Thaw depth measurements from the Circumpolar Active Layer Monitoring (CALM) project for site 'Hess Creek' (U49), Alaska Interior, United States (Alaska) from 2009-2016

The primary goal of the Circumpolar Active Layer Monitoring (CALM) program is to observe the response of the active layer and near-surface permafrost to climate change over long (multi-decadal) time scales. The CALM observational network, established in the 1990s, observes the long-term response of the active layer and near-surface permafrost to changes and variations in climate at more than 200 sites in both hemispheres. CALM currently has participants from 15 countries. Majority of sites measure active-layer thickness on grids ranging from 1 hecatre to 1 square kilometer, and observe soil temperatures. Most sites in the CALM network are located in Arctic and Subarctic lowlands. Southern Hemisphere component (CALM-South) is being organized and currently includes sites in Antarctic and South America. The broader impacts of this project are derived from the hypothesis that 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 processes. It is therefore critical that observational and analytical procedures continue over decadal periods to assess trends and detect cumulative, long-term changes. The CALM program began in 1991. It was initially affiliated with the International Tundra Experiment and has been supported independently and continuously since 1998 through grants from the United States National Science Foundation (NSF). CALM is funded by the NSF Award 1304555 (Polar Programs). This dataset and metadata record was automatically generated from a web crawl of the original project page https://www2.gwu.edu/~calm/data/north.htm at the request of project coordinators. More information about this site and others in the project can be found at https://www2.gwu.edu/~calm/data/north.htm and also http://gtnpdatabase.org/activelayers .环北极活动层监测（Circumpolar Active Layer Monitoring, CALM）计划的核心目标，是在多年代际的长期时间尺度上，观测活动层（active layer）与近地表多年冻土（near-surface permafrost）对气候变化的响应。该项目的观测网络始建于20世纪90年代，在南北两个半球的200余个站点，长期监测活动层与近地表多年冻土对气候变迁与波动的响应。目前CALM已有15个国家的参与方。绝大多数站点在1公顷至1平方公里的网格范围内开展活动层厚度测量，并同步监测土壤温度。CALM观测网络的多数站点坐落于北极与亚北极低地。南半球分支（CALM-South）目前处于筹建阶段，现已纳入南极与南美洲的相关站点。 本项目的深远影响基于如下科学假说：活动层厚度的大范围系统性变化，可能对温室气体通量、寒冷地区人类基础设施以及地表过程产生显著影响。因此，在数十年尺度上持续推进观测与分析工作，以评估趋势并检测累积性长期变化，具有至关重要的意义。 CALM计划始于1991年，最初隶属于国际苔原实验（International Tundra Experiment），自1998年起由美国国家科学基金会（United States National Science Foundation, NSF）独立持续资助，当前资助项目编号为NSF Award 1304555（极地项目）。 本数据集与元数据记录是应项目协调员的要求，通过对原始项目页面https://www2.gwu.edu/~calm/data/north.htm 进行网络爬取而自动生成。如需了解该站点及项目内其他站点的更多信息，可访问https://www2.gwu.edu/~calm/data/north.htm 与http://gtnpdatabase.org/activelayers。