Large-scale atmospheric circulation modes affecting polar variability (Invited Presentation)

Polar variability and change is substantially influenced by a number of large-scale atmospheric circulation modes such as, for example, the North Atlantic Oscillation (or its hemispheric counterpart the Arctic Oscillation) and the Pacific Decadal Oscillation. In this presentation I will review our current understanding of these modes, both as seen in the instrumental record, and in global climate models with and without significant anthropogenic influence. Most of the information we have on these modes, and their change under global warming, is based on classical diagnostic tools (such as linear principal component analysis). However, more modern diagnostic techniques (such as nonlinear principal component analysis) are showing us large-scale variability structures that are much richer in space and time than previously thought. I will also review this new information - in particular with respect to interactions with the polar regions.