Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tides control flow of Antarctic ice streams

22.08.2003



"My observations from a few years ago were that Ice Stream D in the West Antarctic was slowing to about half average speed and then speeding up," says Dr. Sridhar Anandakrishnan, associate professor of geoscience, Penn State. "I thought that the speeding up and slowing down was tied to rising and falling of the ocean tides."

The ice streams in West Antarctica move large amounts of ice downward from the center of the glacier toward the ocean. Most of the glacier rests upon bedrock and/or rubble on land, but part of the glacier floats above the ocean. The grounding line, the line where the glacier stops being grounded and floats, is quite a distance back from the leading edge of the glacier.


Some ice streams are moving rapidly, some are slowing down and others have completely stopped moving. Researchers have looked at a number of ice streams and recently, they discovered that Whillan’s Ice Stream exhibits the most bizarre behavior because it actually stops dead and then slips for a short time, moving large distances, before it stops again.

"We were astonished that a one meter tide variation can bring the ice stream to a halt in such a short period of time and that it can accelerate to full throttle in about one minute," says Robert Bindschadler, lead author of the study and a glaciologist and senior fellow at NASA Goddard Space Flight Center. "It underscores the sensitivity of the system to extremely modest forcing."

The researchers report in today’s (Aug. 22) issue of Science, that there is a clear association between this stick-slip phenomenon and the ocean tide.

Anandakrishnan and Bindschadler working with Richard B. Alley, Evan Pugh professor of geoscience, Penn State; Matt A. King, University of Newcastle, Newcastle Upon Tyne, UK, and Laurence Padman, Earth and Space Research, Seattle, combined data from various ice streams and produced a model of how the tides control the slip stick of ice stream motion. They note that "If there were no tides at all, slip events would be predicted to occur approximately every 12 hours."

However, the movement of the ice streams occurs every 18 and then 6 hours. That is, the stream remains still for 18 hours and then slips for 10 to 30 minutes and halts. Then 6 hours later, the stream slips again and halts. The first slip after 18 hours corresponds to just short of high tide and the second slip is when the tide is falling, but is not low.

"The up stream portion of the ice stream keeps moving all the time," says Anandakrishan. "The tide rises and puts pressure upward on the ice stream. Somewhere in the middle, the ice stream sticks."

Eventually the pressure being exerted on the ice stream bed from above is enough to overcome the sticking point and the stream slips and then halts. The tide continues to rise and then recede still putting pressure on the ice stream until once again the ice slips.

"The motion of the ice streams is not as regular during neap tide because the sea rise is not as high," says Anandakrishnan.

Each day the ocean by the West Antarctic has only one high tide and one low tide separated by 12 hours. The levels of the tides vary on a 28-day cycle creating spring tides of up to 5 feet and neap tides of 16- to 20-inches separated by 14 days.

A’ndrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu/

More articles from Earth Sciences:

nachricht The melting ice makes the sea around Greenland less saline
16.10.2017 | Aarhus University

nachricht WSU researchers document one of planet's largest volcanic eruptions
12.10.2017 | Washington State University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

Im Focus: New nanomaterial can extract hydrogen fuel from seawater

Hybrid material converts more sunlight and can weather seawater's harsh conditions

It's possible to produce hydrogen to power fuel cells by extracting the gas from seawater, but the electricity required to do it makes the process costly. UCF...

Im Focus: Small collisions make big impact on Mercury's thin atmosphere

Mercury, our smallest planetary neighbor, has very little to call an atmosphere, but it does have a strange weather pattern: morning micro-meteor showers.

Recent modeling along with previously published results from NASA's MESSENGER spacecraft -- short for Mercury Surface, Space Environment, Geochemistry and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

Conference Week RRR2017 on Renewable Resources from Wet and Rewetted Peatlands

28.09.2017 | Event News

 
Latest News

A single photon reveals quantum entanglement of 16 million atoms

16.10.2017 | Physics and Astronomy

The melting ice makes the sea around Greenland less saline

16.10.2017 | Earth Sciences

On the generation of solar spicules and Alfvenic waves

16.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>