Thaw depth measurements from the Circumpolar Active Layer Monitoring (CALM) project for site 'Toolik 1 km grid' (U12 A), Alaska North Slope, United States (Alaska) from 1995-2018

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）项目的核心目标，是在多年代际的长期时间尺度下，观测活动层与近地表多年冻土对气候变化的响应。该项目的观测网络始建于20世纪90年代，在南北半球共计200余个站点开展观测工作，以监测活动层与近地表多年冻土对气候波动与变化的长期响应。目前CALM共有来自15个国家的参与方。多数站点以1公顷至1平方公里的网格为基准，开展活动层厚度测量与土壤温度监测。CALM观测网络的绝大多数站点分布于北极与亚北极低地。南半球分支（CALM-South）目前仍在组建中，现已涵盖南极与南美洲的观测站点。本项目的深远意义依托于下述科学假说：活动层厚度的大范围系统性变化，可能对温室气体通量、寒区人类基础设施以及景观过程产生显著影响。因此，持续开展多年代际的观测与分析工作，以评估变化趋势并检测累积性长期变化，至关重要。CALM项目始于1991年，最初隶属于国际苔原试验计划（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）的持续独立资助。当前CALM由NSF资助编号1304555的极地项目计划（Polar Programs）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。更多关于该站点及项目内其他站点的信息，可访问https://www2.gwu.edu/~calm/data/north.htm与http://gtnpdatabase.org/activelayers 获取。