Seasonal soil active layer measurements from a Circumpolar Active Layer monitoring (CALM) grid, (R16) Segodnya Pingo, Kolyma, Russia. 1996-2020.

The Circumpolar Active Layer Monitoring (CALM) program represents the only coordinated program providing collection, standardization, open access, and dissemination of active-layer data world-wide. Widespread, systematic changes in the thickness of the active layer could have profound effects on the flux of greenhouse gases, on the human infrastructure in cold regions, and on landscape and hydrologic processes. It is therefore critical that observational and analytical procedures continue over decadal periods to assess trends and detect cumulative, long-term changes. This dataset contains active-layer observations conducted by the CALM program since the 1990s, supported by a series of National Science Foundation (NSF) awards. CALM program is an integral part of the Global Terrestrial Network for Permafrost. CALM 2020 data are significantly reduced due to pandemic-related travel restrictions. Available 2020 data are limited in terms of extent, and observations were not as controlled as previous years in terms of measurement timing or method, and therefore should be treated with caution.

环极活动层监测（Circumpolar Active Layer Monitoring, CALM）计划是全球范围内唯一协调开展活动层（active layer）数据收集、标准化、开放获取与传播的项目。活动层厚度的广泛、系统性变化可能对温室气体通量、寒冷地区的人类基础设施以及景观和水文过程产生深远影响。因此，至关重要的是，观测与分析程序需持续数十年，以评估趋势并检测累积性的长期变化。本数据集包含CALM计划自20世纪90年代以来开展的活动层观测数据，这些观测得到美国国家科学基金会（National Science Foundation, NSF）一系列资助的支持。CALM计划是多年冻土全球陆地网络（Global Terrestrial Network for Permafrost）的重要组成部分。受疫情相关旅行限制影响，CALM 2020年的数据量显著减少。现有2020年数据的覆盖范围有限，且观测在测量时间或方法上的控制程度不及往年，因此使用时需谨慎。