Effect of shear rupture on aggregate scale formation in sea ice

Abstract

[1] A discrete element model is used to study shear rupture of sea ice under convergent wind stresses. The model includes compressive, tensile, and shear rupture of viscous elastic joints connecting floes that move under the action of the wind stresses. The adopted shear rupture is governed by Coulomb's criterion. The ice pack is a 400 km long square domain consisting of 4 km size floes. In the standard case with tensile strength 10 times smaller than the compressive strength, under uniaxial compression the failure regime is mainly shear rupture with the most probable scenario corresponding to that with the minimum failure work. The orientation of cracks delineating formed aggregates is bimodal with the peaks around the angles given by the wing crack theory determining diamond-shaped blocks. The ice block (floe aggregate) size decreases as the wind stress gradient increases since the elastic strain energy grows faster leading to a higher speed of crack propagation. As the tensile strength grows, shear rupture becomes harder to attain and compressive failure becomes equally important leading to elongation of blocks perpendicular to the compression direction and the blocks grow larger. In the standard case, as the wind stress confinement ratio increases the failure mode changes at a confinement ratio within 0.2-0.4, which corresponds to the analytical critical confinement ratio of 0.32. Below this value, the cracks are bimodal delineating diamond shape aggregates, while above this value failure becomes isotropic and is determined by small-scale stress anomalies due to irregularities in floe shape.

Impact of rheology on probabilistic forecasts of sea ice trajectories: application for search and rescue operations in the Arctic

“…Some, like neXtSIM, treat the sea ice as a continuous medium, but with different rheologies (e.g. Coon et al (1974) and Hibler III (1979) modelled sea ice as an elasto-plastic material; Hunke and Dukowicz (1997) as an elasto-visco-plastic material; and Dansereau (2016) as an Maxwell elasto-brittle material), and are suitable for high ice concentration (> 80 %), while others that treat the ice as a discrete medium (Hopkins et al, 2004;Wilchinsky et al, 2010;Herman, 2011;Rabatel et al, 2015) are more suitable for low ice concentration (< 80 %) such as within the marginal ice zone.…”

Atomistic simulations of friction at an ice-ice interface

“…Examples include fracture of the Arctic sea ice cover [2][3][4][5][6][7][8][9][10][11][12], brittle compressive failure during interactions between natural ice features and engineered structures [13,14], and tectonic activity of ice-encrusted bodies within the outer solar system [15][16][17][18][19][20][21][22][23][24]. For most of these systems, it is the friction of ice sliding upon itself that dominates the mechanics and heat generated at the interface.…”

Probabilistic forecast using a Lagrangian sea ice model: application for search and rescue operations

“…Some, like neXtSIM, treat the sea ice as a continuous medium, yet with different rheologies (e.g. visco-plastic (Coon et al, 1974;Hibler III, 1979), elasto-visco-plastic, (Hunke and Dukowicz, 1997), or Maxwell-elasto-brittle, (Dansereau, 2016)), are suitable 10 for high ice concentration (> 80%) while others, that treat the ice as a discrete medium (Hopkins et al, 2004;Wilchinsky et al, 2010;Herman, 2011;Rabatel et al, 2015), are more suitable for low ice concentration (< 80%) such as within the marginal ice zone.…”