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Note: This data set was first published on the 1998 CAPS CD.
The text for this document was taken unchanged from that CD.

See also Description of Data Files.

The data files in this directory contain summary statistics for the thaw depth data from the CRREL site at Barrow for the years 1962-68 (1967 excluded) and 1991-93.

Active layer observations of the seasonal thaw layer at Barrow, Alaska, were started in 1962 by the U.S. Army's Cold Regions Research and Engineering Laboratory and continued into the late 1960's. Measurements were resumed in 1991 as part of an NSF funded project under the U.S. Global Change Program's Arctic System Science (ARCSS) Land-Atmosphere-Ice Interactions (LAII) program. Data collection was the responsibility of Jerry Brown at CRREL. Data compilation and reduction for the ARCSS/LAII program, funded by the U.S. National Science Foundation, was supervised by Frederick Nelson, Department of Geography and Planning, State University of New York at Albany.

Active Layer thickness (thaw depth) measurements at Barrow, Alaska, include weekly and seasonal probing of the shallow active layer using a metal probe to the point of refusal.

In 1962, 10 x 10 meter plots were randomly distributed across a 2-km long transect characteristic of the ice-wedge dominated Arctic Coastal Plain. Plots were subdivided into 2 x 2 m squares and the active layer measured at 20 border points during the thaw season, and at all 36 grid points in late August and/or early September. Data from a total of 42 plots are available at variable sampling intervals, with a standard set of 20 plots at the end of the thaw season (400 points per sample date). Summary and descriptive statistics for each plot on each date of measurement are reported in the data sets contained within subdirectories in this directory.

Summary statistics by plot are believed to be accurate reflections of the position of the seasonal thawing front, owing to the ice-bonded nature of the substrate and the number of replications at each plot. Values reflecting observations made in late summer and early fall may be slightly greater than actual (thermally defined) thaw depth values because some refreezing may have occurred from the bottom of the active layer.

The newly frozen basal layer may be too weakly bonded to provide adequate resistance to probing in such cases, resulting in slight overestimates of the true depth of thaw.

Subdirectories in this directory correspond to data-collection years; within each subdirectory are many files, each of which corresponds to one of the original CRREL observation plots at Barrow (i.e., the directory /1964 contains all of the data collected in the year 1964, one file per plot). Each file contains statistical descriptions, arranged sequentially, on each date that measurements were made at each site. In the directory /1964, the file 64PL16.DAT contains data for plot number 16 for the year 1964. The first row contains the date at which sampling took place. The date '640701' refers to a sampling date of 1 July, 1964 (data from the year 1962 have no day date associated with them: therefore, the date listed as 620800 is read as August 1962). The second row specifies the plot number from which the statistics were derived. The third row specifies the number of test cases used to calculate the statistics. The next 12 rows show the statistics generated at the plot number specified for a particular date. The following is a partial sample of a typical data set in this collection:

The following table shows the number of days that samples were taken in a year and the number of columns in a file for a particular year:

A template was used to construct the files for each year (based on dates that sampling took place), so many of the files show "no data" on one or more dates. Not all sites were sampled on every measurement date. The data were organized in this way to help the user track the progression of thaw depth at individual sites over the course of a summer season.

ANALYSIS:

This incomplete time series of active layer measurements provides valuable insight into the response of permafrost terrain to seasonal climate fluctuations. Up to the present, warmer summers have not produced increased depth of the active layer at Barrow. A shallower active layer has been observed in the 1990's data, compared to those from the 1960's.

CONTACT INFORMATION:

Further questions and requests for information about this data set may be forwarded to Frederick Nelson, Department of Geography and Planning, State University of New York at Albany, Albany, NY 12222. Phone: (518) 442-4770. FAX: (518) 442-4867. Internet: fnelson@uacsc1.albany.edu.

REFERENCES:

Brown, Jerry and Johnson, P.L. 1965. Pedo-ecological Investigations, Barrow, Alaska. Cold Regions Research and Engineering Laboratory Technical Report 159, Hanover, NH, 32 pages plus appendices.

Brown, Jerry 1969. Soil properties developed on the complex tundra relief of northern Alaska. Biuletyn Peryglacjalny, vol. 18, pp. 153-167.

Mc Gaw, R. W., Outcalt, S.I., and Ng, E. 1978. Thermal properties and regime of wet tundra soils at Barrow, Alaska. In Proceedings, Third International Conference on Permafrost, National Research Council of Canada, Ottawa, Canada, vol. 1, 47-53.

Nakano,Y.,and Brown,J. 1972. Mathematical modelling and validation of the thermal regimes in tundra soils, Barrow, Alaska. Arctic and Alpine Research, 4: 19-38.

National Science Foundation Grant OPP 9214897; Active Layer/Landscape Interactions: A Retrospective and Contemporary Regional Approach in Arctic Alaska. Ohio State University.