Effective rheology across the fragmentation transition for sea ice and ice shelves

• Published in: Geophysical Research Letters
• Main Authors: Åström, J.A., Benn, D.I.
• Other Authors: NERC, University of St Andrews. School of Geography & Sustainable Development, University of St Andrews. Bell-Edwards Geographic Data Institute
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Ice shelves; Sea ice; Modelling; G Geography (General); DAS; SDG 13 - Climate Action; G1; Antarctic; Arctic; Arctic Ocean; Antarc*; Ice Sheet; Ice Shelves
• Online Access: http://hdl.handle.net/10023/19967; https://doi.org/10.1029/2019GL084896

Funding was provided by the NERC grant NE/P011365/1 Calving Laws for Ice Sheet Models CALISMO. Data files for the plots are found at: https://doi.org/10.5285/76D7D3CA-7B83-4BB0-AAE5-A8E92C7DA5B0 Sea ice and ice shelves can be described by a viscoelastic rheology that is approximately linear elastic and brittle at high strain rates, and viscously shear‐thinning at low strain rates. Brittle ice easily fractures under compressive shear and forms shear bands as the material undergoes a transition to a fragmented, granular state. This transition plays a central role in the mechanical behaviour at large scales of sea‐ice in the Arctic Ocean or Antarctic ice shelves. Here we demonstrate that the fragmentation transition is characterized by an essentially discontinuous drop of 3‐5 orders of magnitude in effective viscosity and stress‐relaxation time. Beyond the fragmentation transition, grinding in shear zones further reduces both effective viscosity and shear stiffness, but with an essentially constant relaxation time of ∼10second. These results are relevant for ice‐rheology implementation in large‐scale climate‐related models of sea ice and thin ice shelves. Publisher PDF Peer reviewed