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

Documentation Revision Date: 2019-05-08

Dataset Version: 1

Summary

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.

Figure 1. Map showing USArray measurement sites. Sites are labeled with site ID and maximum measurement depth and color-coded by mean annual ground temperature (MAGT in degrees C) of the deepest sensor measurements. Data are omitted for sites disrupted by bears. Data from USArray_Data2018.shp.

Citation

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

  1. Dataset Overview
  2. Data Characteristics
  3. Application and Derivation
  4. Quality Assessment
  5. Data Acquisition, Materials, and Methods
  6. Data Access
  7. References

Dataset Overview

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.

ProjectArctic-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.

Data Characteristics

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.

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.

Quality Assessment

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.

Data Access

These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

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

Contact for Data Center Access Information:

References

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.