Discrete-element models of sea ice dynamics and fracture

At geophysical scales, continuum models provide established and computationally efficient tools for simulating sea ice dynamics and thermodynamics. In recent years, rapidly increasing computational power and availability of high-resolution (esp. remote-sensing) data have contributed to a revival of discrete-element methods (DEM), enabling the analysis of sea ice at smaller spatial and temporal scales. Treating sea ice as a collection of individual, interacting floes, and thus recognizing it as an example of a granular material, opens a wide range of new tools and analysis possibilities for sea ice research. Bonded-particle DEM models enable to simulate brittle fragmentation of sea ice – a process that, in spite of substantial progress in recent years, still poses problems for continuum models. Moreover, there is growing evidence that the size distribution of sea ice floes has a substantial influence on a wide range of processes in the upper ocean, lower atmosphere and within sea ice itself, and it is in turn shaped by those processes. By directly taking into account fragmentation (i.e., floe formation) and dynamics of individual floes, DEMs provide tools to better understand complex interactions between sea ice, ocean and atmosphere acting at the floe-level.

In this talk, I will present and discuss selected examples of the application of DEM models to sea ice dynamics and fragmentation problems. The examples will include: wind- and current-induced drift of fragmented (``granular’’) sea ice, and the influence of ice concentration and floe-size distribution on the sea ice response to forcing; jamming phase transition under compressive and shear strain, and force transmission in ice subject to different strain fields; sea ice breaking by waves analyzed with a coupled DEM–hydrodynamic model. Unsolved problems and challenges (both computational and theoretical) related to the application of DEMs to sea ice will be presented as well.

Most results presented in this talk were obtained with a Discrete-Element bonded-particle Sea Ice model DESIgn, implemented as a toolbox for the open-source numerical library LIGGGHTS (http://www.cfdem.com/). The code and documentation of DESIgn are freely available at http://herman.ocean.ug.edu.pl/LIGGGHTSseaice.html.