Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rapidly accelerating glaciers may increase how fast the sea level rises

15.11.2005


Satellite images show that, after decades of stability, a major glacier draining the Greenland ice sheet has dramatically increased its speed and retreated nearly five miles in recent years. These changes could contribute to rapid melting of the Greenland ice sheet and cause the global sea level to rise faster than expected, according to researchers studying the glacier.



A paper describing these findings will be published this month in Geophysical Research Letters. The study focused on the Helheim glacier, one of the largest outlet glaciers in Greenland. Warming air and sea temperatures in the area likely caused the glacier to speed up, said Slawek Tulaczyk, associate professor of Earth sciences at the University of California, Santa Cruz, and a coauthor of the paper.

The Greenland ice sheet contains enough water to raise global sea levels by 15 to 20 feet. Although the entire ice sheet is unlikely to melt in this century, even a small change in the rate of melting could inundate low-lying coastal plains and add enough fresh water to the North Atlantic to change ocean circulation patterns, Tulaczyk said.


Ian Howat, a UCSC doctoral candidate in Earth sciences and first author on the paper, said changes such as this could have dramatic implications for climate models. Scientists use complex mathematical models to predict how climate, sea level, and ocean circulation will change in response to growing levels of greenhouse gases in the atmosphere.

"Current models treat the ice sheet like it’s just an ice cube sitting up there melting, and we’re finding it’s not that simple," Howat said.

The researchers used satellite images to determine the movement and retreat of Helheim glacier. Howat tracked the positions of glacial surface features to assess how fast the glacier moved between satellite fly-bys. Satellite images dating back as far as the 1970s show that the front of the glacier has remained in the same place for decades. But in 2001 it began retreating rapidly, moving back four and a half miles between 2001 and 2005. Howat’s measurements also show that the Helheim glacier has sped up from around 70 feet per day to nearly 110 feet per day and thinned by more than 130 feet since 2001.

As the glacier speeds up and retreats, new factors come into play that cause further acceleration and retreat, Howat said. "This is a very fast glacier, and it’s likely to get faster," he said.

The Helheim glacier is a river of ice that pours from the inland Greenland ice sheet, through a narrow rift in the coastal mountain range, and down into the sea at a rate of several miles per year. In the sea, the glacier’s weight keeps it firmly resting on the bottom, as long as the water depth is less than about nine-tenths of the glacier’s thickness. Where the water is deep enough to cause the end of the glacier to float, its front becomes brittle and crumbles into icebergs, Tulaczyk explained.

Warming disrupts the delicate balance between glacier thickness and water depth by melting and thinning the glacier. Temperatures in Greenland have increased by more than five degrees Fahrenheit (three degrees Celsius) over the last decade. If the glacier thins beyond a critical point, it becomes ungrounded, floats, and rapidly disintegrates.

"Outlet glaciers may have been thinning for over a decade," Howat said. "But it’s only in the last few years that thinning reached a critical point and began drastically changing the glacier’s dynamics."

The retreating front of the glacier causes it to move down the mountain slope more rapidly. This thins the glacier further, which causes upstream parts of the glacier to perceive a steeper slope and begin moving faster, Tulaczyk said.

Many fiords, the channels carved by glaciers flowing into the sea, are deep with a shallow lip in front. Once the glacier floats off this shallow pinning point, it retreats into deeper water, making further disintegration likely. Reduced friction between ice and rock at the glacier bed can also increase glacier speed. Fiords often widen inland, causing the glacier to grate less heavily at the fiord walls and move faster as it retreats. And ice crystals in fast-moving glaciers can realign, further reducing friction, Howat said.

The Helheim glacier’s speedup has already propagated 12.5 miles up the glacier. The center of the Greenland ice sheet is only 150 miles inland, and the researchers worry that the effects of the glacier’s retreat will continue to move inland, ultimately decreasing the thickness of the whole ice sheet.

"If other glaciers in Greenland are responding like Helheim, it could easily cut in half the time it will take to destroy the Greenland ice sheet," Howat said. "This is a process we thought was only happening in Antarctica, and now we’re seeing that it happens really fast in Greenland."

Recent studies have shown that many other glaciers in the southern half of Greenland are retreating. To date, only one other glacier, the Jakobshavn Isbrae glacier in the southwest, has been studied sufficiently to determine that it is speeding up as it retreats. But Tulaczyk expects similar mechanisms are at work in other retreating glaciers.

"Our research provides strong evidence that rapid melting processes such as we observed at the Helheim glacier will play a role in ice sheet reduction, but they are currently not included in the models," Tulaczyk said. "My ultimate goal is to convince ice sheet modelers to incorporate this dynamic process in the models."

Emily Saarman | EurekAlert!
Further information:
http://www.ucsc.edu

More articles from Earth Sciences:

nachricht Turning the Climate Tide by 2020
29.06.2017 | Potsdam-Institut für Klimafolgenforschung

nachricht Predicting eruptions using satellites and math
28.06.2017 | Frontiers

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making Waves

Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.

Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Nanostructures taste the rainbow

29.06.2017 | Physics and Astronomy

New technique unveils 'matrix' inside tissues and tumors

29.06.2017 | Life Sciences

Cystic fibrosis alters the structure of mucus in airways

29.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>