Sea Ice Dispersion using Lagrangian Dynamics: a dynamical systems study

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Observations show that the Arctic is experiencing drastic changes under climate change. Increased drift velocities of sea ice are found in regions with reduced multiyear sea ice coverage, with the thinner and mechanically weaker first year ice showing a higher responsiveness to the wind forcing. A better understanding of sea ice dynamics is thus needed in order to predict its evolution and its variability under climate change. In particular, at local scales the dynamical evolution of sea ice is determined by its strain and deformation, which in turn are responsible for its dynamical evolution and for example for its fracturing, and for its dispersion. In this study we propose to analyze the kinematics of sea ice studying its Finite Scale Lyapunov Exponents (FSLEs) from observations from buoys deployed on sea ice. Statistics of the displacements of the particles, such as the probability density functions and the frequency spectra, will first be analyzed. The FSLEs can be used, for example, to characterize dynamics that possess a multi-scale nature, such as indeed sea ice. The fact that they have a dimension of the inverse of a time indicates that they can be used as an indicator of predictability of the flow: its inverse gives a typical time-scale for the separation of nearby particles and thus for the deformation of the sea ice. FSLEs are also directly connected to the horizontal dispersion of particles (buoys), indicating if the separation of the buoys in time is exponential (chaotic), linear (diffusive) or if it follows an anomalous diffusion. The repetition of the calculation for different regions and for different years will hopefully highlight a dependence of the dynamical features considered to different climate conditions.