P2C2: Spatiotemporal Variability in Western United States Snowpack During the Common Era

自1950年以来，美国西部每年的积雪和融雪供应都在恶化。虽然气候预估表明这些趋势将在整个21世纪持续下去，但短期的仪器积雪记录阻止了对这些近期下降是否超出长期积雪变率的自然范围的评估，或者它们是否相对于前几个世纪是异常的。长期降雪观测的缺乏也使得难以确定和描述年积雪积累的年代际尺度和较长期气候驱动因素、这些驱动因素随时间和空间的变化以及雪系统内部变率的大小。然而，这些时间尺度上的信息对于有效地适应气候变化最为重要。为了解决这些关键的知识空白，该项目将开发跨越美国西部的雪水当量网格空间场重建，在使用树木年轮的模式校准中明确捕获负雪趋势时期。研究人员的目标是测试气候模型在过去一千年里模拟美国西部强迫和内部雪水气候变化范围的能力。潜在的更广泛的影响包括产生长雪水当量（SWE）树木年轮年表，以检验工业化前时间尺度上环境强迫的不同假设，并将其与上一千年气候模式输出进行比较；测试过去30年相对于工业化前强迫的SWE变化的可能的人为指纹，以及对未来水资源管理的可能影响；以及一位早期职业科学家的支持，这位科学家帮助开创了树轮SWE学科。该项目还支持一名本科生、一名博士后研究科学家，并向北美西部的水资源管理人员提供服务。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Annual snowpack and snow meltwater supplies have deteriorated across the western United States since 1950. While climate projections indicate these trends will continue throughout the 21st century, short instrumental snow records prevent an assessment of whether these recent declines fall outside the natural range of long-term snowpack variability or if they are exceptional relative to prior centuries. A lack of long snow observations also makes it difficult to identify and characterize decadal-scale and longer-term climatic drivers of annual snow accumulation, changes in those drivers over time and space, and the magnitude of internal variability in the snow system. Yet information at these timescales are most important for effective climate change adaptation. To address these critical knowledge gaps, this project will develop gridded spatial field reconstructions of snow water equivalent spanning the western United States that explicitly capture the period of negative snow trend within model calibrations using tree rings. The researchers aim to test the ability of climate models to simulate the range of forced and internal snow hydroclimate variability in western United States over the last millennium.The potential Broader Impacts include the generation of long Snow Water Equivalent (SWE) tree ring chronologies to test different hypotheses of environmental forcing on the pre-industrial timescales and their comparison with last millennium climate model output; the testing of a possible anthropogenic fingerprint on changes in SWE over the last thirty years relative to pre-Industrial forcing and the possible implications for water resource management in the future; and support of an early-career scientist who has helped pioneer the tree-ring SWE discipline. The project also supports an undergraduate student, a post-doctoral research scientist, and outreach to water resource managers in Western North America.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.