Having meanwhile lost almost half of its summer sea ice extent, the Arctic Ocean seems to continue its transition towards a seasonally ice-free ocean which some climate models predict to occur in about 30 years. The past years showed a somewhat increased amount of young multiyear ice while the amount of thick multiyear ice has continued to decline. Furthermore extraordinarily freshening of the upper ocean and very warm inflow from the Atlantic and Pacific oceans occurred. While the coincidence of these evolutions raises the question of interactions or common causes they are difficult to evaluate because of our incomplete understanding of the polar climate components and our limited ability to model them. Significant effects of a shrinking sea ice cover on global climate, and marine biology are expected.
Possible reasons for current changes are seen in large-scale circulation changes with partly unclear connection to the ongoing global warming. The efforts of the International Polar Year 2007-2008 and other international programmes have enhanced the data flow from ice and ocean observations and contributed to improving modeling abilities from local to regional and global scales. The models are also progressing through increased model resolution and improved model physics. Also, increasing effort is invested in gaining more knowledge of the physical and biogeochemical properties of sea ice, exploring poorly understood sea ice processes, and forecasting future changes of the sea ice cover.

All these advance our understanding of the Arctic and the Antarctic system. We encourage presentations on observed and simulated changes in the Arctic and Antarctic sea ice, on snow and sea ice thermodynamics and dynamics, sea ice biological and chemical processes, as well as the ocean, and atmosphere, on their mutual interaction and on the interaction with the global processes. Discussion of future scenarios of the Arctic and Antarctic system is welcome.