NOAA/WDS Paleoclimatology - Meko - Harmon Canyon - PSME - UT530, PAGES North America 2K Version

In western North America, snowpack has declined in recent decades, and further losses are projected through the 21st century. Here, we evaluate the uniqueness of recent declines using snowpack reconstructions from 66 tree-ring chronologies in key runoff-generating areas of the Colorado, Columbia, and Missouri River drainages. Over the past millennium, late 20th century snowpack reductions are almost unprecedented in magnitude across the northern Rocky Mountains and in their north-south synchrony across the cordillera. Both the snowpack declines and their synchrony result from unparalleled springtime warming that is due to positive reinforcement of the anthropogenic warming by decadal variability. The increasing role of warming on large-scale snowpack variability and trends foreshadows fundamental impacts on streamflow and water supplies across the western United States.

北美西部的积雪覆盖（snowpack）在近数十年间已出现衰减，且预计在整个21世纪都将持续发生进一步的积雪损失。本研究借助科罗拉多河、哥伦比亚河与密苏里河流域关键产流区内66个树轮年表（tree-ring chronologies）重建的积雪覆盖数据，评估了近期积雪衰减的独特性。在过去千年的时间尺度上，20世纪后期的积雪衰减在北落基山脉的强度几乎达到前所未有的水平，且在整个北美科迪勒拉山系呈现出显著的南北同步分布特征。积雪衰减及其空间同步性，均由前所未有的春季升温所驱动——该升温源于年代际变率（decadal variability）对人为变暖（anthropogenic warming）的正增强效应。升温对大尺度积雪覆盖变化与趋势的影响日益凸显，这预示着美国西部全域的河川径流与供水系统将受到根本性影响。