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 Supercomputing helps researchers understand Earth's interior
23.05.2017 | University of Illinois College of Liberal Arts & Sciences

nachricht How is climate change affecting fauna in the Arctic?
22.05.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

Im Focus: Bacteria harness the lotus effect to protect themselves

Biofilms: Researchers find the causes of water-repelling properties

Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

 
Latest News

Scientists propose synestia, a new type of planetary object

23.05.2017 | Physics and Astronomy

Zap! Graphene is bad news for bacteria

23.05.2017 | Life Sciences

Medical gamma-ray camera is now palm-sized

23.05.2017 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>