Induced anisotropy, fast ice flow and climate change in ice sheets![]() This project dealt with two hot topics in current climatological research on ice sheets, induced anisotropy and fast ice flow, by means of numerical modelling. A new versatile, three-dimensional computer model "Elmer/Ice" for flowing ice masses was developed, which solves the full-Stokes equations. This makes the model in principle applicable to all different types of flowing ice masses, including the vicinity of ice-sheet domes (important in conjunction with ice-core projects), ice streams, transition zones between ice-sheet, ice-stream and ice-shelf flow and also small glaciers. Within Elmer/Ice, induced anisotropy is described by the "CAFFE model". The CAFFE model was applied to the site of the EDML ice core at Kohnen Station in east Antarctica, for which the measured surface velocity and fabrics profile could be reproduced reasonably well. Elmer/Ice with the CAFFE model was applied to a 200 x 200 km window around the Dome Fuji ice core in central east Antarctica. The main findings of the simulations were: (i) the flow regime at Dome Fuji is a complex superposition of vertical compression, horizontal extension and bed-parallel shear; (ii) for an assumed geothermal heat flux of 60 mW/m2 the basal temperature at Dome Fuji reaches the pressure melting point and the basal melting rate is ~0.35 mm/a; (iii) in agreement with observational data, the fabric shows a strong single maximum at Dome Fuji; (iv) as a consequence of spatially variable basal melting conditions (but somewhat contrary to intuition), the basal age tends to be smaller where the ice is thicker and larger where the ice is thinner. The latter result is of great relevance for the consideration of a future drill-site in the area. As a spin-off study, Elmer/Ice was also applied to the Gorshkov crater glacier at Ushkovsky volcano, Kamchatka, which is characterized by an unusually large aspect ratio and a very high geothermal heat flux. Simulations of the Greenland ice sheet were carried out with R. Greve's ice-sheet model SICOPOLIS. It was found that (i) the present-day North-East Greenland Ice Stream (NEGIS) shows basal sliding enhancement by the factor three compared to the surrounding, slowly flowing ice, and (ii) ice-dynamical processes (basal sliding accelerated by surface meltwater) can speed up the decay of the ice sheet significantly, but not catastrophically in the 21st century and beyond. Modelling with Elmer/Ice of the flow regime of the Antarctic drainage system from Dome Fuji to Shirase Glacier is still ongoing. One doctoral thesis (Hakime Seddik) and one master thesis (Shoko Otsu) were
completed at Hokkaido University within this project.
Project membersPrincipal investigatorDr. Ralf Greve Co-investigatorDr. Shin Sugiyama StudentsMr. Hakime Seddik Ms. Shoko Otsu Research collaboratorsDr. Sergio H. Faria Dr. Olivier Gagliardini Dr. Ilka Hamann Dr. Luca Placidi Dr. Thomas Zwinger Research areas
PublicationsSeddik, H., R. Greve, T. Zwinger and L. Placidi. 2011. Placidi, L., R. Greve, H. Seddik and S. H. Faria. 2010. Greve, R. and S. Sugiyama. 2009. Greve, R., L. Placidi and H. Seddik. 2009. Seddik, H. 2008. Seddik, H., R. Greve, L. Placidi, I. Hamann and O. Gagliardini. 2008. Greve, R. and S. Otsu. 2007. Otsu, S. 2007. Zwinger, T., R. Greve, O. Gagliardini, T. Shiraiwa and M. Lyly. 2007. Research funding organisationJapan Society for the Promotion of Science (JSPS). ---------- |