Currently the yearly General Assembly of the European Geological Union takes place in Vienna, Austria. Dr. Olaf Eisen from the German Alfred Wegener Institute presents results from an environmentally friendly measurement method that he and his colleagues used on an Antarctic ice-shelf for the first time in early 2010. It supplies data that are input to models for the ice mass balance and thus permit better forecasting of future changes in the sea level.
The quality of scientific models depends to a decisive degree on the available database. Therefore members of a young investigators group supported by the German Research Foundation (DFG) now applied a special geophysical measurement method, vibroseismics, for data collection in the Antarctic for the first time. “By means of vibroseismic measurements, we would like to find out more about the structure of the ice and thus about the flow characteristics of the Antarctic ice sheet,” explains Dr. Olaf Eisen from the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association. He is head of the LIMPICS young investigators group (Linking micro-physical properties to macro features in ice sheets with geophysical techniques).Eisen now presents first results from geophysical measurement campaign in the Antarctic on the international conference. The objective of the expedition was to determine the internal structure of an ice sheet from its surface by means of geophysical methods. The cooperation partners are the Universities of Bergen (Norway), Swansea (Wales, UK), Innsbruck (Austria) and Heidelberg (Germany) and the Commission for Glaciology of the Bavarian Academy of Sciences and Humanities. For test purposes vibroseismics was used along with proven explosive seismic methods for the first time on an ice sheet.
One of the problems involved in the application of seismic methods on ice sheets is the very porous firn layer, which may be 50 to 100 metres thick. Explosive seismics involves drilling a hole, approximately 10 to 20 metres deep, into the firn to achieve a better coupling between the explosive charge and the surrounding firn or ice. Drilling takes a lot of time and permits only slow progress along the seismic profiles. Vibroseismics entails the generation of seismic waves directly on the surface. For this purpose the vibrator pad of a 16-ton vibroseis truck of the University of Bergen is pressed onto the precompressed firn and set into operation at a defined vibration rate. In contrast to explosive seismic methods, the excited seismic signal is known and can be repeatedly generated as frequently as desired, leading in the end to improved data quality. However, the loss of seismic energy in the porous firn is a disadvantage. Therefore, the scientists compare the explosive seismic and vibroseismic methods quantitatively and in this way want determine how much energy is propagating from the surface through the ice and reflected back to the surface. First data analyses show that vibroseismics is coequal to the classic explosive seismics concerning the amplitude of the waves sent into deeper snow and ice layers. An explicit advantage is the lower effort and thus less time and energy the scientists spend to measure seismic profiles now.
Yngve Kristoffersen, professor of geophysics at the University of Bergen, who provides the vibroseismic equipment, explains: “The successful pilot study opens up a new era for efficient and more environmentally friendly methods for obtaining seismic information on the internal structure of the ice and the bedrock underneath it. This would extend our knowledge about how the ice sheet moves across the bedrock and about the geological structure of the rock under the ice.” Furthermore, in the coming years this method will be applied during pre-site surveys of future geological drill sites under ice shelves, which will contribute to a better understanding of climate history.
The Alfred Wegener Institute conducts research in the Arctic, Antarctic and oceans of the high and mid latitudes. It coordinates polar research in Germany and provides major infrastructure to the international scientific community, such as the research icebreaker Polarstern and stations in the Arctic and Antarctic. The Alfred Wegener Institute is one of the sixteen research centres of the Helmholtz Association, the largest scientific organisation in Germany.
Margarete Pauls | idw
Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute
Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine