Dataset: Accelerated Retreat of Coastal Glaciers in the Western Prince William Sound, Alaska
Description
Analyzing historical maps and Landsat imagery indicates that coastal glaciers in the western Prince William Sound (PWS) have retreated since the end of the Little Ice Age, exhibiting accelerated retreat after the mid-2000s. A multi-temporal inventory of 43 glaciers was developed using historical field observations, topographic maps, and Landsat imagery. Area and length measurements are derived from digitized outlines, and center lines are derived from a semi-automatic, GIS-based algorithm. Land-based glaciers retreated at a peak rate of 48 m a-1 from the mid-2000s to 2018, more than doubling the average rate of retreat (22 m a-1) for the preceding 50-year period. From ~1950 to 2018, the total area of land-based glaciers decreased by 228 km2, with 36% of the glacier loss occurring after the mid-2000s. Simple upscaling of area and volume changes to unmeasured glaciers across the entire PWS resulted in an estimated aggregate glacier mass loss of 379 Gt, equivalent to a 1.047 mm rise in sea level from the 1950s to 2018. Tidewater glaciers respond asynchronously with differing periods of peak area and length loss and lower average rate of retreat compared to land-based glaciers. Glacier retreat correlates with increased summer and winter temperatures and decreased winter precipitation. I manually digitize outlines from historical maps, topographic maps, and Landsat images for glaciers 10 km2 or larger. Each study glacier is identified by a project identification number; Global Land Ice Measurements (GLIMS) and Randolph Glacier Inventory (RGI) identification numbers; and glacier name, if available. I manually digitize and adjust glacier boundaries based on the interpretation of 1950/57 topographic maps and Landsat images acquired in 1973/75, 1986, 1994, 2004/06, and 2018. Glacier length changes are measured from the intersection of the centerline with each glacier terminus. I repeat measurements for 1950/57 topographic maps and the Landsat images acquired in 1973/75, 1986, 1994, 2004/06, and 2018, resulting in a glacier length change chronology for each glacier. Glacier outlines are available from the GLIMS database (www.glims.org). See disclaimer in the "Data" section.