Induced anisotropy, fast ice flow and climate change in ice sheets

Ice modelling

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 members

Principal investigator

Dr. Ralf Greve
Professor
Institute of Low Temperature Science
Hokkaido University, Sapporo, Japan

Co-investigator

Dr. Shin Sugiyama
Lecturer
Institute of Low Temperature Science
Hokkaido University, Sapporo, Japan

Students

Mr. Hakime Seddik
Doctoral student
Graduate School of Environmental Science and
Institute of Low Temperature Science
Hokkaido University, Sapporo, Japan

Ms. Shoko Otsu
Master student
Graduate School of Environmental Science and
Institute of Low Temperature Science
Hokkaido University, Sapporo, Japan

Research collaborators

Dr. Sergio H. Faria
GZG, Department of Crystallography
University of Göttingen, Germany

Dr. Olivier Gagliardini
Laboratory of Glaciology and Environmental Geophysics, CNRS
Joseph Fourier University, Grenoble, France

Dr. Ilka Hamann
Alfred Wegener Institute for Polar and Marine Research
Bremerhaven, Germany

Dr. Luca Placidi
Department of Structural and Geotechnical Engineering
"Sapienza" University of Rome, Italy

Dr. Thomas Zwinger
CSC - IT Center for Science
Espoo, Finland
 

Research areas

Dome Fuji, Antarctica77°19'S, 39°42'E
Greenland ice sheet~ 60-82°N, 20-70°W
Ushkovsky volcano, Kamchatka      56°04'N, 160°28'E

Publications

Seddik, H., R. Greve, T. Zwinger and L. Placidi. 2011.
A full Stokes ice flow model for the vicinity of Dome Fuji, Antarctica, with induced anisotropy and fabric evolution.
The Cryosphere 5 (2), 495-508. DOI: 10.5194/tc-5-495-2011.

Placidi, L., R. Greve, H. Seddik and S. H. Faria. 2010.
Continuum-mechanical, Anisotropic Flow model for polar ice masses, based on an anisotropic Flow Enhancement factor.
Cont. Mech. Thermodyn. 22 (3), 221-237. DOI: 10.1007/s00161-009-0126-0.

Greve, R. and S. Sugiyama. 2009.
Decay of the Greenland Ice Sheet due to surface-meltwater-induced acceleration of basal sliding.
ArXiv E-Prints, arXiv:0905.2027, URL http://arxiv.org/abs/0905.2027.

Greve, R., L. Placidi and H. Seddik. 2009.
A continuum-mechanical model for the flow of anisotropic polar ice.
Low Temp. Sci. 68 (Suppl.), 137-148. URL http://hdl.handle.net/2115/45440.

Seddik, H. 2008.
A full-Stokes finite-element model for the vicinity of Dome Fuji with flow-induced anisotropy and fabric evolution.
Doctoral thesis, Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan.
URL http://hdl.handle.net/2115/34136.

Seddik, H., R. Greve, L. Placidi, I. Hamann and O. Gagliardini. 2008.
Application of a continuum-mechanical model for the flow of anisotropic polar ice to the EDML core, Antarctica.
J. Glaciol. 54 (187), 631-642. DOI: 10.3189/002214308786570755.

Greve, R. and S. Otsu. 2007.
The effect of the north-east ice stream on the Greenland ice sheet in changing climates.
The Cryosphere Discuss. 1 (1), 41-76. DOI: 10.5194/tcd-1-41-2007.

Otsu, S. 2007.
The effect of the North-East Greenland Ice Stream (NEGIS) on the Greenland ice sheet in changing climates.
Master thesis, Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan.
URL http://hdl.handle.net/2115/28752.

Zwinger, T., R. Greve, O. Gagliardini, T. Shiraiwa and M. Lyly. 2007.
A full Stokes-flow thermo-mechanical model for firn and ice applied to the Gorshkov crater glacier, Kamchatka.
Ann. Glaciol. 45, 29-37. DOI: 10.3189/172756407782282543.
 

Research funding organisation

Japan Society for the Promotion of Science (JSPS).

Project type: Grant-in-Aid for Scientific Research (B).
Project number: 18340135.
Funding period: April 2006 - March 2009.
 

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Last modified: 2011-06-08