This line shapefile represents the extent of glaciers during the late Wisconsin glaciation (also known as the Last Glacial Maximum, about 20,000 years ago). Pleistocene glaciers once covered >1,200,000 km2, from the continental shelf bordering the North Pacific to the northern foothills of the Brooks Range. Late Wisconsin glaciers occupied 727,800 km2 -- nearly ten times the area of modern glaciers, but only 48% of the state. Alaska's glaciers expanded more than 20 times during the last 3 million years in response to cold and snowy conditions. During the late Wisconsin glaciation, when sea level fell approximately 125 m (approx. 400 ft), the Bering Land Bridge was exposed as a broad tundra plain, and much of the state escaped glaciation due to a cold but dry climate. Deposition and erosion by glaciers in the recent geologic past have greatly influenced Alaska's landscapes and ecosystems. This report is an update of the Alaska PalaeoGlacier Atlas. It includes information published since 2002 and is based on a more detailed map scale. In addition to the all-time maximum extent of former glaciers and the late Wisconsinan extent, this update includes the mapped limit for the penultimate glaciation, which generally occurred during the early Wisconsinan. The update also includes a compilation of cosmogenic exposure ages linked to the geospatial database. The Alaska PalaeoGlacier Atlas is a geospatial summary of Pleistocene glaciation across Alaska. Our goal is a comprehensive and consistent overview of former glacier limits across Alaska. Our hope is to facilitate outreach, education, and interdisciplinary research in the fields of geology, geography, biology, and natural history. Coastal boundary aligned with imagery, no gaps in polygon, no topological errors, aggregate and % figures verified This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.
