Star patterns on lake ice
Star patterns, reminiscent of a wide range of diffusively controlled growth forms from snowflakes to Saffman-Taylor fingers, are ubiquitous features of ice-covered lakes. Despite the commonality and beauty of these "lake stars," the underlying physical processes that produce them have not been explained in a coherent theoretical framework. Here we describe a simple mathematical model that captures the principal features of lake-star formation; radial fingers of (relatively warm) water-rich regions grow from a central source and evolve through a competition between thermal and porous media flow effects in a saturated snow layer covering the lake. The number of star arms emerges from a stability analysis of this competition and the qualitative features of this meter-scale natural phenomenon are captured in laboratory experiments.
Additional Information© 2007 American Physical Society. Received 14 February 2007; published 18 June 2007. We thank K. Bradley and J. A. Whitehead for laboratory and facilities support and D. H. Rothman for helpful comments. This research, which began at the Geophysical Fluid Dynamics summer program at the Woods Hole Oceanographic Institution, was partially funded by National Science Foundation (NSF) Grant No. OCE0325296, NSF Grant No. OPP0440841 (J.S.W.), and Department of Energy Grant No. DE-FG02-05ER15741 (J.S.W.). V. C. T. acknowledges financial support from NSF.
Published - TsaiWettlaufer_PRE2007.pdf