1. Introduction.(Arctic Observing Network: Toward a U.S. Contribution to Pan-Arctic Observing)

The Arctic environment is changing. The changes are large, rapid and system-wide. They have few equals elsewhere on Earth, and some are occurring at greater rates than predicted by computer models. Arctic Change has regional and global implications, and continued changes will have significant Arctic and worldwide environmental and societal consequences.

Nothing illustrates the scale of Arctic Change, and its regional and global implications, better than the dramatic recession of the Arctic sea ice cover in summer 2007 (Figure 1). That this should have occurred early in International Polar Year (IPY) 2007-2009 exemplifies the global importance of the Arctic and the need for continued and greater vigilance via enhanced, coordinated and sustained observing infrastructure, i.e., AON.

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The magnitude and rate of the system-wide changes in the Arctic are such that there is broad consensus that enhanced, coordinated and sustained observing is vital. Current observing capabilities are not adequate to support the synthesis and modeling that are essential for better understanding of the regional and global causes and consequences of Arctic Change. Without improved observing capabilities and understanding of Arctic Change, regional and global society's ability to anticipate, predict and develop effective adaptive responses to future changes will be severely limited. Improved observing capabilities will be needed for the assessment of the effectiveness of efforts to mitigate the effects of global change and regional feedbacks in the Arctic.

This report focuses on US Federal observing activities in the Arctic as they relate to the development of AON to advance the goals of SEARCH. The report also describes many sub-Arctic observing activities. The Arctic is not isolated from the rest of the world, and AON must include the sub-Arctic ...