Laboratory determination of crevasse fracture criterion using crack arrest fracture toughness
Abstract
Crevasse propagation and iceberg calving predictions within ice sheet models conflict with direct observations of crevasse processes. Current ice sheet models assume that a crevasse will propagate until it reaches a depth where the critical stress intensity factor at the crack tip is less than that of crack initiation, however, this is likely an oversimplification. In situ measurements of crevasse crack tip stresses are difficult to obtain, requiring the use of laboratory measurements such as tensile strength, modulus of elasticity, and critical stress intensity factor when modeling likely crevasse properties. In addition to these properties, a more robust model should account for the crack arrest fracture toughness, which can predict how well a material can stop an already propagating crack. Here, we present data from laboratory-manufactured samples of polycrystalline ice with similar plane-strain fracture toughness values to that of meteoric ice. These samples were created using a radial freezing technique with a reproducible grain size distribution of 0.93 mm ± 0.14 mm analyzed by cross-polarized light. Specimens were notched and brought to failure via a short-rod fracture toughness test at controlled temperatures and a constant displacement rate in a commercial mechanical testing apparatus with an environmental chamber. Thus far, the results from these tests agree with short-rod fracture toughness data collected from ice cores at the Filchner-Ronne Ice Shelf in Antarctica, demonstrating a stick-slip fracture behavior. Initial results show the crack arrest fracture toughness of laboratory-manufactured polycrystalline ice is approximately 75% of the critical stress intensity factor. While the current crevasse models already overestimate crevasse depth, using the crack arrest fracture toughness determined in this study would increase modeled crevasse depth, indicating more analysis is required. It is expected that further data collected from this study will help constrain ice sheet models to more accurately determine crevasse penetration depth and improve iceberg calving predictions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMC022.0018A
- Keywords:
-
- 0728 Ice shelves;
- CRYOSPHERE;
- 0774 Dynamics;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE