The past decades of observations have shown sustained changes in the Arctic Ocean and the Arctic sea ice cover. Since the beginning of satellite observations in 1979, the Arctic sea ice extent has declined throughout all seasons, with the largest reduction occurring in summer. Furthermore, the Arctic sea ice cover is now thinner, weaker and drifts faster. The ocean shows an increase in the Arctic freshwater storage and warmer inflows from the Atlantic and Pacific Oceans. Coastal runoff from Siberia and Greenland has also increased. As the global surface temperature rises, the Arctic Ocean is speculated to become seasonally ice-free in the 21st century, which prompts us to revisit our perceptions of the Arctic system as a whole. What could the Arctic look like in the future? How are the present changes in the Arctic going to affect the lower latitudes? What aspects of the changing Arctic should future observations and modeling programs address? The session invites observation- and modeling-based submissions on past, present and future states of the Arctic, on the mutual interaction between ocean, atmosphere and sea ice, and links to global processes. The session promotes results from current Arctic programs and encourages discussions on future plans for Arctic Ocean modeling and measurement strategies.