Simulating Arctic Ocean-Atmosphere-Ice Interactions with a Single Column Model Version of the Community Climate System Model

We present a single column model (SCM) version of the Community Climate System Model (CCSM), that includes the upper 20 meters of the ocean, the sea ice, and the atmosphere. The model is forced by incoming solar radiation at the top boundary, vertical heat and salt fluxes at the bottom boundary, horizontal advection of mass, heat and moisture in the atmosphere, horizontal fluxes of heat and salt in the ocean, the ice velocity relative to the upper ocean, and the shear and divergence of the sea ice velocity field. Experiments are performed at Lagrangian horizontal coordinates that move with the sea ice. Two sets of simulation experiments are performed to study how ice-albedo feedback and cloud-radiation feedback manifest themselves in a single annual cycle, and in a climate change scenario. In the first set of experiments, model initialization and forcing data are prescribed from data sets produced by the Surface Heat Budget of the Arctic Ocean (SHEBA) and the First ISCCP Regional Arctic Cloud Experiment (FIRE-ACE) projects. These SHEBA/FIRE-ACE data sets extend over time periods up to 1 year. In the second set of experiments, stochastic forcing is prescribed by sampling random processes with realistic climatological statistics. These randomly-forced experiments extend over time periods of many decades. Feedbacks are quantified by comparing pairs of experiments in which specific variables (e.g. surface albedo) are first allowed to interact freely as part of the coupled system, and then are prescribed as time series. The results indicate similarities and differences between the feedback mechanisms evaluated on short and long time scales.