A University of Colorado at Boulder study indicates meltwater periodically overwhelms the interior drainpipes of Alaska's Kennicott Glacier and causes it to lurch forward, similar to processes that may help explain the acceleration of glaciers observed recently on the Greenland ice sheet that are contributing to global sea rise.
According to CU-Boulder Professor Robert Anderson of the Institute of Arctic and Alpine Research, the amount of water passing through conduits inside and underneath the Kennicott Glacier increases during seasonal melting and also following annual flooding from a nearby lake. The addition of excess water from melting and flooding causes water to back up into a honeycomb of passages inside the glacier, he said, suggesting the resulting increase in water pressure causes the glacier to slide more rapidly down its bedrock valley.
"The phenomenon is similar to the plumbing system of a house that is incapable of handling excess water or waste, causing it to back up," said Anderson. "This is a feedback we are still trying to understand and one that has big implications for understanding the dynamics of glaciers and ice sheets, including the behavior of outlet glaciers on the Greenland ice sheet."
A paper on the subject appears in the January edition of the new monthly scientific journal, Nature Geoscience. The study was authored by former CU-Boulder graduate student Timothy Bartholomaus, Robert Anderson, and INSTAAR's Suzanne Anderson. Robert Anderson is a faculty member in the CU-Boulder geological sciences department and Suzanne Anderson is a faculty member the geography department.
The sliding eventually halts when the moving glacier opens up spaces in its bed that can accommodate some of the excess water, helping to relieve the water pressure, the authors said. In addition, high rates of water flow eventually enlarge the conduits and ducts permeating the glacier, "melting them back and allowing more water to bleed from the system, further decreasing the pressure," said Robert Anderson.
The Kennicott Glacier roughly doubled its normal 1-to-2 feet of movement per day during the 2006 sliding episodes tied to water pressure, said Anderson. When the glacier responded to a 2006 "outburst" flood -- when water from Hidden Creek Lake adjacent to the glacier rushed into the sub-glacial tunnel system and released an estimated 10 billion gallons of water under the glacier -- the pace ramped up to nearly 9 feet a day for the duration of the two-day period.
The team used GPS receivers positioned on the glacier as well as pressure gauges, temperature sensors, sonic distance measuring sensors and electrical conductivity probes. The conductivity levels in the water draining out of the glacier rose after backpressure in the glacier dissipated and expelled water high in chloride ions abundant in the salty bedrock beneath the ice, said co-author Suzanne Anderson.
"Nature essentially provided us with an extra probe to determine these sub-glacial processes, and ultimately provided an additional avenue of support for our model of how this system works," said Robert Anderson. The National Science Foundation funded the research.
An awareness of such glacial dynamics is important information for glaciologists studying the Greenland ice sheet, which is undergoing record surface melt and the subsequent drainage of large volumes of water through the ice sheet and associated outlet glaciers, the researchers said. Some of Greenland's outlet glaciers have sped up from 50 percent to 100 percent during the annual melt season and discharged substantially more ice into the seas, according to recent research led by CU-Boulder glaciologist Konrad Steffen.
"There are a number of catastrophic draining events of slush ponds on the Greenland ice sheet that may well promote increased sliding of the ice sheet as this water is jammed into a sub-glacial pipe system that is ill-prepared for such inputs," Robert Anderson said. "This phenomenon is also relevant to small glaciers around the world, because it may help to explain their nonsteady rates of sliding.
"People are becoming increasingly aware that sea-level rise is a very real problem," he said. "As scientists, we need to acknowledge the role of all of the world's ice masses and to understand the physical mechanisms by which they deliver water to the sea."
Robert Anderson | EurekAlert!
Rare lizard fossil preserved in amber
27.02.2020 | Rheinische Friedrich-Wilhelms-Universität Bonn
The seismicity of Mars
25.02.2020 | ETH Zurich
Researchers at the University of Bayreuth have discovered an unusual material: When cooled down to two degrees Celsius, its crystal structure and electronic properties change abruptly and significantly. In this new state, the distances between iron atoms can be tailored with the help of light beams. This opens up intriguing possibilities for application in the field of information technology. The scientists have presented their discovery in the journal "Angewandte Chemie - International Edition". The new findings are the result of close cooperation with partnering facilities in Augsburg, Dresden, Hamburg, and Moscow.
The material is an unusual form of iron oxide with the formula Fe₅O₆. The researchers produced it at a pressure of 15 gigapascals in a high-pressure laboratory...
Study by Mainz physicists indicates that the next generation of neutrino experiments may well find the answer to one of the most pressing issues in neutrino physics
Among the most exciting challenges in modern physics is the identification of the neutrino mass ordering. Physicists from the Cluster of Excellence PRISMA+ at...
Fraunhofer researchers are investigating the potential of microimplants to stimulate nerve cells and treat chronic conditions like asthma, diabetes, or Parkinson’s disease. Find out what makes this form of treatment so appealing and which challenges the researchers still have to master.
A study by the Robert Koch Institute has found that one in four women will suffer from weak bladders at some point in their lives. Treatments of this condition...
The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.
Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...
Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.
Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...
12.02.2020 | Event News
16.01.2020 | Event News
15.01.2020 | Event News
28.02.2020 | Materials Sciences
28.02.2020 | Life Sciences
28.02.2020 | Architecture and Construction