open water surface allowed for evaporation. Evaporation requires energy, and the water vapor then stored that energy as heat in the atmosphere. The water vapor also created clouds, which trapped heat near the planet’s surface.
“Basically, when you take away the sea ice, the Arctic Ocean responds by creating a blanket of water vapor and clouds that keeps the Arctic warmer,” White said.
White and his colleagues are now trying to understand what types of conditions could bridge the standard model simulations with the simulations in which ice-free conditions in the Arctic are imposed. If they’re successful, computer models would be able to model the transition between a time when ice reformed in the winter to a time when the ocean remained devoid of ice throughout the year.
Such a model also would offer insight into what could happen in our future. Currently, about 70 percent of sea ice disappears during the summertime before reforming in the winter.
“We’re trying to understand what happened in the past but with a very keen eye to the future and the present,” White said. “The piece that we’re looking at in the future is what is going to happen as the Arctic Ocean warms up and becomes more ice-free in the summertime.
“Will we continue to return to an ice-covered Arctic in the wintertime? Or will we start to see some of the feedbacks that now aren’t very well represented in our climate models? If we do, that’s a big game changer.”
CU-Boulder geological sciences Professor Gifford Miller also is a co-author of the study. Researchers from Northwestern University and the National Center for Atmospheric Research also were involved in the study, which was supported by a grant from the National Science Foundation.
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CU study: Bug-eyed lenses capture wide view with no distortion
May 1st
To create the innovative camera, which also allows for a practically infinite depth of field, the scientists used stretchable electronics and a pliable sheet of microlenses made from a material similar to that used for contact lenses. The researchers described the camera in an article published today in the journal Nature.
Conventional wide-angle lenses, such as fisheyes, distort the images they capture at the periphery, a consequence of the mismatch of light passing through a hemispherically curved surface of the lens only to be captured by the flat surface of the electronic detector.
For the digital camera described in the new study, the researchers were able to create an electronic detector that can be curved into the same hemispherical shape as the lens, eliminating the distortion.
“The most important and most revolutionizing part of this camera is to bend electronics onto a curved surface,” said Jianliang Xiao, assistant professor of mechanical engineering at CU-Boulder and co-lead author of the study. “Electronics are all made of silicon, mostly, and silicon is very brittle, so you can’t deform the silicon. Here, by using stretchable electronics we can deform the system; we can put it onto a curved surface.”
Creating a camera inspired by the compound eyes of arthropods — animals with exoskeletons and jointed legs, including all insects as well as scorpions, spiders, lobsters and centipedes, among other creatures — has been a sought-after goal. Compound eyes typically have a lower resolution than the eyes of mammals, but they give arthropods a much larger field of view than mammalian eyes as well as high sensitivity to motion and an infinite depth of field.
Compound eyes consist of a collection of smaller eyes called ommatidia, and each small eye is made up of an independent corneal lens as well as a crystalline cone, which captures the light traveling through the lens. The number of ommatidia determines the resolution and varies widely among arthropods. Dragonflies, for example, have about 28,000 tiny eyes while worker ants have only in the neighborhood of 100.
Imitating the corneal lens-crystalline cone pairings, the camera created by Xiao and his colleagues has 180 miniature lenses, each of which is backed with its own small electronic detector. The number of lenses used in the camera is similar to the number of ommatidia in the compound eyes of fire ants and bark beetles.
The electronics and the lenses are both flat when fabricated, said Xiao, who began working on the project as a postdoctoral researcher in John Roger’s lab at the University of Illinois at Urbana-Champaign. This allows the product to be manufactured using conventional systems.
“This is the key to our technology,” Xiao said. “We can fabricate an electronic system that is compatible with current technology. Then we can scale it up.”
The lens sheet and the electronics sheet are integrated together while flat and then molded into a hemispherical shape afterward. Each individual electronic detector and each individual lens do not deform, but the spaces between the detectors and lenses can stretch and allow for the creation of a new 3-D shape. The electronic detectors are all attached with serpentine filament bridges, which are not compromised as the material stretches and bends.
In the pictures taken by the new camera, each lens-detector pairing contributes a single pixel to the image. Moving the electronic detectors directly behind the lenses — instead of having just one detector sitting farther behind a single lens, as in conventional cameras — creates a very short focal length, which allows for the near-infinite depth of field.
The new paper demonstrates that stretchable electronics can be used as the foundation for a distortion-free hemispherical camera, but commercial production of such a camera may still be years away, Xiao said.
The three other co-lead authors of the paper are Young Min Song, Yizhu Xie and Viktor Malyarchuk, all of the University of Illinois. Other co-authors are Ki-Joong Choi, Rak-Hwan Kim and John Rogers, also of Illinois; Inhwa Jung, of Kyung Hee University in Korea; Zhuangjian Liu, of the Institute of High Performance Computing A*star in Singapore; Chaofeng Lu, of Zhejiang University in China and Northwestern University; Rui Li, of Dalian University of Technology in China; Kenneth Crozier, of Harvard University; and Yonggang Huang, of Northwestern University.
The research was funded by the Defense Advanced Research Projects Agency and the National Science Foundation.
CU news release
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CU-BOULDER ANNOUNCES FINALISTS FOR DEAN OF LEEDS SCHOOL OF BUSINESS
Nov 3rd
Two finalists have been named for the position of dean of the Leeds School of Business at the University of Colorado at Boulder.
The finalists are David L. Ikenberry of the University of Illinois at Urbana-Champaign and Kenneth A. Kavajecz of the University of Wisconsin-Madison, according to William Kaempfer, chair of the search committee and vice provost and associate vice chancellor at CU-Boulder.
The position is expected to be filled during spring 2011.
Ikenberry, who will visit campus Nov. 17-20, is the associate dean of the College of Business at the University of Illinois at Urbana-Champaign. His academic experience dates back to 1990, and he has held faculty and administrative positions at Rice University, the University of Washington and the University of Illinois. He has sat on several external boards and committees. He earned his doctorate at the University of Illinois at Urbana-Champaign.
Ikenberry teaches investment and corporate finance and has been recognized for his excellent work in the classroom as a professor. In 2002, he was named as one of the best instructors in the nation by Business Week.
On Nov. 30-Dec. 3, Kavajecz, associate dean for full-time masters programs and associate dean for the undergraduate program at the University of Wisconsin-Madison’s Wisconsin School of Business, will visit. A former assistant economist with the Board of Governors of the Federal Reserve System’s Division of Monetary Affairs, Kavajecz academic experience dates back to 1996. He has held faculty and administrative positions at Northwestern University, The Wharton School at the University of Pennsylvania and at the University of Wisconsin-Madison. He earned his doctorate at Northwestern University.
Kavajecz has been recognized for excellence in teaching and research. He received teaching awards for both undergraduate and graduate level courses at Northwestern University and at The Wharton School.
In addition to Kaempfer, search committee members include: Michael Stutzer, professor of finance; Phil Shane, professor of accounting; Kai Larsen, associate professor of information systems; Page Moreau, associate professor of marketing; Cathleen Burns, senior instructor of accounting; Victor Fleischer, associate professor of law; Aswad Allen, director of the Leeds School of Business Office of Diversity Affairs; Toni Blodgett, junior accounting major; Aaron Schlagel, master of business administration candidate; Peter Burridge, president and CEO of Greenhouse Partners and member of the Leeds School of Business Board; and John S. Fischer, CEO of Breakthrough Energy LLC and member of the Leeds School of Business Board.
Manuel Laguna, professor of operations and information management, is currently serving as interim dean of the Leeds School of Business. Laguna succeeded Dennis Ahlburg, who accepted the presidency of Trinity University in San Antonio.
SOURCE: CU MEDIA RELEASE
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