Unravelling the 'inconvenient truth' of glacier movementJune 30, 2008Predicting climate change depends on many factors not properly included in current forecasting models, such as how the major polar ice caps will move in the event of melting around their edges. This in turn requires greater understanding of the processes at work when ice is under stress, influencing how it flows and moves. The immediate objective is to model the flow of ice sheets and glaciers more accurately, leading in turn to better future predictions of global ice cover for use in climate modeling and forecasting. Progress and future research objectives in the field were discussed at a recent workshop organized by the European Science Foundation (ESF), bringing together glaciologists, geologists, and experts in the processes of cracking under stress in other crystalline materials, notably metals and rocks. The essential problem is that processes at different scales starting from the molecular and going up to whole ice sheets need to be integrated in order to develop models capable of accurate predictions. While the processes at the molecular level inside individual ice crystals are quite well understood, too little attention has been paid to the properties of ice at the scale of each grain, comprising organized groups of crystals. All crystalline solids, including metals, are comprised of grains, which are about 1 to 3 cms across in the case of ice. The grain is fundamental for ice movement, because of the strong mechanical anisotropy (irregularity) of individual ice grains. "These processes are much less understood, and one could say they are more 'messy'," said Paul Bons, who co-chaired the ESF workshop. "The challenge ahead is to convert the insight gained on the effects of grain-scale processes into improved rheological models." Rheology is the study of how materials such as ice or rock flow when forces are applied to them. As Bons noted, such knowledge of grain-level interactions is needed not just to construct better models of ice caps, but also for understanding processes inside the earth's mantle, which could help predict earthquakes and volcanoes. "The interesting thing here is actually the similarity between all these compounds, not the differences," said Bons, himself a geologist. "Essentially the same processes occur in ice, minerals and metals."
The differences lie just in the balance between these processes, with interactions between crystals within grains being more significant in ice than metals or rocks. But as was noted by Sergio Faria, another co-chair, it is important to resolve these issues, since current models can be highly inaccurate in predicting ice flows, as has been found by analysing ice cores drilled into glaciers. "The microstructures observed in ice core samples indicate the deformation mechanisms active in an ice sheet," said Faria. "Depending upon the sort of active mechanisms, the flow of an ice sheet may vary by orders of magnitude. Therefore a precise understanding of ice microstructures - and consequently of active deformation mechanisms - is essential to reduce the current uncertainty in ice sheet flow models." As a result of recent findings, the current approach to ice flow analysis, the so-called 3-layer model, will have to be revised, according to Sepp Kipfstuhl, the ESF conference's third co-convenor. "It was interesting to see at the workshop that the study of microstructures challenges standard models for polar ice, especially the classical 3-layer model and the standard flow law of ice. This is an 'inconvenient truth' that complicates large-scale ice flow models, and hence impacts on climate modeling," said Kipfstuhl." As in all branches of science, this inconvenient truth must be faced head on in order to solve the problem of accurate ice flow prediction, which has become all the more pressing in the light of current concerned over the impact of climate change. European Science Foundation | |||||||||||||||||||||
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Related Ice Flow Current Events and Ice Flow News Articles Glaciers Reveal Martian Climate Has Been Recently Active The prevailing thinking is that Mars is a planet whose active climate has been confined to the distant past. About 3.5 billion years ago, the Red Planet had extensive flowing water and then fell quiet - deadly quiet. It didn't seem the climate had changed much since. Researchers warm up to melt's role in Greenland ice loss In July 2006, researchers afloat in a dinghy on a mile-wide glacial lake in Greenland studied features of the lake and ice 40 feet below. Ten days later the entire contents of the lake emptied through a crack in the ice with a force equaling the pummeling water of Niagara Falls. The entire process only took 90 minutes. Antarctic ice loss Increasing amounts of ice mass have been lost from West Antarctica and the Antarctic peninsula over the past ten years, according to research from the University of Bristol and published online this week in Nature Geoscience. Research finds that Earth's climate is approaching 'dangerous' point NASA and Columbia University Earth Institute research finds that human-made greenhouse gases have brought the Earth's climate close to critical tipping points, with potentially dangerous consequences for the planet. Antarctic Ice Sheet's Hidden Lakes Speed Ice Flow Into Ocean, May Disrupt Climate Just as explorers once searched the vast reaches of Africa's Nile River for clues to its behavior and ultimate source, modern-day scientists are searching Antarctica for its hidden lakes and waterways that can barely be detected at the surface of the ice sheet. West Antarctica's subglacial plumbing system mapped from space A network of rapidly filling and emptying lakes lies beneath at least two of West Antarctica's ice streams, new research suggests. Glaciers not on simple, upward trend of melting Two of Greenland's largest glaciers shrank dramatically and dumped twice as much ice into the sea during a period of less than a year between 2004 and 2005. And then, less than two years later, they returned to near their previous rates of discharge. Greenland ice sheet still losing mass, says new University of Colorado study Data gathered by a pair of NASA satellites orbiting Earth show Greenland continued to lose ice mass at a significant rate through April 2006, and that the rate of loss is accelerating, according to a new University of Colorado at Boulder study. NASA Scientist Claims Warmer Ocean Waters Reducing Ice Worldwide According to a NASA scientist, the pieces to a years-old scientific puzzle have come together to confirm warmer water temperatures are creeping into the Earth's colder areas. Those warm waters are increasing melting and accelerating ice flow in polar areas. Impact of Climate Warming on Polar Ice Sheets Confirmed In the most comprehensive survey ever undertaken of the massive ice sheets covering both Greenland and Antarctica, NASA scientists confirm climate warming is changing how much water remains locked in Earth's largest storehouse of ice and snow. More Ice Flow Current Events and Ice Flow News Articles |
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