Author(s): Robert S. Pritchard

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Keywords: No Keywords

Abstract: A plastic sea ice model is studied to determine the relationships between velocity and stress characteristics and observed lead patterns. The velocity and stress fields can independently be hyperbolic, parabolic, or elliptic at different locations depending on the local stress state. Leads intersect at different angles north of a structural arch formed across the Fram Strait, and appear to be aligned with characteristics. Homogeneous deformation of a field of ice floes is simulated for uniform diamond-shaped floes and a random distribution of circular floes. Simulated leads are not collinear with velocity characteristics, but open across the direction of maximum principal stretching. These disparate and apparently conflicting observations are brought into a unified theory by assuming that velocity characteristic directions do align with leads, but only if external forcing and boundary conditions induce a velocity discontinuity along the characteristic direction. Existence of a velocity characteristic is necessary, but not sufficient, for the model to describe a lead. Characteristics cannot exist if strength is zero, and then leads open across the direction of maximum principal stretching. Finally, some of the stretching states that can be simulated by this kinematic model must be assumed to be unattainable because closing in the direction of minimum principal stretching would require redistribution of ice floes by rafting or ridging, which is not described in the kinematic model.

DOI:

Year: 1992