2023-07-06 ロスアラモス国立研究所(LANL)
◆ロスアラモス国立研究所のベネット氏らの研究チームは、永久凍土地域の水文学に関するデータを分析し、長期的な傾向として永久凍土の融解からの流量増加が確認されたことを報告しました。
◆特に、永久凍土の範囲が重要な要素となっており、降水量の増加と温暖化により、流量全体や最小流量が増加していることが示されました。また、永久凍土が支配的な地域では、最大流量とそのタイミングも変動しており、秋と冬に顕著な増加が見られます。これらの結果は、永久凍土が季節ごとの流量の変化においてますます重要な役割を果たしていることを示しています。
＜関連情報＞
- https://discover.lanl.gov/news/0706-climate-change/
- https://www.frontiersin.org/journals/water/articles/10.3389/frwa.2023.1099660/full
北米の永久凍土流域における最近の流出傾向
Recent streamflow trends across permafrost basins of North America
Katrina E. Bennett, Jon Schwenk, Claire Bachand, Eve Gasarch, Jemma Stachelek, William R. Bolton and Joel C. Rowland
Frontiers Published:29 June 2023
DOI:https://doi.org/10.3389/frwa.2023.1099660
Introduction: Climate change impacts, including changing temperatures, precipitation, and vegetation, are widely anticipated to cause major shifts to the permafrost with resulting impacts to hydro-ecosystems across the high latitudes of the globe. However, it is challenging to examine streamflow shifts in these regions owing to a paucity of data, discontinuity of records, and other issues related to data consistency and accuracy.
Methods: Recent trends for long-term periods (1990–2021, 1976–2021) in observed minimum, mean, and maximum seasonal and annual streamflow were analyzed for a range of watersheds across North America affected by varying degrees of permafrost coverage.
Results: Streamflow trend analysis revealed that areas affected by permafrost are changing variably over the periods in terms of maximum, mean, and minimum seasonal and annual streamflow. These changes indicate a significant shift occurring in the most recent 46 years towards increasing mean streamflow for the dominant (> 50%) permafrost systems. Meanwhile, minimum streamflow increases for all permafrost-dominant systems and many of the other permafrost-affected systems across the seasons and annual periods considered, with the greatest number of significant changes in streamflow over other metrics. Maximum streamflow is shifting variably with significant increases in the permafrost-dominant systems in winter and fall over longer time periods of analysis. Our analysis suggests that streamflow trends are driven by climate (precipitation, followed by temperature), while variables such as permafrost coverage only appear important in the most recent 32-year period.
Discussion: The increases in streamflow trends observed in this study are reflective of deepening active layers and thawing permafrost, indicating that the entire hydrograph is undergoing change within permafrost-dominant streamflow systems as the Arctic moves towards a warmer future under climate change. Despite the many challenges to understanding changing streamflow in cold regions, there are new products and datasets in development that are increasingly allowing researchers to better understand the patterns of change in Arctic and subarctic systems affected by permafrost, offering a range of new tools, which, along with continued observational records, may help in improved understanding of changing Arctic streamflow patterns.
