Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Melt down

01.11.2001


Half a century of thinning ice leaves Greenland’s future looking wet.


Thinning on top: the Greenland ice sheet is in retreat.
© SPL


Satellites and planes have been measuring the ice sheet’s thickness for the past decade.
© Geoatlas



There is new evidence that the Greenland ice pack is in retreat. The finding may be a foretaste of still more rapid melting, and in turn, rising sea levels.

The ice sheet over northwest Greenland has thinned by 10-15 cm a year over the past 40 years, two scientists calculate1. The trend indicates "a significant long-term thinning", says one, Niels Reeh, of the Technical University of Denmark.


The sheet is more than 3 km thick in some places. It is the world’s second-largest ice mass after Antarctica. Reeh and Stan Paterson, of Paterson Geophysics in Heriot Bay, British Columbia, Canada, compared historical and modern data. This revealed that thinning has been much more pronounced in northwestern Greenland. In the east, there has been little change.

The reason for the east-west difference is not yet clear. Climate changes that occurred hundreds or even thousands of years ago may have altered the physical properties of the ice sheet. Or, like southern Greenland, the northern sheet may be sliding from east to west. Alternatively, the difference may reflect more recent variations in snowfall and temperatures.

Paterson is convinced that the thinning is due to the Earth’s recent temperature rise: "I’d stick my neck out and say that it’s an effect of global warming." Taken with signs of shrinking sea ice over the North Pole and melting at Greenland’s coast, "it’s just one more thread in the story", he says.

"The general consensus is that the central part of the ice sheet is in balance," cautions climate researcher Ellen Mosley-Thompson, of Ohio State University in Columbus. "But if the thinning is real, and if it were to continue for decades to centuries, that would translate into changes in the ice sheet."

Others are less sure. "Up to today, there’s been no convincing sign of Greenland growing or shrinking overall," says Philippe Huybrechts of the Free University of Brussels in Belgium. In fact, Greenland has bucked climate trends, ending the twentieth century slightly cooler than it began, he adds.

Whatever’s happening now, "all climate models show Greenland warming over the coming century", says Huybrechts. This will cause a rise in sea level of several centimetres. "If the climate were to warm, Greenland will be in bad shape, that’s for sure," Huybrechts says.

Seeking long-term trends

Several decades of measurements are needed to understand ice sheets. Short-term changes in temperature and snowfall can obscure underlying trends. For the past ten years, satellites and planes have been taking accurate measurements of the ice sheet’s thickness. But there are few good records from before 1990.

The researchers also drew on information gathered by the British North Greenland Expedition of 1954-55. This joint project saw scientists - including Paterson - and the British Navy journey 1,200 km across the top of Greenland, measuring altitude at 300 points along the way.

"The only way in was on RAF flying boats to a lake that was only unfrozen in August," recalls Paterson, who was also one of four men to cross Greenland. "In those days it was still a bit of an adventure," he says.

References
  1. Paterson, A.B. & Reeh, N. Thinning of the ice sheet in northwest Greenland over the past forty years. Nature, 414, 60 - 62, (2001).

JOHN WHITFIELD | Nature News Service
Further information:
http://www.nature.com/nsu/011101/011101-13.html
http://www.nature.com/nsu/

More articles from Earth Sciences:

nachricht Multi-year submarine-canyon study challenges textbook theories about turbidity currents
12.12.2017 | Monterey Bay Aquarium Research Institute

nachricht How do megacities impact coastal seas? Searching for evidence in Chinese marginal seas
11.12.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Long-lived storage of a photonic qubit for worldwide teleportation

12.12.2017 | Physics and Astronomy

Multi-year submarine-canyon study challenges textbook theories about turbidity currents

12.12.2017 | Earth Sciences

Electromagnetic water cloak eliminates drag and wake

12.12.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>