Tech & Science
Technology and Science news from Boulder, Colorado
CU Boulder research team finds massive crevasses and bendable ice affect stability of Antarctic ice shelf
Dec 7th
Gaping crevasses that penetrate upward from the bottom of the largest remaining ice shelf on the Antarctic Peninsula make it more susceptible to collapse, according to University of Colorado Boulder researchers who spent the last four Southern Hemisphere summers studying the massive floating sheet of ice that covers an area twice the size of Massachusetts.
But the scientists also found that ribbons running through the Larsen C Ice Shelf – made up of a mixture of ice types that, together, are more prone to bending than breaking – make the shelf more resilient than it otherwise would be.
The research team from CU-Boulder’s Cooperative Institute for Research in the Environmental Sciences presented the findings Dec. 6 at the American Geophysical Union’s annual meeting in San Francisco.
The Larsen C Ice Shelf is all that’s left of a series of ice shelves that once clung to the eastern edge of the Antarctic Peninsula and stretched into the Weddell Sea. When the other shelves disintegrated abruptly – including Larsen A in January 1995 and Larsen B in February 2002 – scientists were surprised by the speed of the breakup.
Researchers now believe that the catastrophic collapses of Larsen A and B were caused, at least in part, by rising temperatures in the region, where warming is increasing at six times the global average. The Antarctic Peninsula warmed 4.5 degrees Fahrenheit since the middle of the last century.
The warmer climate increased meltwater production, allowing more liquid to pool on top of the ice shelves. The water then drained into surface crevasses, wedging them open and cracking the shelf into individual icebergs, which resulted in rapid disintegration.
But while the meltwater may have been responsible for dealing the final blow to the shelves, researchers did not have the opportunity to study how the structure of the Larsen A and B shelves may have made them more vulnerable to drastic breakups – or protected the shelves from an even earlier demise.
CU-Boulder researchers did not want to miss the same opportunity on the Larsen C shelf, which covers more than 22,000 square miles of sea.
“It’s the perfect natural laboratory,” said Daniel McGrath, a doctoral student in the Department of Geography and part of the CIRES research team. “We wanted to study this shelf while it’s still stable in order to get a better understanding of the processes that affect ice shelf stability.”
McGrath worked with CIRES colleagues over the last four years to study the Larsen C shelf in order to better understand how the warming climate may have interacted with the shelf’s existing structure to increase its vulnerability to a catastrophic collapse.
McGrath presented two of the group’s key findings at the AGU meeting. The first was the role that long-existing crevasses that start at the base of the shelf and propagate upward – known as basal crevasses – play in making the shelf more vulnerable to disintegration. The second relates to the way a type of ice found in areas called suture zones may be protecting the shelf against a breakup.
The scientists used ground penetrating radar to map out the basal crevasses, which turn out to be massive. The yawning cracks can run for several miles in length and can penetrate upwards for more than 750 feet. While the basal crevasses have been a part of Larsen C for hundreds of years, the interaction between these features and a warming climate will likely make the shelf more susceptible to future disintegration. “They likely play a really important role in ice-shelf disintegration, both past and future,” McGrath said.
The research team also studied the impact of suture zones in the ice shelf. Larsen C is fed by 12 distinct glaciers, which dump a steady flow of thick ice into the shelf. But the promontories of land between the glacial outlets, where ice does not flow into the shelf, allow for the creation of ribbon-like suture zones, which knit the glacial inflows together and which turn out to be important to the ice shelf’s resilience. “The ice in these zones really holds the neighboring inflows together,” McGrath said.
The suture zones get their malleable characteristic from a combination of ice types. A key component of the suture zone mixture is formed when the bottoms of the 12 glacial inflows begin to melt. The resulting freshwater is more buoyant than the surrounding seawater, so it rises upward to the relatively thinner ice zones between the glacial inflows, where it refreezes on the underside of the shelf and contributes to the chaotic ice structure that makes suture zones more flexible than the surrounding ice.
It turns out that the resilient characteristics of the suture zones keep cracks, including the basal crevasses, from spreading across the ice shelf, even where the suture zone ice makes up a comparatively small amount of the total thickness of the shelf. The CIRES team found that at the shelf front, where the ice meets the open sea, suture zone ice constitutes only 20 percent of the total thickness of the shelf but was still able to limit the spread of rifts through the ice. “It’s a pretty small part of the total ice thickness, and yet, it still has this really important role of holding the ice shelf together,” McGrath said.
Other CU researchers involved in the Larsen C project were Konrad Steffen, former director of CIRES; Ted Scambos, of CIRES and CU-Boulder’s National Snow and Ice Data Center; Harihar Rajaram, of the Department of Civil Engineering; and Waleed Abdalati, of CIRES.
CU team receives $9.2 million DOE grant to engineer E. coli into biofuels
Dec 4th
“This is a fantastic opportunity to take what we have worked on for the past decade to the next level,” said team leader Ryan Gill, a fellow of CU-Boulder’s Renewable and Sustainable Energy Institute, or RASEI. “In this project, we will develop technologies that are orders of magnitude beyond where we are currently.”
The team is working with a non-pathogenic strain of E. coli. Among the microbe’s more than 4,000 genes, the team is searching for a small set and how it can be manipulated in a combination of on and off states to change the bacteria’s behavior.
“E. coli is not going to want to make your biofuel at all,” said Gill, who’s also a CU-Boulder associate professor of chemical and biological engineering. “It doesn’t do that naturally. It’s programmed with thousands of genes controlling how it replicates. We’re figuring out what control structure we need to rewire in the bug to make it do what we want, not what it wants.”
Included in the team are Rob Knight, CU-Boulder associate professor of chemistry and biochemistry; Pin-Ching Maness, principal scientist at DOE’s National Renewable Energy Laboratory, or NREL; and Adam Arkin, physical biosciences director at DOE’s Lawrence Berkeley National Laboratory.
The researchers hope to engineer the production of ethylene and isobutanol in the modified E. coli. The two compounds are widely used commodities that can be converted into gasoline among other chemicals.
The greatest challenge is harnessing an efficient and inexpensive process that competes with abundant and low-cost fossil fuels like oil, according to Gill.
“Microorganisms and their genomes are incredibly complex machines,” said Gill. “The first step alone — of pinpointing the part of the E. coli genome that can help us make biofuels or other chemicals on a cost-competitive basis — is a daunting challenge. Then we have to determine if the results we want will take one year or decades, $5 million or $500 million.”
The team will be able to simultaneously identify numerous E. coli genes and the results of turning these genes on or off using advanced technologies. Many of the technologies have been developed by the researchers’ own labs.
The grant is the first of its kind from the DOE’s Office of Biological and Environmental Research and was awarded to only seven other research groups including teams led by MIT, Purdue University and the J. Craig Venter Institute.
In 2011, CU’s Technology Transfer Office named Gill an inventor of the year. In 2005, Gill won a National Science Foundation CAREER Award as well as a National Institutes of Health K25 Career Development Award for genomics research and teaching.
CU Boulder study: Alaska’s iconic Columbia Glacier expected to stop retreating in 2020
Nov 26th
The wild and dramatic cascade of ice into the ocean from Alaska’s Columbia Glacier, an iconic glacier featured in the documentary “Chasing Ice” and one of the fastest moving glaciers in the world, will cease around 2020, according to a study by the University of Colorado Boulder.
A computer model predicts the retreat of the Columbia Glacier will stop when the glacier reaches a new stable position — roughly 15 miles upstream from the stable position it occupied prior to the 1980s. The team, headed by lead author William Colgan of the CU-Boulder headquartered Cooperative Institute for Research in Environmental Sciences, published its results today in The Cryosphere, an open access publication of the European Geophysical Union.
The Columbia Glacier is a large (425 square miles), multi-branched glacier in south-central Alaska that flows mostly south out of the Chugach Mountains to its tidewater terminus in Prince William Sound.
Warming air temperatures have triggered an increase in the Columbia Glacier’s rate of iceberg calving, whereby large pieces of ice detach from the glacier and float into the ocean, according to Colgan. “Presently, the Columbia Glacier is calving about 2 cubic miles of icebergs into the ocean each year — that is over five times more freshwater than the entire state of Alaska uses annually,” he said. “It is astounding to watch.”
The imminent finish of the retreat, or recession of the front of the glacier, has surprised scientists and highlights the difficulties of trying to estimate future rates of sea level rise, Colgan said. “Many people are comfortable thinking of the glacier contribution to sea level rise as this nice predictable curve into the future, where every year there is a little more sea level rise, and we can model it out for 100 or 200 years,” Colgan said.
The team’s findings demonstrate otherwise, however. A single glacier’s contribution to sea level rise can “turn on” and “turn off” quite rapidly, over a couple of years, with the precise timing of the life cycle being difficult to forecast, he said. Presently, the majority of sea level rise comes from the global population of glaciers. Many of these glaciers are just starting to retreat, and some will soon cease to retreat.
“The variable nature and speed of the life cycle among glaciers highlights difficulties in trying to accurately predict the amount of sea level rise that will occur in the decades to come,” Colgan said.
The Columbia Glacier was first documented in 1794 when it appeared to be stable with a length of 41 miles. During the 1980s it began a rapid retreat and by 1995 it was only about 36 miles long. By late 2000 it was about 34 miles long.
The loss of a massive area of the Columbia Glacier’s tongue has generated a tremendous number of icebergs since the 1980s. After the Exxon Valdez ran aground while avoiding a Columbia Glacier iceberg in 1989, significant resources were invested to understand its iceberg production. As a result, Columbia Glacier became one of the most well-documented tidewater glaciers in the world, providing a bank of observational data for scientists trying to understand how a tidewater glacier reacts to a warming climate.
Motivated by the compelling imagery of the Columbia Glacier’s retreat documented in the Extreme Ice Survey — James Balog’s collection of time-lapse photography of disappearing glaciers around the world — Colgan became curious as to how long the glacier would continue to retreat. To answer this question, the team of researchers created a flexible model of the Columbia Glacier to reproduce different criteria such as ice thickness and terminus extent.
The scientists then compared thousands of outputs from the computer model under different assumptions with the wealth of data that exists for the Columbia Glacier.
The batch of outputs that most accurately reproduced the well-documented history of retreat was run into the future to predict the changes the Columbia Glacier will most likely experience until the year 2100. The researchers found that around 2020 the terminus of the glacier will retreat into water that is sufficiently shallow to provide a stable position through 2100 by slowing the rate of iceberg production.
The speediness of the glacier’s retreat is due to the unique nature of tidewater glaciers, Colgan said. When warming temperatures melt the surface of a land glacier, the land glacier only loses its mass by run-off. But in tidewater glaciers, the changes in ice thickness resulting from surface melt can create striking changes in ice flow, triggering an additional dynamic process for retreat.
The dynamic response of the Columbia Glacier to the surface melt will continue until the glacier reaches its new stable position in 2020, at roughly 26 miles long. “Once the dynamic trigger had been pulled, it probably wouldn’t have mattered too much what happened to the surface melt — it was just going to continue retreating through the bedrock depression upstream of the pre-1980s terminus,” Colgan said.
Colgan next plans to attempt to use similar models to predict when the Greenland glaciers — currently the major contributors to sea level rise — will “turn off” and complete their retreats.
The future for the Columbia Glacier, however, looks bleak. “I think the hope was that once we saw climate change happening, we could act to prevent some irreversible consequences,” Colgan said, “but now we are only about eight years out from this retreat finishing — it is really sad. There is virtually no chance of the Columbia Glacier recovering its pre-retreat dimensions on human time-scales.”
The study was funded by NASA, and co-authors on the paper include W. Tad Pfeffer of CU-Boulder’s Institute of Arctic and Alpine Research, Harihar Rajaram of the CU-Boulder Department of Civil, Environmental, and Architectural Engineering, Waleed Abdalati of the National Aeronautic and Space Administration in Washington, D.C., and Balog of the Extreme Ice Survey in Boulder, Colo.
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