CONICET | Buscador de Institutos y Recursos Humanos

Ice crystals shear easily along the slip systems in their basal planes, while shear on the other slip systems are nearly two orders of magnitude harder. The bulk response of a glacier to shear (flow) can be significantly altered if the crystals exhibit a preferred orientation, or fabric, as see in many glaciers and ice sheets. Further, a positive feedback mechanism exists between fabric development and ice deformation which may allow the vertical variation in fabric to retain information about the climate history. We explore both the evolution of a particular climatic event as well as the bulk fabric evolution through time within Taylor Dome, East Antarctica, where an ice core was drilled to bedrock in 1991-1994. We model bulk fabric evolution driven by a stress history derived from the geometry, temperature and depth-age relation and study the sensitivity of the results to initialization of near-surface fabric and the results are validated by thin-section fabric data. A climatic event can induce a subtle change in the near surface fabric. We model the evolution of this subtle change through time under different stress scenarios. The model is based on that developed by Thorsteinsson (2002), which is based on the homogeneous stress assumption and includes crystal growth, polygonization, migration recrystallization, and the influence of neighboring crystals on each crystals rotation. Our model successfully captures the large-scale fabric variations observed in the Taylor Dome record. We find that the influence of neighboring crystals have negligible effects over millennial time scales, and small effects over longer ice-sheet time scales. Furthermore, our model suggests that the fabric-climate feedback mechanism enhances small climate-induced variations in fabric and results in crystal size variations over time.