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 NASA examines Peru's deadly rainfall
24.03.2017 | NASA/Goddard Space Flight Center

nachricht Steep rise of the Bernese Alps
24.03.2017 | Universität Bern

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>