Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scripps Studies Provide New Details About Antarctic Iceberg Detachment

15.06.2005


A helicopter view of the "Loose Tooth," a large area fracturing off the Antarctic Ice Shelf.


A second helicopter is shown flying low over a rift area during a preliminary reconnaissance flight.


Findings show that ice fracturing occurs in episodes and may be tied to changes evolving over seasons

A multifaceted research effort by scientists at Scripps Institution of Oceanography at the University of California, San Diego, and their international colleagues from the University of Tasmania and the Australian Antarctic Division, has resulted in several important new findings about Antarctica and the changing dynamics of its ice structure.

Scientists have been investigating the mechanisms by which Antarctic icebergs detach from the main continental ice sheet because of the importance of determining the future stability of the entire Antarctic ice mass. Little is known about the processes and forces that lead to iceberg detachments, or "calving."



Furthermore, glaciologists believe areas called ice "shelves," floating slabs of ice that extend from the coasts of the Antarctic Ice Sheet out to sea, may be the first indicators of how climate change is affecting the Antarctic continent because of their direct contact with the ocean and their sensitivity to air temperature warming. Some ice shelves are located in conditions that are close to the melting point of ice, and are therefore more sensitive to changes in atmospheric temperature.

Researchers at Scripps’s Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics used a variety of approaches to uncover details of ice shelf "rifting"-ice fracturing that cuts through the entire thickness of an ice shelf and represents the first stage of the process in which icebergs eventually break away from the main ice mass-on East Antarctica’s Amery Ice Shelf. Their findings were recently published in two papers in Geophysical Research Letters.

One paper describes the behavior of the ice shelf rift over a nine-year period, while another paper describes changes over time periods as little as seconds. The researchers captured the information through a variety of data sources, including spaceborne readings from NASA’s Ice, Cloud, and land Elevation Satellite (ICESat), the Multiangle Imaging SpectroRadiometer (MISR) on NASA’s Terra satellite, and synthetic aperture radar. They also coordinated an expedition to Antarctica to deploy global positioning system (GPS) equipment and seismometers directly onto the Antarctic ice, the first time in glaciology that such instruments have been used to study the fracturing of ice shelves.

The first report, led by Helen Amanda Fricker of Scripps, used MISR and other satellite data to monitor the lengths of two rifts on the Amery Ice Shelf from 1996 to 2004. Rifts can lengthen and widen for decades before eventually breaking off.

One area of study focused on a location called the "Loose Tooth," a large area fracturing off the ice shelf that resembles a wobbly tooth about to detach. Historical records show that a Loose Tooth-sized fracture preceded the last significant ice break-off event recorded in 1963 to 1964, demonstrating that iceberg calving is a cyclic process.

The scientists discovered that the Loose Tooth and other rifts grow faster in austral summer (December through March) than in winter. The finding contradicts current assumptions indicating that the forces that cause rifts to propagate are not sensitive to seasonal changes. They also found that the rifts have been widening at a steady annual rate for the past five years.

"There’s a lot we don’t know about how rifts propagate on ice shelves, but our conclusions give us some hints, including the finding that iceberg calving may be temperature and climate change dependent," said Fricker.

"In order to evaluate realistically the evolution of ice shelves under different climate change scenarios, we need to determine how these scenarios might influence the production rate of icebergs," the authors say in the paper.

The second study used GPS measurements and seismometers, which capture vibrations from ground movement, to investigate an active rift area of the Amery Ice Shelf, similar to the way earthquakes are monitored on the San Andreas Fault.

In this unprecedented field study, the researchers recorded "swarms" of seismic activity that showed that rifts widen in short but powerful bursts of acceleration. They found bursts where the rift lengthened by about 600 feet over four hours. They recorded three of these bursts separated by 10 and 24 days, respectively, with the time in between consistent with the ice sheet’s normal, slow widening.

"It was interesting to see this rift just sitting there for a while, and then in short periods of time propagating forward in bursts," said Scripps’ Jeremy Bassis, the lead author of the second study and a participant in the Antarctic field experiment.

Also emerging from both studies are new details of the unique mixture of ice fragments, sea ice and wind-blown snow that fills the rift. This "mélange," as it is called, could be instrumental in advancing the size of the rifts by serving as something of a ratchet in the widening process.

"One of the newest measurements we received from ICESat was for determining the thickness of the mélange," said Fricker, who calculated the thickness of the mélange mixture at more than 278 feet in the rift under study.

Since the mélange is a fusion of elements, it adds further complexity in determining how the ice mass fractures are changing seasonally.

"People have understood that rift propagation is an important phenomenon and now we have new data that can really take us places," said Jean-Bernard Minster, a geophysics professor at Scripps and a coauthor of both studies. "These two reports represent a powerful combination. One allowed us to closely look at the rifts over several years with imagery from space, while the other used field instruments right at the tip of the rift to give us one very detailed season of rift propagation."

A third paper related to this research is being prepared for publication later this year. That study is using scientific models to study glaciological stress and rift widening.

In addition to Fricker, Bassis and Minster, contributing coauthors in the international effort included Richard Coleman of the University of Tasmania and the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE-CRC) and Neal Young of the Australian Antarctic Division and the ACE-CRC in Australia.

The research was supported by NASA, the National Science Foundation, the Australian Government’s Cooperative Research Centre Programme and through an Australian Antarctic Science grant.

Mario Aguilera | EurekAlert!
Further information:
http://www.ucsd.edu

More articles from Earth Sciences:

nachricht NASA finds newly formed tropical storm lan over open waters
17.10.2017 | NASA/Goddard Space Flight Center

nachricht The melting ice makes the sea around Greenland less saline
16.10.2017 | Aarhus 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: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | 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

 
Latest News

Osaka university researchers make the slipperiest surfaces adhesive

18.10.2017 | Materials Sciences

Space radiation won't stop NASA's human exploration

18.10.2017 | Physics and Astronomy

Los Alamos researchers and supercomputers help interpret the latest LIGO findings

18.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>