Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Meltwater from the Greenland ice sheet releasing faster

05.01.2016

The firn layers of the Greenland ice sheet might store less meltwater than previously assumed. Researchers from the USA, Denmark and the University of Zurich fear that this could lead to increased release of the meltwater into the oceans.

The near-surface layers of the Greenland ice sheet are made up of snow that is gradually being converted into glacier ice. In Greenland this firn layer is up to 80 m thick.


Meltwater rivers on the Greenland ice sheet.

Dirk van As, Geological Survey of Denmark and Greenland

As researchers from Denmark, the USA and the University of Zurich have demonstrated, the current atmospheric warming is changing this firn layer such that resulting meltwater is being released faster than previously anticipated.

“Basically our research shows that the firn reacts fast to a changing climate. Its ability to limit mass loss of the ice sheet by retaining meltwater could be smaller than previously assumed”, sums up Horst Machguth, lead author of the study by the University of Zurich.

The researchers travelled to Greenland to investigate the impact of recent atmospheric warming on the structure of near-surface snow and ice layers, called firn. Over the course of three expeditions on the ice sheet, the researchers traversed several hundred kilometres to map the structure of the firn layers with a radar unit and by drilling regularly-spaced firn cores.

Firn layer acts sponge-like

Earlier research has shown that the firn layer acts similar to a sponge. It stores meltwater percolating down into the firn from the surface in what are referred to as ‘ice lenses’. “It is unknown how the firn reacted to the recent very warm summer in Greenland. Our research aims to clarify whether the firn was indeed capable of retaining the meltwater, or whether the sponge has been overwhelmed.”

The scientists drilled numerous 20 metre-deep cores to sample the firn, also targeting sites where similar cores had been drilled 15 to 20 years ago. At many locations, a comparison of the new and old cores revealed substantially more ice lenses than in the past and that the firn stored the meltwater similar to a sponge. But this was not the case everywhere. Cores drilled at lower elevations indicated that the exceptional amounts of meltwater formed a surprisingly massive ice layer directly below the ice sheet surface.

Meltwater no longer percolating

“It appears that the intensive and repeated entry of meltwater formed numerous ice lenses, which ultimately hindered percolation of further meltwater”, says Dirk van As, a co-author of the study from the Geological Survey in Denmark and Greenland. As a result, the many small lenses grew to form an ice layer of several meters in thickness that now acts as a lid on top of otherwise sponge-like firn.

Radar measurements identified that this layer was continuous over dozens of kilometers. New meltwater, hitting that lid of ice was unable to percolate into the firn and remained at the surface. Satellite imagery shows that the water prevented from percolating collected at the surface, where it formed rivers that flow towards the margin of the ice sheet.

“In contrast to storing meltwater in porous firn, this mechanism increases runoff from the ice sheet”, explains Mike MacFerrin, second-author of the study and a researcher at the University of Colorado at Boulder.

“This process has not previously been observed in Greenland. The total extent of this ice lid capping the ice sheet firn remains unknown. For this reason, the amount of additional ice sheet runoff associated with this newly observed process cannot yet be quantified.” However, similar changes in firn structure have already been observed in the Canadian Arctic, which leads to the conclusion that this phenomenon could be widespread.

Literature:
Machguth, H., M. MacFerrin, D. van As, J. E. Box, C. Charalampidis, W. Colgan, R. S. Fausto, H. A. J. Meijer, E. Mosley-Thompson and R. S. W. van de Wal. Greenland meltwater storage in firn limited by near-surface ice formation. Nature Climate Change. Doi: 10.1038/NCLIMATE2899
http://nature.com/articles/doi:10.1038/nclimate2899

Contacts:
Horst Machguth
World Glacier Monitoring Service
Department of Geography
University of Zurich.
Phone: +41446355119
Email: horst.machguth@geo.uzh.ch

Dirk van As
Geological Survey of Denmark and Greenland (GEUS) Copenhagen, Denmark
Phone: +4591333818
Email: dva@geus.dk

Michael MacFerrin
Cooperative Institute for Research in Environmental Sciences (CIRES)
University of Colorado at Boulder, USA
Phone: 1-303-565-9920
Email: michael.macferrin@colorado.edu

Beat Müller | Universität Zürich
Further information:
http://www.uzh.ch/

More articles from Earth Sciences:

nachricht Predicting eruptions using satellites and math
28.06.2017 | Frontiers

nachricht NASA sees quick development of Hurricane Dora
27.06.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

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...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

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

Supersensitive through quantum entanglement

28.06.2017 | Physics and Astronomy

X-ray photoelectron spectroscopy under real ambient pressure conditions

28.06.2017 | Physics and Astronomy

Mice provide insight into genetics of autism spectrum disorders

28.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>