Topics::sea-icesea-ice-dynamics Zotero
Rheology-based sea ice dynamics: From the fluid-like to the state-of-the-art solid-like brittle approach.
Abstract
The increasing interest in the climate in general and, in particular, in the role that Arctic processes play within it has led to an increasing demand for accurate predictions for sea ice motion. However, the problem of finding suitable equations to accurately describe the drift and deformation of the sea ice cover has challenged the sea ice dynamics community for many years. This thesis presents the developments in sea ice modeling research, from its origins to the current state focusing on models based on a continuum mechanics framework. To do so, we will first describe the relevant sea ice state parameters: sea ice velocity, sea ice thickness, sea ice concentration, internal sea ice stresses and sea ice properties like cohesion as well as the equations describing their time evolution. Special attention will be devoted to the formulation of the internal stress as function of the (rate of) deformation, i.e. the rheology. This relation changed from being absent, as the earliest models did not include internal stresses, via a simple linear relation, similar to the one found in a viscous fluid, to rheologies in which ice can exhibit different relations below and above a critical stress threshold given by a yield curve. The Mohr-Coulomb curve and elliptic yield curves will be discussed. Subcritical ice behavior is either elastic, viscous or a combination of the two. Supercritical ice deforms plastically. Discussed examples of such rheologies are the elastic-plastic (EP) and viscous-plastic (VP) rheologies. As a consequence of the need to stay within the yield curve, the viscosity and/or elasticity needs to change. It has been found that models are more capable of reproducing features in the sea ice if the processes happening at a lower scale than the model spatial resolution are parametrized. This has resulted in the development of the the Elasto-Brittle (EB), the Maxwell-Elasto- Brittle (MEB) and the Brittle-Bingham-Maxwell (BBM) rheologies. The latter is the current state-of-art model rheology successful in reproducing the multifractal nature of sea ice deformation in both space and time, i.e. the characteristic heterogeneity and intermittency.