The International Study of Arctic Change (ISAC) is an arctic environmental change program initiated in 2003 by the IASC and the Arctic Ocean Sciences Board. ISAC's vision is one of timely, relevant, and accessible scientific information for responding to rapid arctic change. ISAC is an open ended, international, interdisciplinary arctic environmental change program. To succeed ISAC requires observation and tracking of arctic changes, understanding their nature and causes, and the feedbacks and connections among them. ISAC encompasses pan-Arctic, system-scale, multidisciplinary observations, synthesis and modeling to provide an integrated understanding of arctic change and projections of future change. The ISAC Science Plan provides a vision for integrating research among diverse fields and varied users and stakeholders. ISAC is motivated by environmental changes that are already large enough to affect life in the Arctic. Future system states are uncertain and the lack of predictability hinders efforts to develop strategies for adapting to and managing a changing Arctic.