Abstract
Monitoring drift ice in the Arctic and Antarctic regions directly and by remote sensing is important for the study of climate, but a unified modeling framework is lacking. Hence, interpretation of the data, as well as the decision of what to measure, represent a challenge for different fields of science. To address this point, we analyzed, using statistical physics tools, satellite images of sea ice from four different locations in both the northern and southern hemispheres, and measured the size and the elongation of ice floes (floating pieces of ice). We find that (i) floe size follows a distribution that can be characterized with good approximation by a single length scale , which we discuss in the framework of stochastic fragmentation models, and (ii) the deviation of their shape from circularity is reproduced with remarkable precision by a geometric model of coalescence by freezing, based on random Voronoi tessellations, with a single free parameter expressing the shape disorder. Although the physical interpretations remain open, this advocates the parameters and as two independent indicators of the environment in the polar regions, which are easily accessible by remote sensing.
Highlights
Monitoring drift ice in the Arctic and Antarctic regions directly and by remote sensing is important for the study of climate, but a unified modeling framework is lacking
We find that (i) floe size follows a distribution that can be characterized with good approximation by a single length scale δl, which we discuss in the framework of stochastic fragmentation models, and (ii) the deviation of their shape from circularity is reproduced with remarkable precision by a geometric model of coalescence by freezing, based on random Voronoi tessellations, with a single free parameter σ expressing the shape disorder
We take an empirical approach to the question of defining useful observables regarding sea-ice morphological properties, and analyze data obtained from satellite images of sea ice detached from the shoreline, called drift ice, focusing on the size and shape of the individual floes that drift ice is composed of
Summary
Marco Gherardi1,2 & Marco Cosentino Lagomarsino[3,4] received: 22 October 2014 accepted: 17 March 2015 Published: 27 May 2015. We point out that all available models of crack propagation in brittle solids yield the same results in terms of scaling, and while the single length scale we uncover is an effective measure of the state of fragmented ice, its physical interpretation is elusive and needs to be probed by direct experiments These results lead to the conclusion that floe size alone cannot be a fully informative measurement of sea-ice properties. Such a measure can in principle distinguish between isotropic and non-isotropic physical processes (e.g., lateral melting versus stress failure[22]) Another important feature of elongation is that it is independent of size, as we demonstrate directly with empirical data of sea ice. The distribution of floe elongations measured from satellite data leads us to propose a one-parameter model, describing the shapes of ice floes as the Voronoi cells of randomly-placed seeds.
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