On Processes and Feedbacks Contributing to Arctic Amplification

Results from a hierarchy of numerical models, including those participating in the Coupled Model Intercomparison Project Phase 3 and 5 (CMIP3/5) and Regional Arctic Climate System Model (RASM), are analyzed to evaluate their representation of potentially critical physical processes and air-sea interactions of relevance to the long-term negative trend of the Arctic sea ice cover and regional amplification of climate warming. In particular, the flow across the Chukchi Sea, pathways of Pacific Water and oceanic forcing of sea ice and feedbacks to the atmosphere in the western Arctic are examined. We hypothesize that the northward advection of Pacific Water together with the excess oceanic heat that has accumulated below the subsurface mixed layer in the western Arctic Ocean due to diminishing sea ice cover and subsequent increased solar insulation are critical factors affecting sea ice growth in winter and melt the following year. We argue that a better understanding and an improved model representation of the regional ocean dynamics are needed to advance knowledge and improve prediction of the accelerated decline of sea ice cover and Arctic amplification of global warming.