气候变化领域集成服务门户(CCPortal): Non-normal flow rules affect fracture angles in sea ice viscous-plastic rheologies

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DOI	10.5194/tc-15-2873-2021
	Non-normal flow rules affect fracture angles in sea ice viscous-plastic rheologies
	Ringeisen D.; Tremblay L.B.; Losch M.
发表日期	2021
ISSN	19940416
起始页码	2873
结束页码	2888
卷号	15 期号:6
英文摘要	The standard viscous-plastic (VP) sea ice model with an elliptical yield curve and a normal flow rule has at least two issues. First, it does not simulate fracture angles below 30 in uni-axial compression, in contrast with observations of linear kinematic features (LKFs) in the Arctic Ocean. Second, there is a tight, but unphysical, coupling between the fracture angle, post-fracture deformation, and the shape of the yield curve. This tight coupling was identified as the reason for the overestimation of fracture angles. In this paper, these issues are addressed by removing the normality constraint on the flow rule in the standard VP model. The new rheology is tested in numerical uni-axial loading tests. To this end, an elliptical plastic potential - which defines the post-fracture deformations, or flow rule - is introduced independently of the elliptical yield curve. As a consequence, the post-fracture deformation is decoupled from the mechanical strength properties of the ice. We adapt Roscoe's angle theory, which is based on observations of granular materials, to the context of sea ice modeling. In this framework, the fracture angles depend on both yield curve and plastic potential parameters. This new formulation predicts accurately the results of the numerical experiments with a root-mean-square error below 1.3. The new rheology allows for angles of fracture smaller than 30 in uni-axial compression. For instance, a plastic potential with an ellipse aspect ratio smaller than 2 (i.e., the default value in the standard viscous-plastic model) can lead to fracture angles as low as 22. Implementing an elliptical plastic potential in the standard VP sea ice model requires only small modifications to the standard VP rheology. The momentum equations with the modified rheology, however, are more difficult to solve numerically. The independent plastic potential solves the two issues with VP rheology addressed in this paper in uni-axial loading experiments, it allows for smaller fracture angles, which fall within the range of satellite observations, and it decouples the angle of fracture and the post-fracture deformation from the shape of the yield curve. The orientation of the post-fracture deformation along the fracture lines (convergence and divergence), however, is still controlled by the shape of the plastic potential and the location of the stress state on the yield curve. A non-elliptical plastic potential would be required to change the orientation of deformation and to match deformation statistics derived from satellite measurements. © Author(s) 2021.
英文关键词	Venustaconcha ellipsiformis
语种	英语
来源期刊	Cryosphere
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202412
作者单位	Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany; Marum - Center for Marine Environmental Sciences, Leobener Str. 8, Bremen, 28359, Germany; Department of Atmospheric and Oceanic Sciences, McGill University, Montréal, Canada
推荐引用方式 GB/T 7714	Ringeisen D.,Tremblay L.B.,Losch M.. Non-normal flow rules affect fracture angles in sea ice viscous-plastic rheologies[J],2021,15(6).
APA	Ringeisen D.,Tremblay L.B.,&Losch M..(2021).Non-normal flow rules affect fracture angles in sea ice viscous-plastic rheologies.Cryosphere,15(6).
MLA	Ringeisen D.,et al."Non-normal flow rules affect fracture angles in sea ice viscous-plastic rheologies".Cryosphere 15.6(2021).