Dynamical Processes in the Drifting Ice in the Arctic Ocean

Information about physical and mechanical processes in the ice based on instrumental observations on the drifting and land fast ice is presented. Methods of measurement of the parameters of ice oscillations and waves in Russian expeditions in the Arctic were used. Sea ice cover reacts to oscillations, surface and internal waves in atmosphere and in ocean. Force of interaction of sea ice generates large-scale effects of self-excited oscillations. Natural dynamical processes in the drifting ice floes (system ice-ice) reflect many forms of deformation and failure of the ice, observed at the interaction in the system ice-structure (lock-in or self- excited vibration). Especially it relates to the effects discussed in ISO 19906 2010 as a lock-in or self-excited vibration. The mechanics of interaction of a sea ice with icebergs also can be considered as analogue of interaction in the system ice-structure. Sea ice cover is a dynamical dissipative system of the geophysical level in which physical-mechanical processes of different scale and intensity occur simultaneously. Study of physical-mechanical properties of sea ice cover is based on consideration of ice as a material, and construction as a geophysical discrete medium which is under impact of atmosphere and ocean (1). Periodic horizontal shears on significant space of ice are registries; they are related to the class of self-excited oscillations. The mechanical processes in dynamic system ice-ice are very similar to processes in system ice-structure. Intermittent crushing of the contacts of ice floes, with regimes of resonance events, chaotic vibrations and impacts in ISO 19906 2010 (2) are revealed It follows a necessity of a complex investigation of the sea ice for solution of weather and climate tasks and ice technology interconnected with ice impact to offshore engineering structures. Scientific and applied problems of the sea ice are interconnected and are solved by experimental and theoretical methods. A structure of the sea ice cover is analyzed by using theories of elasticity, viscosity and plasticity. Thus general strategy of investigation was realized at natural experiments and monitoring of the mechanical state of land fast and drifting ice in the Arctic. As a rule, except for traditional measurements, two main tasks were set: — investigation of physical-mechanical processes of deformation and failure of ice to obtain data for development of forecast method of ice state and its failure in advance of several hours; — consideration of possibility in the future use of obtained data for solution of tasks of ice bearing capacity and evaluation of ice actions onto shores, bottom and structures of the Arctic shelf. The technology of monitoring ice state is based on interconnected tasks of ice mechanics, morphometry and geophysical processes, which occur under action of external forces from atmosphere and water. The inverse tasks allow using mechanical changes in ice and giving estimate of forces, which cause these changes. It makes a possibility of prediction of time and place of extreme ice phenomena, which is especially important during exploitation of the offshore structures and navigation in ice. Such approach allows to integrate applied and scientific tasks: evaluation of ice strength of local and meso scale, short-term forecast of sea ice compression, evaluation of ice loads on structures.