This data product contains field data measurements of air temperatures and thaw depth (active-layer thickness) measured at locations in north-central Alaska, and modelled values of air temperatures and thaw depth extrapolated to an area encompassing the Kuparuk River basin of north-central Alaska. Air temperature and thaw depth were measured in the years 1995, 1996, and 1997; air temperature was measured at 10 core Flux Study plots and additional sites, and thaw depth was measured within each of seven ARCSS 1 km x 1 km grids. The data were collected to provide a basis for extrapolating thawing degree-days and thaw depth to the landscape scale (the Kuparuk River basin).
Modelled air temperatures derived from the 1995 air temperature measurements are represented in 787 x 371 element matrices of thawing degree-day sums at weekly intervals for part of summer 1995. Thaw depth matrices were modelled using the interpolated thawing degree-day data, a vegetation map of the Kuparuk River basin, and a digital elevation model (DEM) of the same area. Modelled thaw depth is represented in 178 x 369 element matrices of active-layer thickness at weekly intervals for part of summer 1995, one time period in 1996, and "end-of-season" (August 6) 1997.
Measurements were taken as part of the Land-Atmosphere-Ice Interactions - Arctic Transitions in the Land-Atmosphere System (LAII-ATLAS) program. The research project was funded by the Arctic System Sciences (ARCSS) Program, grant number OPP-9612647.
Data are available by FTP.
Nelson, F.E. 1996. Air Temperature and Thaw Depth, North Slope, Alaska: Field Measurements (1995-97) and Computed Values. Boulder, CO: National Center for Atmospheric Research
|Data format||Tab-delimited text files|
|Spatial coverage||Data were collected from sites in Alaska, located between 68.382º N and 70.539º N, and between 148.089º W and 151.189º W.|
|Temporal coverage||Data were collected from 1995-07-07 to 1997-08-20|
|File naming convention||See File Naming Convention for details|
|File size||15 KB to 2,311 KB|
|Parameter(s)||Thaw depth (active layer thickness) and air temperature|
Data are available as tab-delimited text files.
The data files are organized in the following directories and subdirectories:
field_meas/ - directory containing subdirectories pertaining to field measurements
field_meas/airtemp - subdirectory containing files of air temperature measurements
field_meas/thawdepth - subdirectory containing subdirectories of thaw depth measurements
field_meas/thawdepth/thaw95 - subdirectory containing files of thaw depth measurements in 1995
field_meas/thawdepth/thaw96 - subdirectory containing files of thaw depth measurements in 1996
field_meas/thawdepth/thaw97 - subdirectory containing files of thaw depth measurements in 1997
modelled/ - directory containing subdirectories pertaining to modelled data
modelled/degreedays - subdirectory containing files of modelled degree-days
modelled/thawdepth - subdirectory containing subdirectories of modelled thaw depth
modelled/thawdepth/thaw95 - subdirectory containing files of modelled thaw depth, 1995
modelled/thawdepth/thaw97 - subdirectory containing files of modelled thaw depth, 1997
Each data file name contains the plot name and number. For example,
Each file has six columns:
All temperatures are expressed in degrees Celsius.
For more detailed information on the individual sites, please refer to the file field_air_temp_site_descriptions.txt.
Each file represents one grid and one probing date. Letters represent location and numbers represent probing date.
The following codes are used for locations.
bet: Betty Pingo
hv: Happy Valley
imn: Imnuviat Creek
to: Toolik Lake
wd: West Dock
Each file contains a square array of 121 numbers. Each of the 121 numbers represents the average of two thaw-depth measurements at a grid stake. The 11 rows and 11 columns in each file represent, respectively, the E-W ows and N-S columns of the Alaskan grids. Adjacent data points have an implicit horizontal spacing of 100 m.
Numbers in the files are arranged as follows:
|NW Corner||11c||NE Corner|
|SW Corner||--||SE Corner|
The following codes are used for missing data:
200: lakes and deep standing water
300: rocks, gravel, roads, etc.
The file gridstat.all contains summary statistics for each of the North Slope grids on all probing dates in 1995, 1996, and 1997. Each record is composed of the following information, in the order shown:
number of observations
These data contain a 787 x 371 matrix of cumulative thawing-degree day sums for six dates in 1995:
ddt710.txt - July 10
ddt717.txt - July 17
ddt724.txt July 24
ddt731.txt - July 31
ddt806.txt - August 06
ddteos.txt - "End Of Season" (August 11), the last date for which simultaneous records are available.
Summations began on June 23, 1995, and extended through August 11, 1995. Temporal coverage begins 1995-07-07.
Each file begins with four header records, which are compatible with the commercial mapping program "SURFER for Windows" (Golden Software, Golden Colorado). The headers are as follows:
DSAA: indicates that file appears as ASCII text
xmin, xmax: minimum and maximum longitude values, expressed as meters in the UTM coordinate system (Zone 6)
ymin, ymax: minimum and maximum latitude values, expressed as meters in the UTM coordinate system (Zone 6), with 7,000,000 meters subtracted from Y-coordinates
zmin, zmax: minimum and maximum thaw depth values, expressed in centimeters
The 787 x 371 matrix of active-layer thickness follows the four headers. The top row is the southernmost part of the matrix; this is the "SURFER for Windows" protocol. If other programs are to be used to map the data, the matrix should be rewritten. The "Mirror Y" function in Surfer for Windows will perform this task.
These data contain a 785 x 369 matrix of active-layer thickness for each of the six dates in 1995, cited above in Modelled Measurements: Degree Days. The files are registered to the Kuparuk DEM, but lack the top and bottom rows and the outermost right and left columns, which were expended in the slope and aspect calculations necessary to compute solar radiation receipts.
Each file begins with four header records, which are compatible with the commercial mapping program "SURFER for Windows" (Golden Software, Golden, Colorado). The headers are as follows:
DSAA: indicates that file appears as ASCII text.
xmin, xmax: minimum and maximum longitude values, expressed as meters in the UTM coordinate system.
ymin, ymax: minimum and maximum latitude values, expressed as meters in the UTM coordinate system.
zmin, zmax: minimum and maximum thaw depth values, expressed in centimeters.
The 785 x 369 matrix of active-layer thickness (expressed in cm) follows the four headers. The top row is the southernmost part of the matrix. This is the "SURFER for Windows" protocol. If other programs are used to map the data, the matrix should be rewritten with north at the top. The "Mirror Y" function in Surfer for Windows will accomplish this task.
All negative numbers refer to codes in Walker's vegetation map for which a thaw depth could not be computed (water, barrens, clouds, ice, etc.). These codes, which are different from those used on the digital version of the original Walker vegetation map, were rewritten to save disk space. The new codes are:
This file (thaw97.txt) includes the 1997 "end-of-season" (August 6) map of active-layer thickness for the Kuparuk River basin in north-central Alaska. The general procedures used to develop the map are described in detail in the publication by Nelson et al. (1997). Major departures from the 1995 and 1996 maps include the following:
As noted above, several new sites were used to compile the 1997 map. Information about each site is given below. The records are in comma-delimited format, with the following column headers:
|site ID||degree-days||elevation (meters)||latitude (degrees)||latitude (UTM northing)||deviation of degree-day sums due to elevation||degree-days of thawing, adjusted to sea level|
Note: Degree days represent degree days (in Celsius) of thawing for the period 1997-06-11 to 1997-08-06.
Sites used to calculate regressions are:
FL-1 moist nonacidic (<200 m of el.)
FL-3 moist nonacidic (>200 m of el.)
FL-4 moist acidic
Wet Betty - wet tundra (<200 m of el.)
FL-6 wet tundra (>200 m of el.)
FL-10 Shrublands (WARNING: for FL10, the regression coefficients developed for 1996 were used. No valid 1997 thaw depth data were available at this location)
File sizes range from 15 KB to 2,311 KB.
Data were collected from within the following geographic coordinates:
Southernmost Latitude: 68.382º N
Northernmost Latitude: 70.539º N
Westernmost Longitude: 151.189º W
Easternmost Longitude: 148.089º W
Data were collected from 1995-07-07 to 1997-08-20.
The parameters measured were thaw depth (active layer thickness) and air temperature.
These files contain processed air temperature data for the flux study plots in north-central Alaska, extending from Prudhoe Bay to Toolik Lake, and for a site adjacent to the airport runway at Deadhorse and one at Mile 56 of the Dalton Highway. Two additional sites (flux sites 13 and 14) were operated during 1996 and 1997. The data set was collected to provide a basis for calculating the depth of thawing associated with particular soil/vegetation associations.
Please refer to the file field_air_temp_site_descriptions.txt for detailed information on soils and vegetation at each plot.
These files contain thaw depths (active-layer thickness) within each of the seven ARCSS 1 km x 1 km grids in northern Alaska for the summers of 1995, 1996, and 1997. The data were collected to obtain extensive information about active layer thickness and its variation (at the landscape scale) at representative geographic locations on the North Slope. Data from these grids have also been used for validating modeling procedures used to estimate active-layer thickness in the Kuparuk River basin, as described by Nelson et al. (1997).
These files contain rectangular, 787 x 371 element matrices of thawing degree-day sums at weekly intervals for part of summer, 1995. The matrices were constructed by spatial interpolation from the flux study plots onto the Kuparuk River basin digital elevation model (DEM). The data set was constructed as a means of extrapolating a limited number of air temperature measurements over the entire Kuparuk River basin. The extrapolated temperature fields were used as part of a procedure for calculating active-layer thickness in the Kuparuk basin. The air temperature field measurement data from the individual flux study plots were used to construct these matrices.
These files contain rectangular, 785 x 369 element matrices of active-layer thickness (thaw depth) at weekly intervals for part of summer, 1995. The matrices were constructed using interpolated thawing degree-day data from the flux study plots, D.A. Walker's vegetation map of the Kuparuk River basin, and a digital elevation model (DEM) of the same area. The data set was constructed as a means of extrapolating a limited number of active-layer measurements to the entire Kuparuk River basin. Please refer to the modelled measurement data for degree days for the interpolated air temperature fields used to compute the thaw-depth matrices.
This file includes the 1997 "end-of-season" (August 6) map of active-layer thickness for the Kuparuk River basin in north-central Alaska. The general procedures used to develop the map are described in detail in Nelson et al. (1997).
Sample air temperatures from field measurements, flux study site 13:
|Date||Tav(C) (mean temp)||Min||Max||Amp||# of meas. a day|
At each plot a "StowAway" miniature data logger, manufactured by Onset Computer Corporation (Pocasset, Massachusetts), was installed. The loggers have a temperature range of -50 to +33 degrees Celsius, and an effective resolution of 0.3 degree Celsius. Each logger/thermistor assembly is given a factory one-point calibration in an ice bath at 0 degrees Celsius. At each field site, the thermistor was placed in a six-plate radiation shield (R.M. Young Co., Traverse City, Michigan) and mounted on a mast at a height of approximately 1.5 meters above the ground surface.
Each logger was configured to measure temperatures at 15-minute intervals during summer (early June to late August) and one-hour intervals in winter (late August to early June). Daily means were calculated as an average of 96 or 24 temperature measurements, respectively.
Each of the ARCSS grids consists of a square 11 x 11 array of steel stakes located at 100 m intervals and surveyed to first-order accuracy. Rows and columns of the grids are oriented E-W and N-S, respectively.
Data were collected on several dates at each of the seven grids. Field procedures involved making two measurements at each of the 121 stakes using a rigid steel rod calibrated in 1 cm increments. Values reported here are the average of these two measurements, and are reported to the nearest cm.
Temperature records were used from datalogger/thermistor assemblies located at the following Flux Study plots: 95-1, 95-2, 95-3, 95-4, 95-6, 95-9, 95-10. Ancillary data from installations at Deadhorse and Happy Valley were also employed. These records were reduced to sea level using the environmental lapse rate of 0.64 degrees Celsius per 100 m elevation. The mean daily temperatures above zero degrees Celsius were then summed to produce cumulative thawing degree days. Polynomial regression was used to develop relations between latitude and degree-day sums for the sea-level data. These relations were interpolated onto the Kuparuk DEM using the lapse rate cited above, providing a degree-day field adjusted for the effects of elevation. The data represent the period June 23 to August 11, inclusive, and are presented at weekly intervals for the period during which thaw-depth observations were made. Note: These Degree-day fields do not represent seasonal totals. They were employed in the original study to develop statistical relationships between partial degree-day sums and active-layer thickness. Analytic procedures are detailed in the manuscript by Nelson et l.(in review) cited below.
Temperature records were used from datalogger/thermistor assemblies located at the following Flux Study plots: 95-1, 95-2, 95-3, 95-4, 95-6, 95-9, 95-10. Ancillary data from installations at Deadhorse and Happy Valley were also employed. These records were reduced to sea level using the environmental lapse rate of 0.64 degrees Celsius per 100 m elevation. The mean daily temperatures above zero degrees Celsius were then summed to produce cumulative thawing degree days. Polynomial regression was used to develop relations between latitude and degree-day sums for the sea-level data. These relations were interpolated onto the Kuparuk DEM using the lapse rate cited above, providing degree-day fields adjusted for the effects of elevation. The data represent the period June 23 to August 11, inclusive. Regression equations relating active-layer thickness to thawing degree-day sums were developed for each of the vegetation/soil associations represented by the Flux Study plots. The categorical values in Walker's vegetation map were then used to compute a thaw depth at each node in the mesh represented by an appropriate vegetation/soil category. These calculations included the effects of varying receipts of solar radiation on slopes of differing orientation and steepness. Analytic procedures are detailed further in the manuscript by Nelson et al. (in review) cited below.
Active-layer matrices included here begin with July 10, and progress at weekly intervals through July 17, July 24, July 31, August 06, and end of season. The end-of-season matrix is actually for August 11, the last comprehensive measurement date. Although there was undoubtedly some further thaw during 1995, it should not have been appreciable because thawing is usually related proportionally to the square root of time.
A limited (12 spatial-temporal points) assessment of the methodology was made using thaw-depth data from the ARCSS grids for several dates during summer 1995. The results indicate that the model achieved a maximum error of 6.1 cm for average thaw depth over these 1 x 1 km areas.
Publications resulting from data in this study:
Nelson, F.E., Hinkel, K.M., Shiklomanov, N.I., Mueller, G.M., Miller, L.L., and D.A. Walker. 1998. Active-layer thickness in north-central Alaska: systematic sampling, scale and spatial autocorrelation. Journal of Geophysical Research, 103D: 28963-28973.
Nelson, F.E., Shiklomanov, N.I., Mueller, G., Hinkel, K.M., Walker, D.A., and J.G. Bockheim. 1997. Estimating active-layer thickness over a large region: Kuparuk River basin, Alaska, U.S.A. Arctic and Alpine Research, 19(4): 367-378.
Shiklomanov, N.I. and F.I. Nelson. 1999. Analytic representation of the active layer thickness field, Kuparuk River Basin, Alaska. Ecological Modelling, 123(2-3): 105-125.
Reference to Kuparuk River basin map data used in the derivation of thaw depth matrices in this dataset:
Muller, S.V., Walker, D.A., Nelson, F.E., Auerbach, N.A., Bockheim, J.G., Guyer, S., and D. Sherba. 1998. Accuracy assessment of a land-cover map of the Kuparuk River basin, Alaska: Considerations for remote regions. Photogrammetric Engineering and Remote Sensing, 64(6):619-628.