Thaw depth measurements from the Circumpolar Active Layer Monitoring (CALM) project for site 'Marshall' (U45), Alaska Interior, United States (Alaska) from 2009-2013

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 .

环极地活动层监测计划（Circumpolar Active Layer Monitoring, CALM）的核心目标，是在多年代际的时间尺度上，观测活动层与近地表多年冻土对气候变化的响应。该计划的观测网络始建于20世纪90年代，在南北半球的200余个站点开展观测，以监测活动层与近地表多年冻土随气候波动及变化产生的长期响应。目前，CALM已有来自15个国家的参与方。
多数站点以1公顷至1平方千米的网格为观测尺度，测量活动层厚度并同步观测土壤温度。CALM网络的绝大多数站点位于北极与亚北极低地；其南半球分支（CALM-South）已完成筹备，当前涵盖南极及南美洲的相关站点。
本项目的科学意义与深远影响基于如下假说：活动层厚度的大范围系统性变化，可能对温室气体通量、寒区人类基础设施以及地表过程产生深远影响。因此，在年代际周期内持续推进观测与分析工作，以评估变化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试验（International Tundra Experiment），自1998年起便获得美国国家科学基金会（National Science Foundation, NSF）的持续独立资助。当前，CALM由NSF资助项目1304555（极地项目计划）提供支持。
本数据集与元数据记录，是应项目协调方的要求，通过对原始项目页面https://www2.gwu.edu/~calm/data/north.htm 进行网络爬取自动生成的。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。