Dataset: 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 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.

通过对历史地图与陆地卫星（Landsat）影像的分析可知，威廉王子湾（Prince William Sound, PWS）西部的沿岸冰川自小冰期（Little Ice Age）结束以来便持续退缩，且在2000年代中期后退缩速率显著加快。本研究结合历史野外观测数据、地形图与Landsat影像，构建了包含43条冰川的多时相编目数据集。冰川面积与长度的测量值源自数字化轮廓，而冰川中心线则通过基于地理信息系统（Geographic Information System, GIS）的半自动算法提取得到。2000年代中期至2018年期间，陆上冰川的退缩峰值速率达48米/年，较此前50年的平均退缩速率（22米/年）提升了一倍以上。1950年至2018年期间，研究区内陆上冰川的总面积减少了228平方千米，其中36%的冰川消融发生在2000年代中期之后。将研究区内未测量冰川的面积与体积变化进行简单尺度外推后，估算得到整个威廉王子湾的冰川总质量损失达379吉吨（Gt），相当于1950年至2018年间海平面上升1.047毫米。潮汐冰川的响应过程具有异步性，其面积与长度退缩峰值出现的时段各不相同，且平均退缩速率低于陆上冰川。冰川退缩与夏季、冬季气温升高以及冬季降水减少存在显著相关性。本研究对面积≥10平方千米的冰川，从历史地图、地形图及Landsat影像中手动数字化其轮廓。每条研究冰川均通过项目编号、全球陆地冰测量（Global Land Ice Measurements, GLIMS）编号、兰道夫冰川编目（Randolph Glacier Inventory, RGI）编号以及冰川名称（如可获取）进行标识。本研究基于1950/57年地形图以及1973/75年、1986年、1994年、2004/06年与2018年获取的Landsat影像解译结果，手动数字化并调整冰川边界。冰川长度变化量通过中心线与各冰川末端的交点进行测算。针对1950/57年地形图以及1973/75年、1986年、1994年、2004/06年与2018年的Landsat影像，本研究重复开展测量工作，最终得到每条冰川的长度变化年表。冰川轮廓数据可从全球陆地冰测量数据库（GLIMS, www.glims.org）获取。详见"Data"板块中的免责声明。