NOTE: The data product titled U.S. National Ice Center Arctic and Antarctic Sea Ice Concentration and Climatologies in Gridded Format supersedes this product. It begins with charts from January 2003 and is updated weekly. The U.S. National Ice Center (NIC) is an inter-agency sea ice analysis and forecasting center comprised of the Department of Commerce/NOAA, the Department of Defense/U.S. Navy, and the Department of Homeland Security/U.S. Coast Guard components. Since 1972, NIC has produced Arctic and Antarctic sea ice charts. This data set is comprised of Arctic sea ice concentration climatology derived from the NIC weekly or biweekly operational ice-chart time series. The charts used in the climatology are from 1972 through 2007; and the monthly climatology products are median, maximum, minimum, first quartile, and third quartile concentrations, as well as frequency of occurrence of ice at any concentration for the entire period of record as well as for 10-year and 5-year periods. These climatologies and the charts from which they are derived are provided in the 25-km Equal-Area Scalable Earth Grid (EASE-Grid) binary (.bin) format. The climatologies are also available in ArcGIS geodatabases (.mdb), and GIF format browse files (.gif) are also provided. To view the browse files and compare climatological periods visually, choose Search Database under the Download Data tab.