This polygon shapefile shows the approximate extent of marine areas in the Arctic covered by permanent polar ice. The data originated from the Canadian Ice Service and was used in the 1:6,000,000 National Atlas of Canada Reference Map Series. It is represented by polygons showing the average minimum ice limit over a 30 year period, 1969-1999. This layer is part of the 1997-2014 edition of the National Atlas of the United States.The North American Atlas data are intended for geographic display and analysis at the national and continental level. The data should be displayed and analyzed at scales appropriate for 1:10,000,000-scale data. No responsibility is assumed by Natural Resources Canada, Instituto Nacional de Estadística Geografía e Informática, or the U.S. Geological Survey in the use of these data.