Thaw depth measurements from the Circumpolar Active Layer Monitoring (CALM) project for site 'Eagle' (U51), 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，观测活动层与近地表多年冻土对气候变化的响应。该计划于1990年代建立的观测网络，在全球两个半球的200余个站点，长期监测活动层与近地表多年冻土对气候变化及其波动的响应。目前，CALM共有来自15个国家的参与方。绝大多数站点以1公顷至1平方千米的网格为基准，测量活动层厚度并观测土壤温度。CALM观测网络的多数站点分布在北极与亚北极低地地区。南半球分支（CALM-South）目前仍在筹建中，当前已纳入南极与南美洲的部分站点。本项目的深远意义源于一项核心假说：活动层厚度的大范围系统性变化，可能会对温室气体通量、寒区人类基础设施以及地表过程产生深远影响。因此，在数十年的时间尺度上持续开展观测与分析工作，对于评估变化趋势、捕捉累积性长期变化至关重要。CALM计划始于1991年，最初隶属于国际冻原实验（International Tundra Experiment），并自1998年起获得美国国家科学基金会（United States National Science Foundation, NSF）的资助，实现了独立且持续的运营。本次项目由美国国家科学基金会极地项目（Polar Programs）下的编号为1304555的资助项目支持。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的。如需了解本项目站点及其他相关信息，可访问https://www2.gwu.edu/~calm/data/north.htm 与http://gtnpdatabase.org/activelayers 。