ABoVE: Soil Temperature Profiles at USArray Seismic Stations, Alaska, 2016-2018

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.

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.

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.

Project: Arctic-Boreal Vulnerability Experiment (ABoVE)

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.

Acknowledgements: 

This work was funded by NASA ABoVE, grant NNX16AH96G.

Spatial Coverage: Alaska

ABoVE Reference Locations:

Domain: Core ABoVE

State/Territory: Alaska

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
Alaska	-165.35	-150.68	71.00	61.93

 

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.

Column Name	Units/Format	Description
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.
tsoil_x	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.

Column Name	Units/Format	Description
FID		Sort order ID for each site.
Shape	Point, line, or polygon	Shapefile feature type. “Point” in all instances.
StName		Site name.
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.

 

Companion Files

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.

Column Name	Units/Format	Description
site_name		Name of site.
site_code		Site ID.
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.

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.

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.

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.