Project activities during the first reporting period have focused heavily on model development, evaluation of model performance and analysis of shortcomings, and compilation of an extensive set of observations ranging from local in-situ process level to satellite observations and from targeted polar campaigns to integrated long term observations. CRiceS teams have developed methodologies to maximize utilization of observations as constraints for simulation ensembles, evaluation and validation data, or as a source of semi-empirical parameterizations or data-driven simulation approaches. These approaches have been developed for each project Core Theme: heat, mass and momentum exchanges (CT1), aerosols & clouds (CT2) and biogeochemical cycles/greenhouse gas exchanges (CT3), and CT4 which integrates our interdisciplinary understanding of ocean-ice-snow-atmosphere processes that operate together within the coupled OIA system. During the first 18 months, CRiceS has advanced the understanding of the physical, biological and chemical processes in polar and global systems, in atmosphere, sea ice and ocean. Atmospheric models have been expanded with new formulations of aerosol and cloud processes and chemical mechanisms. Biogeochemistry and related fluxes have been incorporated in several sea ice models, and the physical descriptions of sea ice itself have been revised and their limitations analysed.