Increasing evidence underlines the importance of understanding the natural atmosphere and ocean variability, including the ocean-atmosphere-ice interaction, at decadal to millennial time scales. It remains a matter of debate, to which extent solar and volcanic forcing or internal ocean oscillations account for these climatic shifts which, among others, involve significant changes in Arctic sea-ice conditions, ocean and atmospheric temperature, storminess, and precipitation patterns around the world. Outlet-glacier dynamics may also be influenced due to subsurface ocean warming affecting glacier melting. The main objective of this session is to focus on the origin and mechanisms involved in decadal- to millennial-scale ocean and atmospheric variability. The session is co-organised with the COST-Action programme ‘INTIMATE’.