On modeling sea-ice fracture and flow in numerical investigations of climate

Abstract

Sea ice on the large scale is characterized by leads and ridges that typically have a given orientation. Because of various flaws, we would expect that the ice will form oriented leads and ice-thickness characteristics that control the heat and moisture fluxes into the atmosphere. Prediction of these oriented leads, ridges and slip lines is relevant to understanding the role of ice mechanics in global climate change as they can play a significant role in the ice-thickness distribution.In this paper we develop a model for the dynamical treatment of leads and oriented flaws in large-scale sea-ice models. Two particular isotropic realizations of this model relevant to climate studies are examined: (a) an isotropic composite with oriented leads in all directions imbedded in thick ice, and (b) a simple "strain hardening" isotropic model where only oriented leads having the potential to open rapidly are allowed. Under applied stress both models yield preferential deformation along a symmetric pair of intersecting leads or ridges with the intersection angles dependent on the confinement stress. The "uniform-orientation" model results in a yield curve that approximates a sine lens, while the "strain hardening" model has a teardrop-like yield curve. How the resulting fracture-based yield curves and non-normal flow rules may be cast in a form usable in numerical investigations of climate is discussed.