Funds are provided to use output fields from runs of the National Center for Atmospheric Research Community Climate System Model, version 3 (CCSM3) to understand the mechanisms responsible for initiating, transitioning through, and recovering from large-scale Arctic sea ice anomalies. A particular focus is placed on events in which the late summer sea ice extent episodically decreases to levels drastically below those ever observed in the era recorded by multichannel satellite data and then recovers. The principal mechanisms responsible for development of and the recovery from these anomalous low sea ice events in the model runs will be identified. The proposed work plan consists of three tasks. The study will: o evaluate simulated atmospheric and oceanic conditions that lead to significant low-ice events and subsequent recovery to normal late season ice extent, as well as provide a detailed time series of the ice mass and heat budgets during these phases, o use an offline detailed sea ice model to further examine the relative roles of dynamic versus thermodynamic processes, oceanic versus atmospheric forcing, and winter preconditioning versus summer mechanisms leading to the simulated anomalies, and o examine coupled model experiments under anthropogenic forcing scenarios to study how the mechanisms associated with anomalies in the control simulations are altered and interpret the resultant sea ice evolution in light of model strengths and deficiencies that will be identified in the first two tasks.
