THREE-DIMENSIONAL DISCRETE ELEMENT MODELING OF FIRST-YEAR SEA ICE RIDGES

A three-dimensional discrete element model has been developed to investigate the evolution of particular aspects of pressure ridges in thin, first-year, sea ice. The primary goal of this work is to test one facet of recent theoretical advances in the representation of sea ice thickness in Earth System Models that advocates for the introduction of macro-porosity, R, to the state space of basin-scale sea ice models. Macro-porosity is caused by cavities between fractured sea ice blocks created during the formation of ridges during convergence of ice floes in the Southern and Arctic Oceans. Previously, sea ice thickness in basin-scale sea ice models has been represented by a real thickness distribution, g(h), but new mathematical derivations suggest that this should be replaced in predictive models with a bivariate distribution, g(h, R). In this thesis, a discrete element model of sea ice is described and then used to investigate the evolution of R in three-dimensional ridges. Changes in R over time are extremely difficult to measure in the Arctic, and therefore this research bridges observational constraints and theoretical assumptions. The final results suggest that, within the constraints of the given discrete element model, a more sudden change in macro-porosity occurs at the initial creation of a ridge than current theory suggests, but thereafter evolution of macro-porosity follows a path similar to what a Coulombic friction model predicts.http://archive.org/details/threedimensional1094562801Outstanding ThesisLieutenant, United States NavyApproved for public release; distribution is unlimited