Documentation Revision Date: 2019-05-08
Dataset Version: 1
Data include 20 data files, one per site, in comma-separated (.csv) format and one compressed shapefile (.zip) with site locations. The data in the shapefile are also provided as a companion file in .kmz format for viewing in Google Earth.
Nicolsky, D.J., V.E. Romanovsky, A.L. Kholodov, K. Dolgikh, and N. Hasson. 2019. ABoVE: Soil Temperature Profiles at USArray Seismic Stations, Alaska, 2016-2018. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1680
Table of Contents
- Dataset Overview
- Data Characteristics
- Application and Derivation
- Quality Assessment
- Data Acquisition, Materials, and Methods
- Data Access
This dataset includes soil temperature profile measurements taken three times per day at 20 seismic monitoring sites associated with the USArray program, located across the NASA ABoVE domain in interior Alaska. Data were collected primarily from the summer of 2017 through the summer of 2018. At one station, measurements start in 2016. These measurements were taken using temperature probes installed at four depths from the surface to a target maximum depth of 1.5 meters and recorded with HOBO data loggers.
The Arctic-Boreal Vulnerability Experiment (ABoVE) is a NASA Terrestrial Ecology Program field campaign in Alaska and western Canada from 2016 to 2021. Research for ABoVE will link field-based, process-level studies with geospatial data products derived from airborne and satellite sensors, providing a foundation for improving the analysis, and modeling capabilities needed to understand and predict ecosystem responses and societal implications.
This work was funded by NASA ABoVE, grant NNX16AH96G.
Spatial Coverage: Alaska
ABoVE Reference Locations:
Domain: Core ABoVE
Grid cell(s): Ch038v008, Ch041v015, Ch046v017, Ch036v006, Ch036v017, Ch034v004, Ch043v005, Ch040v006, Ch041v009, Ch050v009, Ch045v010, Ch035v012, Ch040v012, Ch049v012, Ch042v013, Ch046v013, Ch045v014, Ch014v018, Ch048v018, Ch021v026
Spatial Resolution: Point locations
Temporal Coverage: Three measurements per day
Study Area (all latitude and longitude given in decimal degrees)
|Site||Westernmost Longitude||Easternmost Longitude||Northernmost Latitude||Southernmost Latitude|
Data File Information
This dataset includes 21 data files; 20 files in comma-separated (.csv) format with soil temperature data and one compressed shapefile (.zip) showing site locations. In addition, three companion files are provided; (1) a comma-separated (.csv) file containing information about each collection site, (2) a .kmz file for quick visualization of the site locations in Google Earth, and (3) a pdf copy of this User Guide.
Soil Temperature CSV Files:
All site-specific data filenames consist of the sitename followed by the first and last day of data contained within the file, in the format sitename_YYYY-MM-DD_YYYY-MM-DD.csv
Example filenames: A19K-1_2017-09-28_2018-08-17.csv or C18K-1_2017-08-29_2017-09-21.csv
Missing data in the .csv files are represented as -9999.
Table 2. Variables in the .csv data files.
|date_time||YYYY-MM-DD HH:MM||Date and time that a measurement was taken, in Alaskan standard time.|
|timezone||Time zone for date_time column; “AKST” in all instances.|
|degrees Celsius||Soil temperature measured at a depth of x meters. Typically there are four columns of temperature data representing measurements at four different depths.|
Spatial Data Information: The shapefile USArray_Data2018.shp is provided in the spatial reference system EPSG: 4326. This file provides site locations and terrain observations. Each site is stored as a point.
Table 3. Variables in the file USArray_Data2018.shp.
|FID||Sort order ID for each site.|
|Shape||Point, line, or polygon||Shapefile feature type. “Point” in all instances.|
|Lat||Decimal degrees||Site latitude in decimal degrees.|
|Lon||Decimal degrees||Site longitude in decimal degrees.|
|Max_depth||m||Maximum depth at which soil temperature was collected.|
|MAGT||Degrees Celsius||Mean annual ground temperature. MAGT is the annual average of the deepest sensor measurements.|
|days||days||Number of days of data collection|
|bears_fail||“x” means that the sensors at the site were destroyed by bears.|
|date_remov||YYYY-MM-DD||Date (AKST) that sensors were removed if applicable.|
|spec_note||Note detailing the removal of sensors.|
Three companion files are provided; (1) sites_metadata.csv : a comma-separated (.csv) file containing information about each collection site, (2) USArray_Data2018.kmz: a .kmz file for quick visualization of the site locations in Google Earth, and (3) a pdf copy of this User Guide.
Table 4. Variables in companion file, sites_metadata.csv.
|site_name||Name of site.|
|latitude||decimal degrees||Latitude of site.|
|longitude||decimal degrees||Longitude of site.|
|land_owner_manager||Land owner or manager of collection site.|
|nearest_hubs||Research hub or hubs closest to the collection site, and their distance in NM.|
|nearby_landmark||A landmark close to the site.|
|elevation||m||Altitude of site in meters.|
|slope||Degrees||Slope of site in degrees.|
|veg_type||Type of biome.|
|vegetation||Written description of the plants at the site.|
|terrain||Written physical description of the terrain.|
|slope/aspect_description||Description of the slope or aspect of the site.|
|soil/bedrock||Notes related to the soil or bedrock of the site.|
|field_notes||Miscellaneous notes regarding the site.|
|access||Means of accessing the site.|
|max_depth||m||Maximum measurement depth.|
|installation_date||YYYY-MM-DD||Date when sensors were installed. Time zone is AKST.|
|further_notes||Miscellaneous notes related to sensor failure or methodology.|
Application and Derivation
The ground temperature variability across the Arctic landscape depends on air temperature, snow cover, moisture content, vegetation, terrain, soil properties, and related environmental variables. A juxtaposition of all these factors results in a highly heterogeneous distribution of ground temperature, active layer thickness and permafrost conditions. As a result, prediction of subsurface temperature dynamics remains challenging, and mean temperatures for a study region may not account for "hot spots" of change, which alone could significantly contribute to thaw and associated carbon emissions. A solution is to sample (record) temperature regimes within different ecotypes and environmental conditions, and build a portfolio of subsurface thermal regimes across various ground conditions. The ground temperature profilers demonstrated here will supplement the existing data loggers and provide means to sample the ground temperature regime in currently underrepresented ecotypes to increase our knowledge of permafrost variability across Alaska and Northern Canada.
All specs on HOBO data logger and cable accuracy, resolution, range, can be found at the manufacturer's webpage (Onset Computer Corporation) listed in the "references" section. Sensors were calibrated in an ice bath at Permafrost Lab to determine certainty of temperature. Temperature attained during the calibration is subtracted from the regular measurement result. Installation depth uncertainty is +/- 0.025m.
All data were analyzed for anomalies, identified and documented (sensors failed or pulled out by bears). Details for these anomalies, or "bear fails", are in the companion file, sites_metadata.csv.
Data Acquisition, Materials, and Methods
All sites are at seismic stations associated with the USArray program, detailed on the Earthscope website at http://www.usarray.org/ . Twenty (20) stations were initially established, but sensors at 6 of the stations were destroyed by bears; data files for these sites include data collected until the time of destruction.
A slide hammer, attached to a 1.5 m steel rod, was used to make a hole in the ground, 1.6 cm in diameter. Penetration varied with substrate composition, and several attempts were made to reach the target depth of 1.5 m.
Temperature sensors were inserted into the hole, always including one at the bottom and one at a depth between 0.01 m and 0.02 m to represent the ground surface temperature. A typical profile included sensors at 0.01, 0.2, 1.0 and 1.5 m depths. The hole was filled, and the cables leading to the data logger were buried.
Data were collected using Onset HOBO 4 channel UX120-00614 data loggers with 2.5-STEREO cables.
These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).
Contact for Data Center Access Information:
- E-mail: firstname.lastname@example.org
- Telephone: +1 (865) 241-3952
Earthscope, 2019. USArray: A Continental-scale Seismic Observatory. http://www.usarray.org/. Accessed 8 April 2019.
Onset Computer Corporation, 1995-2019. HOBO UX120 4-channel data logger - UX120 - 006M. https://www.onsetcomp.com/products/data-loggers/ux120-006m. Accessed 2 April 2019.