Author(s): Knut V. Hoyland
Linked Author(s): Knut Hoyland
Keywords: No Keywords
Abstract: Thermal aspects of model basin first-year ice ridges have been investigated theoretically and compared with existing model-basin experiments. The ridges were assumed to be characterized by some constant geometrical characteristics (the thickness of the consolidated layer, hc, the macro-porosity, η, the individual ice block thickness, hb, the keel depth, hk and width wk) and BY mechanical properties of respectively the consolidated layer and the unconsolidated part of the keel (the rubble). The smaller size in basins gives less oceanic flux and relatively more ice growth. Shorter consolidation time makes the initial phase (that is the effect of the initial conditions, in particular the initial ice temperature, Ti) more important and hc in basin-scale ice ridges is reported to be relatively thicker than in full-scale. This can be compensated for by lowering the potential for ice growth by increasing the initial ice temperature (Ti). However, it is important to cool the surface of the ridge after it has been created so that the consolidated layer forms on the top of the ridge, and not internally. The strength of the consolidated layer can be scaled by heating (as is often done with level ice), but it is difficult to simultaneously target both the surrounding level ice and the consolidated layer by heating. The latter is thicker and insulated below by the rubble and will become too cold and thus too strong. The rubble in model basin ridges is often reported to be substantially weaker than in full-scale ridges even with identical temperature during testing. This may simply be related to the fact that the initial stress state is proportional to the keel depth and automatically scales as such. However, the formation and strength of the freeze-bonds are also important and these are governed by thermodynamics. The freeze-bonds easily get weaker in model basin-scale and by a proper combination of initial conditions (Ti) and conditions during consolidation (∆t and Ti) the strength of mode basin rubble may be scaled according the desired scaling laws.
Year: 2010