Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quirky glacial behavior explained

30.11.2018

Detailed observations of Greenland's Jakobshavn Isbræ help explain dynamic tidewater glacier speedup and slowdown

In August 2012, in the frigid wilderness of West Greenland, the Jakobshavn Glacier was flowing and breaking off into the sea at record speeds, three times faster than in previous years. An underwater calving event had caused the massive glacier to lose its footing. But the movement was not linear like a runaway train (as previous studies suggested), but dynamic: drastically speeding up, then slowing down after a few days.


Jakobshavn Isbrae during Cassotto's 2012 field campaign. Look closely, a 19-seater tourist helicopter hovers above the ice.

Credit: Ryan Cassotto/CIRES and CU Boulder

Now, a new assessment by a multi-institutional, CIRES-led team has harnessed a novel, highly detailed dataset to identify the factors that caused the speedup and slowdown. As the glacier flowed faster, it became thinner and more unstable--and then, in a twist, a pileup of thick ice replenished the glacier's terminus, slowing it down again.

The work, published today in the Journal of Glaciology, may help scientists better predict how tidewater glaciers contribute to sea level rise.

"As tidewater glaciers, like Jakobshavn Isbræ, thin they become increasingly sensitive to small variations in ice thickness," said Ryan Cassotto, CIRES researcher and lead author of the new study, which was conducted while he was a doctoral student at the University of New Hampshire. "This is because water pressure at the base of the glacier counters pressure from the weight of ice above it, which impacts how fast the glacier flows."

For tidewater glaciers grounded deep below sea level, thicker, heavier ice travels slower, and thinner, lighter ice, faster. It's similar, Cassotto said, to the way different sized cars hydroplane: large, heavy truck tend to be very stable and resist sliding while lightweight, compact cars readily slip."

Autoplay video here of 2012 ice calving

Jakobshavn Isbræ, the subject of James Balog's 2012 documentary "Chasing Ice," produces some of the largest icebergs and fastest speeds in the Arctic. And since iceberg calving contributes significantly to sea level rise, it's critical to understand the glacier dynamics and calving events that produce them, the researchers said.

"Over the last two decades, Jakobshavn Isbræ has discharged more ice than any other glacier in Greenland," said Cassotto. "It alone contributes about three percent of the current rise in global sea level annually."

The research team, which included coauthors from the University of Alaska Fairbanks, the University of Alaska Southeast, the University of New Hampshire, and The Ohio State University, harnessed new techniques to observe the glacier at a level of detail never seen before.

They used instruments called ground-based radar interferometers to observe how the ice surface was deforming, measuring every three minutes. Calving events happen in a matter of minutes and so they often can't be caught by satellite-based instruments that repeat measurements only every 11 days.

Cassotto and his team found the geometry of the fjord bed is critically important to understanding glacier speed, as others have proposed. The new work shows that even small changes at the ends of glaciers, those last several hundred feet moving out toward the ocean, can profoundly affect speed.

Media Contact

Ryan Cassotto, lead researcher
ryan.cassotto@colorado.edu
303-492-1790

 @cubouldernews

http://www.colorado.edu/news 

Ryan Cassotto, lead researcher | EurekAlert!

More articles from Earth Sciences:

nachricht What seabirds can tell us about the tide
30.11.2018 | European Geosciences Union

nachricht Wildfires bring climate’s dark forcings to the stratosphere
27.11.2018 | Max-Planck-Institut für Chemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A golden age for particle analysis

Process engineers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have developed a method which allows the size and shape of nanoparticles in dispersions to be determined considerably quicker than ever before. Based on gold nanorods, they demonstrated how length and diameter distributions can be measured accurately in just one step instead of the complicated series of electron microscopic images which have been needed up until now. Nanoparticles from precious metals are used, for example, as catalysts and contrast agents for diagnosing cancer. The results have been published in the renowned journal Nature Communications (doi: 10.1038/s41467-018-07366-9).

Even in the Middle Ages, gold particles were used to create vibrant red and blue colours, for example to illustrate biblical scenes in stained glass windows....

Im Focus: Successful second round of experiments with Wendelstein 7-X

The experiments conducted from July until November at the Wendelstein 7-X fusion device at the Max Planck Institute for Plasma Physics (IPP) in Greifswald have achieved higher values for the density and the energy content of the plasma and long discharge times of up to 100 seconds – record results for devices of the stellarator type. Meanwhile, the next round of the step-by-step upgrading of Wendelstein 7-X has begun. It is to equip the device for greater heating power and longer discharges. Wendelstein 7-X, the world’s largest fusion device of the stellarator type, is to investigate the suitability of this configuration for use in a power plant.

During the course of the step-by-step upgrading of Wendelstein 7-X, the plasma vessel was fitted with inner cladding since September of last year.

Im Focus: New process discovered: Mere sunlight can be used to eradicate pollutants in water

Advances in environmental technology: You don’t need complex filters and laser systems to destroy persistent pollutants in water. Chemists at Martin Luther University Halle-Wittenberg (MLU) have developed a new process that works using mere sunlight. The process is so simple that it can even be conducted outdoors under the most basic conditions. The chemists present their research in the journal “Chemistry - a European Journal”.

The chemists at MLU rely on electrons moving freely in water, so-called hydrated electrons, to degrade dissolved pollutants.

Im Focus: Ultracold quantum mix

The experimental investigation of ultracold quantum matter makes it possible to study quantum mechanical phenomena that are otherwise hardly accessible. A team led by the Innsbruck physicist Francesca Ferlaino has now succeeded for the first time in mixing quantum gases of the strongly magnetic elements Erbium and Dysprosium and creating a dipolar quantum mixture.

Only a few years ago it seemed unfeasible to extend the techniques of atom manipulation and deep cooling in the ultracold regime to many-valence-electron...

Im Focus: First diode for magnetic fields

Innsbruck quantum physicists have constructed a diode for magnetic fields and then tested it in the laboratory. The device, developed by the research groups led by the theorist Oriol Romero-Isart and the experimental physicist Gerhard Kirchmair, could open up a number of new applications.

Electric diodes are essential electronic components that conduct electricity in one direction but prevent conduction in the opposite one. They are found at the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Inaugural "Virtual World Tour" scheduled for december

28.11.2018 | Event News

Top-class programme at the ROS-Industrial Conference 2018

23.11.2018 | Event News

Optical Coherence Tomography: German-Japanese Research Alliance hosted Medical Imaging Conference

19.11.2018 | Event News

 
Latest News

'Sudoku' X-Ray uncovers movements within opaque materials

30.11.2018 | Materials Sciences

What seabirds can tell us about the tide

30.11.2018 | Earth Sciences

Lasers in material processing: Reducing the risk of X-rays

30.11.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>