Accelerated retreat of coastal glaciers in the Western Prince William Sound, Alaska

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 multitemporal 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, geographic information systems (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 fifty-year period. From ~1950 to 2018, the total area of land-based glaciers decreased by 228 km², with 36 percent 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.