On the problem of sea ice mechanics

In the context of short-tenn sea ice forecasting, the model should capture as many of the synoptic features and as much of their variability. as possible. We are interested in the meso-scale properties and processes, i.e. thickness, consolidation, compactness, smoothness, accumulation of ridges, formation of leads and ice edge, drift and displacement, etc. Modelling and forecasting of synoptic ice formation are of interest to shipping as it affects route planning and the operation of icebreakers. With a view to conventional ice charting, the forecast problem might read: Given today 's ice chart, what will tomorrow 's ice chart look like? The model has to return meso-scale features, while essential smaller-scale mechanisms have to be parameterised. The problem in a meso-scale model is to adequately take into account the governing fine-scale mechanisms. Pack ice is a crushable fragmented aggregate, characterized by point-like contacts and stress trajectories. In compressible loading, even local traction forces, causing brittle failure, may be induced. The localization of stress and strain is a considerable complication! By way of localization, critical phenomena at singular points, affect the entire structure. Meaningful characteristics are integrity, state of damage (flaws, cracks). fragmentation and skeletal structure (fabric of fragments, strength of the structure). Structural properties and their evolution dun·ng the material history could be represented by suitably chosen internal variables. To reflect the state of degradation, fragmentation, consolidation, etc., special concepts are required for the damage mechanics of fracturing pieces and fragmented aggregates. Using such a vehicle, the meso-scale mechanics of sea ice could be accommodated in a continuum mechanics model. More elements have been worked out in plasticity.