Streamflow seasonality in a snow-dwindling world

• 成果类型: Article
• 署名作者: Han, Juntai; Liu, Ziwei; Woods, Ross; Mcvicar, Tim R.; Yang, Dawen; Wang, Taihua; Hou, Ying; Guo, Yuhan; Li, Changming; Yang, Yuting
• 署名单位: Tsinghua University; University of Bristol; Commonwealth Scientific & Industrial Research Organisation (CSIRO); CSIRO Environment
• 刊物名称: Nature
• ISSN/ISSBN: 0028-5585
• DOI: 10.1038/s41586-024-07299-y
• 发表日期: 2024-05-30
• 关键词: climate-change; sierra-nevada; runoff; variability; precipitation; TRENDS; california; impacts; temperature; rainfall

摘要

Climate warming induces shifts from snow to rain in cold regions1, altering snowpack dynamics with consequent impacts on streamflow that raise challenges to many aspects of ecosystem services2-4. A straightforward conceptual model states that as the fraction of precipitation falling as snow (snowfall fraction) declines, less solid water is stored over the winter and both snowmelt and streamflow shift earlier in season. Yet the responses of streamflow patterns to shifts in snowfall fraction remain uncertain5-9. Here we show that as snowfall fraction declines, the timing of the centre of streamflow mass may be advanced or delayed. Our results, based on analysis of 1950-2020 streamflow measurements across 3,049 snow-affected catchments over the Northern Hemisphere, show that mean snowfall fraction modulates the seasonal response to reductions in snowfall fraction. Specifically, temporal changes in streamflow timing with declining snowfall fraction reveal a gradient from earlier streamflow in snow-rich catchments to delayed streamflow in less snowy catchments. Furthermore, interannual variability of streamflow timing and seasonal variation increase as snowfall fraction decreases across both space and time. Our findings revise the 'less snow equals earlier streamflow' heuristic and instead point towards a complex evolution of seasonal streamflow regimes in a snow-dwindling world. Analysis of streamflow measurements from 1950 to 2020 across 3,049 snow-affected catchments over the Northern Hemisphere shows that seasonal streamflow occurs earlier in snow-heavy catchments but later in less snowy regions.