MAVI Success Story - Dr. Johannes Freitag, AWI

Dr. Johannes Freitag, AWI Bremerhaven
© Photo AWI Bremerhaven

Dr. Johannes Freitag, AWI Bremerhaven

Analysis of Snow

A snow ball might endure the summer safely in an icebox, but transporting a probe of snow without any changes is another challenge. Dr. Johannes Freitag from the Alfred-Wegener-Institute for Polar and Marine Research (AWI, Bremerhaven) knows: “In principle, the transport of snow is nearly impossible. Especially, if you are interested in the finest structural details like we do.” Apart from the fact that snow reacts to the smallest variation in temperature, the mechanical pressure through the transport is too high.

Therefore, Dr. Freitag brought his laboratory to the antarctical station Kohnen, which is inland 500 kilometers away from the coast near Neumayer station.  With 27 colleagues, he worked on the European Project for Ice Coring in Antarctica EPICA, which tries to elicit more and more old and exact climate data. This was realized by drilling with kilometers range into the ice armor of the continent. The drill core contains air, which is composed in the same way as the atmosphere to the time, when snow was densified into firn and then into ice in a depth of 80 to 100 meters. Only ice is capable of densifying that much, so that any exchange of gas with the atmosphere is impossible. Hence, this icy cage can be ten thousand years older than the air it contains.

Particular MAVI-Module

On their expedition, two micro computer tomographs were used for the first time. The micro computer  tomographs are able to provide exact data. For analyzing the 3D x-ray images, MAVI was used – a modular software system of the Fraunhofer Institute for Industrial Mathematics ITWM. Normally, MAVI captures and quantifies geometrical parameters of microstructures such as foams, fiber-reinforced composites, textiles or concrete, and other building materials. Dr. Katja Schladitz, research associate at the department for image processing, says: »Considered in a structural way, snow is an open-cell foam. So we wrote a particular MAVI module.«

Simulation firn cube
© Photo ITWM

Simulation firn cube

Publications

  • S. Linow, M. W. Hörhold, J. Freitag:
    Grain-Size Evolution of Polar Firn: A New Empirical Grain Growth Parameterization Based on X-ray Microcomputer Tomography Measurements.
    Journal of Glaciology, Volume 58, Number 212, pp. 1545-1552(8), December 2012.
  • C. Redenbach, A. Särkkä, J. Freitag, K. Schladitz:
    Anisotropy Analysis of Pressed Point Processes.
    Advances in Statistical Analysis 93(3), S. 237ff, 2009.