In many mountainous regions, winter precipitation accumulates as snow that melts in the spring and summer, which provides water to one billion people globally. Climate warming and earlier snowmelt compromise this natural water storage. Although snowpack trend analyses commonly focus on the snow water equivalent (SWE), we propose that trends in the accumulation season snowmelt serve as a critical indicator of hydrological change. Here we compare long-term changes in the snowmelt and SWE from snow monitoring stations in western North America and find 34% of stations exhibit increasing winter snowmelt trends (P < 0.05), a factor of three larger than the 11% showing SWE declines (P < 0.05). Snowmelt trends are highly sensitive to temperature and an underlying warming signal, whereas SWE trends are more sensitive to precipitation variability. Thus, continental-scale snow water resources are in steeper decline than inferred from SWE trends alone. More winter snowmelt will complicate future water resource planning and management.

在许多山区，冬季降水以积雪的形式在春季和夏季融化，为全球 10 亿人提供水源。气候变暖和早期融雪破坏了这种天然的储水能力。尽管积雪趋势分析通常集中在雪水当量（SWE）上，但我们认为积累季节融雪的趋势是水文变化的关键指标。在这里，我们比较了北美西部积雪监测站的融雪和 SWE 的长期变化，发现 34% 的站点表现出冬季融雪趋势增加（P  < 0.05），比显示 SWE 下降的 11% 大三倍（磷 < 0.05)。融雪趋势对温度和潜在的变暖信号高度敏感，而 SWE 趋势对降水变化更敏感。因此，大陆尺度的雪水资源比仅从 SWE 趋势推断的下降幅度更大。更多的冬季融雪将使未来的水资源规划和管理复杂化。