Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

UNH scientist co-authors report in Nature showing movement of glacier has doubled speed

03.12.2004


The world’s fastest glacier, Greenland’s Jakobshavn Isbrae, doubled its speed between 1997 and 2003. The rapid movement of ice from land into the sea provides key evidence of newly discovered relationships between ice sheets, sea level rise and climate warming.



The findings were reported in the journal Nature on December 2, 2004. Co-authoring the study was University of New Hampshire glaciologist Mark Fahnestock of the Institute for the Study of Earth, Oceans, and Space (EOS).

The researchers found the glacier’s sudden speed-up also coincides with very rapid thinning, indicating loss of ice of up to 15 meters (16.4 yards) in thickness per year after 1997. Along with increased rates of ice flow and thinning, the floating ice that extends from the mouth of the glacier into the ocean, called the ice tongue, began retreating in 2000, breaking up almost completely by May 2003.


The authors began looking at the flow of this glacier using satellite pictures after pronounced thinning was measured by a NASA aircraft.

The satellite imagery revealed the dramatic acceleration. Fahnestock found this signal to be quite striking. "This speedup is the most dramatic change observed in a large glacier to date", Fahnestock said. "Observing a doubling of the flow of one of the large rivers of ice draining the Greenland Ice Sheet in such a short time raises questions about the nature and stability of the ice sheet,"

The NASA-funded study relies on data from satellites and airborne lasers to derive ice movements. The study’s lead author, Ian Joughin, conducted much of this research while working at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. Joughin is currently a glaciologist at the Applied Physics Laboratory at the University of Washington, Seattle. Co-authors include Waleed Abdalati, a senior scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md., and Fahnestock.

"In many climate models glaciers are treated as responding slowly to climate change," Joughin said. "In this study we are seeing a doubling of output beyond what most models would predict. The ice sheets can respond rather dramatically and quickly to climate changes." "This finding suggests the potential for more substantial thinning in other glaciers in Greenland," Abdalati added. "Other glaciers have thinned by over a meter a year, which we believe is too much to be attributed to melting alone. We think there is a dynamic effect where the glaciers are accelerating as warming causes conditions to change at the boundaries of these ice streams."

The researchers used satellite and other data to observe large changes in both speeds and thickness between 1985 and 2003. The data showed that the glacier slowed down from a velocity of 6700 meters (4.2miles) per year in 1985 to 5700 meters (3.5 miles) per year in 1992. This latter speed remained somewhat constant until 1997. By 2000, the glacier had sped up to 9400 meters (5.8 miles) per year, topping out with the last measurement in spring 2003 at 12,600 meters (7.7miles) per year.

Airborne laser altimetry measurements of Jakobshavn’s surface elevation, made previously by researchers at NASA’s Wallops Flight Facility, showed a thickening or building up of the glacier from 1991 to 1997, coinciding closely with the glacier’s slow-down. Similarly, the glacier began thinning by as much as 15 meters (16.4 yards) a year just as its velocity began to increase between 1997 and 2003.

The authors used synthetic aperture radar (SAR) data from Canada’s RADARSAT and the European Space Agency’s European Remote Sensing Satellites to measure the glacier’s velocity in 1992, 1994, 1995 and 2000. They also tracked distinct features in NASA Landsat image pairs to determine velocities in 2001, 2002 and 2003. Speeds from 1997 were determined using airborne laser survey data. Researchers at the University of Maine and Ohio State University used airborne photographs to calculate historical 1985 velocities.

The acceleration comes at a time when the floating ice near the glacier’s calving front has shown some unusual behavior. Despite its relative stability from the 1950s through the 1990s, the glacier’s ice tongue began to break apart in 2000, leading to almost complete disintegration in 2003. The tongue’s thinning and break up likely reduced its restraining effects on the ice behind it, as several speed increases coincided with losses of sections of the ice tongue as it broke up. Recent NASA-funded research in the Antarctic Peninsula showed similar increases in glacier flow following the Larson B ice shelf break-up.

Jakobshavn Isbrae is Greenland’s largest outlet glacier, draining 6.5 percent of Greenland’s ice sheet area. The ice stream’s speed-up and near-doubling of ice flow from land into the ocean is important because this one glacier has increased the rate of sea level rise by about .06 millimeters per year, or roughly 4 percent of the 20th century rate of sea level increase.

David Sims | EurekAlert!
Further information:
http://www.unh.edu

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>