Sustained high basal motion of the Greenland ice sheet revealed by borehole deformation

• Main Authors: Ryser, Claudia, Lüthi, Martin P, Andrews, Lauren C, Hoffman, Matthew J, Catania, Ginny A, Hawley, Robert L, Neumann, Thomas A, Kristensen, Steen S
• Format: Article in Journal/Newspaper
• Language: English
• Published: International Glaciological Society 2014
• Subjects: Institute of Geography; 910 Geography & travel; Greenland; Ice Sheet; Journal of Glaciology
• Online Access: https://www.zora.uzh.ch/id/eprint/101718/; https://www.zora.uzh.ch/id/eprint/101718/1/2014%20L%C3%BCthiM_s4%20.pdf; https://doi.org/10.5167/uzh-101718; https://doi.org/10.3189/2014JoG13J196

Ice deformation and basal motion characterize the dynamical behavior of the Greenland ice sheet (GrIS). We evaluate the contribution of basal motion from ice deformation measurements in boreholes drilled to the bed at two sites in the western marginal zone of the GrIS. We find a sustained high amount of basal motion contribution to surface velocity of 44–73% in winter, and up to 90% in summer. Measured ice deformation rates show an unexpected variation with depth that can be explained with the help of an ice-flow model as a consequence of stress transfer from slippery to sticky areas. This effect necessitates the use of high-order ice-flow models, not only in regions of fast-flowing ice streams but in all temperate-based areas of the GrIS. The agreement between modeled and measured deformation rates confirms that the recommended values of the temperature-dependent flow rate factor A are a good choice for ice-sheet models.