ABSTRACT

Snowmelt controls important physical and ecological processes and is widely expected to occur earlier under most climate change scenarios. The western United States (US) is dependent on seasonal snowpack for water resources and recreation, and this diverse landscape is likely to experience continued changes to snowmelt timing that will differ across the domain. In this study, we use NASA’s cloud gap-filled snow-cover maps (MOD10A1F and MYD10A1F) to detect trends in snowmelt timing for hydrologic years 2001–2018. We find that 7.04% of the snow zone (i.e., areas with 10+ years of snow throughout the study period) of the western US is experiencing statistically significant (α = 0.05) trends of earlier snowmelt, while 2.62% of the snow zone is experiencing significant trends of later snowmelt. Analyses at the ecoregion level reveal regional trends, with many southwestern ecoregions experiencing large areas of dramatically earlier snowmelt (e.g., 19.84% of the Mojave Basin and Range). Interestingly, the North Cascades and the Northern Rockies ecoregions have substantial areas of later snowmelt (5.45% and 4.99%, respectively). Our work builds upon previous estimates of snowmelt timing to identify an overall trend of earlier snowmelt while highlighting the high spatial variability in snowmelt trends throughout the western US.

摘要

融雪控制着重要的物理和生态过程，在大多数气候变化情况下，人们普遍预期融雪会更早发生。美国西部（US）依赖季节性积雪来获取水资源和娱乐，而这种多样的景观很可能会经历融雪时间的持续变化，这将在整个地区有所不同。在这项研究中，我们使用NASA的云隙填充的积雪地图（MOD10A1F和MYD10A1F）来检测2001-2018年水文融雪时间的趋势。我们发现美国西部7.04％的降雪区（即整个研究期间有10年以上积雪的地区）正经历着较早融雪的统计学显着（α= 0.05）趋势，而2.62％的降雪区是经历了后来融雪的重大趋势。在生态区域一级的分析揭示了区域趋势，许多西南部生态区的融雪时间大大提前（例如，莫哈韦盆地和山脉的19.84％）。有趣的是，北喀斯喀特和北洛矶山脉生态区有大量后期融雪区（分别为5.45％和4.99％）。我们的工作建立在先前对融雪时间的估计基础上，以确定早期融雪的总体趋势，同时强调了整个美国西部融雪趋势的高度空间变异性。