Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Melting and refreezing of deep Greenland ice speeds flow to sea, study says

16.06.2014

Findings may shift understanding of ice sheet behavior

Beneath the barren whiteness of Greenland, a mysterious world has popped into view. Using ice-penetrating radar, researchers have discovered ragged blocks of ice as tall as city skyscrapers and as wide as the island of Manhattan at the very bottom of the ice sheet, apparently formed as water beneath the ice refreezes and warps the surrounding ice upwards.


Melting and refreezing at the bottom of ice sheets warps the layer-cake structure above, as seen in this radar image from Greenland.

Credit: Mike Wolovick

The newly revealed forms may help scientists understand more about how ice sheets behave and how they will respond to a warming climate. The results are published in the latest issue of Nature Geoscience.

"We see more of these features where the ice sheet starts to go fast," said the study's lead author, Robin Bell, a geophysicist at Columbia University's Lamont-Doherty Earth Observatory. "We think the refreezing process uplifts, distorts and warms the ice above, making it softer and easier to flow."

The structures cover about a tenth of northern Greenland, the researchers estimate, becoming bigger and more common as the ice sheet narrows into ice streams, or glaciers, headed for the sea. As meltwater at the bottom refreezes over hundreds to thousands of years, the researchers believe it radiates heat into the surrounding ice sheet, making it pick up its pace as the ice becomes softer and flows more easily.

Since the 1970s, and as recently as 1998, researchers flying over the region mistook radar images of these structures for hills. Newer instruments flown during NASA's IceBridge campaign to map ice loss at both poles found the hills to be made of ice instead of rock. Bell, who had discovered similar ice features at the base of the East Antarctic ice sheet, recognized them immediately.

While mapping Antarctica's ice-covered Gamburtsev Mountains in 2008 and 2009, Bell and colleagues discovered extensive melting and refreezing along ridges and steep valley walls of the range. Though researchers had long known that pressure and friction can melt the bottom of ice sheets, no one knew that refreezing water could deform the layer-cake structure above. In a 2011 study in Science, Bell and colleagues proposed that ice sheets can grow from the bottom up, not just from the top-down accumulation of falling snow.

The current study builds on the findings from Antarctica by linking the bottom features to faster ice sheet flow. The researchers looked at Petermann Glacier in the north of Greenland, which made headlines in 2010 when a 100-square mile chunk of ice slipped into the sea. They discovered that Petermann Glacier is sweeping a dozen large features with it toward the coast as it funnels off the ice sheet; one feature sits where satellite data has shown part of the glacier racing twice as fast as nearby ice. The researchers suggest that the refreeze process is influencing the glacier's advance hundreds of miles from where Petermann floats onto the sea.

"Overall, these observations suggest that basal freeze-on is a key control on the large-scale flow of Petermann Glacier, a possibility that has not been explored previously," writes University of Texas researcher Joseph MacGregor in the same issue of Nature Geoscience.

Greenland's glaciers appear to be moving more rapidly toward the sea as climate warms but it remains unclear how the refreeze process will influence this trend, the researchers said.

They expected to find bottom features in the ice sheet's interior, as they did in Antarctica, but did not expect to see features at the edges, where lakes form and rivers flow over the surface, they said. Water from those lakes and rivers appears to fall through crevasses and other holes in the ice to reach the base of the ice sheet, where some of it apparently refreezes. Their discovery indicates that refreezing and deformation at the base of the ice sheet may be far more widespread than previously thought. Bell and her colleagues believe that similar features may come to light as other parts of Greenland and Antarctica are studied in closer detail.

Flying over northern Greenland during the 2011 Ice Bridge season, Kirsty Tinto, a geophysicist at Lamont-Doherty, sat up straight when the radar images began to reveal a deformed layer-cake structure. "When you're flying over this flat, white landscape people almost fall asleep it's so boring—layer cake, layer cake, layer cake," said Tinto, a study coauthor. "But then suddenly these things appear on the screen. It's very exciting. You get a sense of these invisible processes happening underneath."

###

The study was funded by the U.S. National Science Foundation and NASA. Other authors: Indrani Das, Michael Wolovick, Winnie Chu, Timothy Creyts, Nicholas Frearson, Abdulhakim Abdi, all of Lamont-Doherty, and John Paden of Kansas University.

Copies of the paper, "Widespread Persistent Thickening of the East Antarctic Ice Sheet by Freezing from the Base," are available from the authors or from Nature. UK: j.middleton@nature.com US: k.anderson@natureny.com

Scientist contacts:

Robin Bell 845-365-8827 robinb@ldeo.columbia.edu

Kirsty Tinto 845-365-8598 tinto@ldeo.columbia.edu

More information: Kim Martineau, Science Writer, The Earth Institute kmartine@ldeo.columbia.edu 646-717-0134

The Earth Institute, Columbia University mobilizes the sciences, education and public policy to achieve a sustainable earth. http://www.earth.columbia.edu.

Lamont-Doherty Earth Observatory seeks fundamental knowledge about the origin, evolution and future of the natural world. Its scientists study the planet from its deepest interior to the outer reaches of its atmosphere, on every continent and in every ocean, providing a rational basis for the difficult choices facing humanity. http://www.ldeo.columbia.edu

Kim Martineau | Eurek Alert!

Further reports about: Antarctic Antarctica Earth Glacier Greenland Melting structures

More articles from Earth Sciences:

nachricht NASA sees the end of ex-Tropical Cyclone 02W
21.04.2017 | NASA/Goddard Space Flight Center

nachricht New research unlocks forests' potential in climate change mitigation
21.04.2017 | Clemson 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: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>