EnviroAtlas - Probabilistic Estimates of the Distribution of Near-surface (within 1m) Permafrost in Alaska

This dataset was created by USGS and is being hosted by US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets). 

The original raster dataset has additional categories to differentiate between permafrost probability areas and other land cover categories. In the USGS raster, values range from 0 to 105, with values above 100 representing the following: 101 = open water; 102 = perennial ice/snow; 103 = developed; 104 = barren, and; 105 = cultivated areas. These values has been modified by the EnviroAtlas team to change values above 100 to "-1" to produce a dataset with modeled likelihood values ranging from 0 to 100 only. 

Abstract: Pastick et al., 2015 : "This medium resolution (i.e. 30-m pixels) spatial dataset provides an estimate of the occurrence of near-surface (within 1 m of the ground surface) permafrost in Alaska.  The dataset was developed using a decision-tree model that statistically and spatially extended late-season field observations (n ~ 17,000) using remotely sensed imagery, climatic data, and thematic maps of a wide range of surface and subsurface biophysical characteristics.  To circumvent the use of seasonal frost observations, only thaw-depth measurements taken during late-season months (late July to mid-September) or measurements designated to have no near-surface (within 1m) permafrost were used for model calibration and validation. Individual pixel values represent the probability of encountering near-surface permafrost (i.e. 0 to 100 %), as derived from a tree ensemble model, and pixel values greater than 100 correspond to masked land cover types (i.e. 101 = open water; 102 = perennial ice/snow; 103 = developed; 104 = barren, and; 105 = cultivated areas) as defined by the 2001 National Land Cover Database.  Decision tree models and resultant maps were tested using independent field observations and f-fold cross validations, which indicated that the map product has an overall accuracy of approximately 85 % when using a probability threshold of 50 % (i.e. less than 50 % = near-surface permafrost absent; greater than or equal to 50 % = near-surface permafrost present)" 

Pastick, N. J., Jorgenson, M. T., Wylie, B. K., Nield, S. J., Johnson, K. D., & Finley, A. O. (2015). Distribution of near-surface permafrost in Alaska: Estimates of present and future conditions. Remote Sensing of Environment, 168, 301-315. https://doi.org/10.1016/j.rse.2015.07.019  

Tags: 020:072, alaska, biology, cleanup, climate, conservation, contaminant, drinking water, ecosystem, ecosystem services, emergency, energy, enviroatlas, environment, environmental atlas, exposure, facilities, ground water, habitat, hazards, impact, imperiled, indicator, land, land cover, management, modeling, natural resources, permits, protected lands, remediation, response, risk, sites, society, soils, spills, surface water, threatened, toxics, transportation, united states, utilities, waste, water
Organization: U.S. Environmental Protection Agency