Sea Ice Cover Deformation on the Local Scale and Mesoscale and Its Relationship to Atmosphere-Ocean Processes

Abstract

This thesis is concerned with the study of sea ice cover deformation caused by the processes in the atmosphere and ocean. Only a modest number of studies has addressed the cross-scale analysis of the ice deformation. The aim of the present research has two foci: to investigate the variability of ice deformations and identify mechanisms responsible for their generation, and to explore the relationships of the ice deformation in the range of spatial scales. Two types of ice, the multi-year pack ice in the central Arctic and the seasonal ice in the northern Baltic Sea, are studied. The research includes a field experiment, observation analysis and modelling.

Stresses in the ice generated by non-uniform drift of ice, ocean waves, and ice deformation due to variations in the ambient air temperature are considered. To separate thermal and motion induced deformation on the floe scale a thermo-mechanical non-linear viscous-elastic model has been developed. The results from these simulations are compared with the observations from the field experiment. To study the aggregate behaviour of the ice cover the mesoscale deformations are analysed along with the local ice strain. The continuum anisotropic and granular ice models are employed to simulate the highly inhomogeneous spatial structure of the deformation fields observed. The wave emission due to ice failure is also investigated. A comparison of field observations and laboratory tests in an ice tank and asymptotic analysis allow us to identify mechanisms of the wave emission at frequencies between 0.2 Hz and 1.0 Hz. The scaling formalism for the ice deformation and stress is suggested.

The results of the data analysis and modelling have converged into a coherent scheme describing the spatial and temporal variability of the sea ice cover deformation from the local scale through the single floe scale to the mesoscale.