for Arctic Observing Summit (AOS) 2018 see http://www.arcticobservingsummit.org The Arctic Observing Viewer (AOV): Visualization, Data Discovery, Strategic Assessment, and Decision Support for Arctic Observing Ari Kassin1, Ryan Cody1, William Manley2, Allison Gaylord3, Sandra Villarreal1, Mauricio Barba1, Stephen Escarzaga1, Ted Habermann5, Naomi Whitty6, and Craig E. Tweedie1 1 Biological Sciences, University of Texas at El Paso; 2 INSTAAR, Univ. of Colorado; 3 Nuna Technologies; 4 CH2M Hill Polar Services; 5 The HDF Group; 6 Polar Field Services Inc. To better assess progress in Arctic Observing made by SAON, US AON, NSF AON, and related initiatives, an updated version of the Arctic Observing Viewer (AOV; http://ArcticObservingViewer.org) has been released. This web mapping application and information system conveys the who, what, where, and when of "data collection sites" – the precise locations of monitoring assets, observing platforms, and wherever repeat marine or terrestrial measurements have been taken. Over 13,000 sites across the circumarctic are documented including a range of boreholes, towers, ship tracks, buoys, sampling stations, sensor networks, vegetation plots, stream gauges, ice cores, observatories, and more. Contributing partners are the US NSF, NOAA, the NSF Arctic Data Center, ADIwg, AOOS, CAFF, GTN-P, IASOA, INTERACT, Isaaffik, NASA ABoVE, NSIDC, and USGS, among others, covering 22 initiatives and networks. Users can visualize, navigate, select, search, draw, print, view details, and follow links to obtain a comprehensive perspective of monitoring activities. We continue to develop, populate, and enhance AOV. Recent updates include: a vastly improved Search tool with free text queries, autocomplete, and filters; faster performance; new Observatories and Stations map layers; a new public-facing web service; additional documentation for interoperability of ISO site-level metadata; and more. AOV is founded on principles of interoperability, such that agencies and organizations can use the AOV Viewer and web services for their own purposes. In this way, AOV complements other distributed yet interoperable cyber resources and helps science planners, funding agencies, investigators, data specialists, and others to: assess status, identify overlap, fill gaps, optimize sampling design, refine network performance, clarify directions, access data, coordinate logistics, and collaborate to meet Arctic Observing goals.