The Arctic region and surrounding circumpolar region is the key area for the study of global change because the anthropogenic impact is projected to be the largest in this area due to the complicated feedback processes of the nature. A number of international and interdisciplinary research projects have been conducted for the studies on the atmosphere-ocean-land system under the auspice of the International Polar Year (IPY) Project. In order to understand the feedback processes occurring in the Arctic and to project the global warming in the future, we need to establish the intense observational network and to exchange the knowledge and information by combining the different scientific communities under the common interest of the Arctic. The objective of the session is to exchange our knowledge on the observational facts and to deepen our understanding on wide range of natural sciences related to the Arctic and the circumpolar region.