This data set is comprised of four surveyed valleys focusing on the depth to ground ice in the high-elevation Quartermain Mountains in the Beacon Valley area: University Valley, Farnell Valley, and two unnamed valleys north of University Valley, which we will call Valley North and Valley 2 North. To date it is only in the high-elevation Dry Valleys that the climatic conditions are dry and cold enough that cryotic (always below 0°C) yet dry soil is found over ice-cemented ground (McKay et al. 1998); (Bockheim 2007). The data provide a qualitative and quantitative contribution towards understanding the type and distribution of ground ice in the Quartermain Mountains at a high spatial resolution. The measurements can be used to improve and validate models of ice stability and distribution. This data set contains observations of depth to ice-cemented ground, based on 475 measurements at 147 sites. Note that the measurements represent the thickness of the active layer plus any dry permafrost layer, which is ubiquitous in this region, and not just the thickness of the active layer.
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Depths to Ice-cemented Soils in High-elevation Quartermain Mountains, Dry Valleys, Antarctica, Version 1
|Spatial Resolution:||Not Specified|
|Temporal Resolution:||Not specified|
|Data Contributor(s):||Margarita Marinova, Christopher McKay|
|Metadata XML:||View Metadata Record|
As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.McKay, C. P. and M. M. Marinova. 2013. Depths to Ice-cemented Soils in High-elevation Quartermain Mountains, Dry Valleys, Antarctica, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N5VX0DFJ. [Date Accessed].
Detailed Data Description
The data contain all depth to ice-cemented ground measurements made for the four valleys mapped: Farnell Valley, University Valley, Valley North, and Valley 2 North (two unnamed valleys to the north of University Valley). The depths to ice-cemented ground measured in each valley are in a separate CSV file. See the File and Directory Structure section for more information on the various files that make up this data set. Importantly, a different number of measurements per site were made, and not every method of probing the subsurface was utilized at each site. Thus, the headers provide the necessary information for each file.
The number of total measurements, and the methods by which the measurements were taken, vary for each location. If a given method is not reported on, then it was not used. The reported averages are based on all of the data since no method of measurement was weighted differently. Same for the calculated standard deviation. In cases where we could not reach the ice-cemented ground, a mean "deeper than" value is still calculated, but no standard deviation is given.
The reported distance is given from where the edge of the snow pack was when there was a snow pack/glacier at the head of the valley, or otherwise from where the valley floor seemed to start at the head of the valley, which is subjective. All values of -999 should be disregarded since they were used as filler values since each site had a different number of measurement.
Data are provided in Comma-Separated Values (CSV).
Data are available on the FTP site in the
ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0529_mckay_V01 directory. Within this directory, there are four files:
|File Name||File Size|
The entire data set is approximately 19 KB.
Southernmost Latitude: 77° 50' S
Northernmost Latitude: 77° 54' S
Westernmost Longitude: 160° 40' E
Easternmost Longitude: 160° 49' E
High-elevation Quartermain Mountains: Farnell Valley, University Valley, Valley North, and Valley 2 North (two unnamed valleys to the north). The data file gives exact lattitude and longitude measurements for each site.
The typical distance between sites within each valley was 50 - 200 m. The transects were started at the head of the valleys, and sample site spacing was kept constant with the distance between consecutive sites either 50, 100, or 200 m apart, depending on the valley and the meteorological conditions at the time.
These data were collected from 30 September 2009 to 15 December 2010.
This data set contains the following parameters:
Active Layer Observations
Active Layer Thickness
Depth to Ice-Cemented Ground
Measurements are depths to ice-cemented ground. Note that this does not represent the depth of the active layer, as dry permafrost is present in these regions. The measurements thus show the thickness of the active layer plus any dry permafrost at the location of measurement.
Sample Data Record
The following sample data record is of the
Valley2North data file.
Data Acquisition and Processing
The observations of depth to ice-cemented ground which are reported here are based on 475 measurements at 147 sites: 3 - 5 measurements were taken at each site over a c. 1 m2 area and were averaged. The measurements were made during the first two weeks of December 2009 and December 2010. There were 36 sites in Farnell Valley, 68 in University Valley, 27 in Valley North, and 16 in Valley 2 North. The typical distance between sites within each valley was 50 - 200 m. The transects were started at the head of the valleys, and sample site spacing was kept constant with the distance between consecutive sites either 50, 100, or 200 m apart, depending on the valley and the meteorological conditions at the time. This approach ensures an even distribution of sample sites and minimized bias related to soil type and geomorphology. Sample locations were recorded to an accuracy of ±3 m using a Garmin 60CSx GPS. Refer to Figure 1 for a map of Beacon Valley and the smaller, overhanging valleys. Overlain are the mapped sites and measured depths to ground ice in Farnell Valley (southernmost), University Valley, and the two unnamed valleys north of University Valley: Valley North and Valley 2 North.
Polygonal ground was present in all four valleys and since the depth to ice-cemented ground is known to be disrupted in polygon troughs, the measurements were standardized by choosing a flat area near the center of the polygon. The depth to ground ice was determined by either digging a soil pit, using an active layer probe (sharpened metal rod), or drilling until the ice-cemented ground interface was reached. Soil pits readily confirmed the presence of ice-cemented ground, probe depths were based on resistance, and drill depths were based on the presence of ice in drill cuttings. Field observations of soil pits at drilling sites confirmed that drilling was a reliable method for determining the depth to ice-cemented ground. The least reliable method was the active layer probe, as the presence of subsurface rocks could confound this method. Whenever there was any doubt, such as greater-than-expected variability between measurements, a soil pit was dug.
Drilling proved to be the most efficient and accurate method. We used a Hilti drill with a ½ inch diameter and a 1 m long drill string. The operator could tell when the drill reached ice-cemented ground due to the change in pressure required to advance the drill and changes in the frequency of vibrations during drilling. At this point, a magnet was placed at ground level on the drill string, and the drill was retrieved to confirm that ice was present at the tip of the string, and the distance between the magnet and the tip of the drill string was measured.
At some sites the ice-cemented ground could not be reached. These locations are identified with empty symbols. Refer to Figure 1. Ideally, probing to about 3 m would have provided a definitive result as to whether ice-cemented ground is at all present at a location, based on thermal and vapour pressure models (McKay 2009). As a test of McKay's (2009) proposed stability zone, we report cases where the depth to ice-cemented ground is deeper than could be measured.
Figure 2 shows the depth to ground ice and linear fits for all four valleys:
- Farnell Valley: slope of linear fit = -9 cm km-1, normRMS = 16.9%, P-value 0.001, 26 9% increase in RMS if no change in depth is prescribed.
- University Valley: slope = -32 cm km-1, normRMS = 11.5%, P-value 10-15, 77% RMS increase if constant depth prescribed.
- Valley North: slope = -10 cm km-1, normRMS = 25.0%, P-value 0.31, 2% RMS increase if constant depth.
- Valley 2 North: slope = -11 cm km-1, normRMS = 18.5%, P-value 0.22, 6% RMS increase if constant depth, respectively.
The distance is measured from the head of the valley or the edge of the glacier/snowpack at the head of the valley. In each panel shown in Figure 2, the circles represent the northernmost transect in the given valley, up triangles are the next transect to the south in the same valley, and squares are the next further south transect, which are only available for University Valley. Empty symbols represent locations where the ground was probed to the given depth but no ice-cemented ground was reached, for example the ice is deeper than the indicated depth. These measurements are not included in the fits. Two data points from Dickinson & Hopkins (2005) for University Valley are plotted as empty down triangles at 500 and 1260 m distance, and are consistent with our data; these data are not included in the fits.
The precision of measurement for all methods is a couple of centimeters due to the need to drill into the ice and the difficulty of defining the reference surface plane in environments with significant surface roughness. The measured depth to ice-cemented ground is generally insensitive to the time of year during which the measurement is taken since modeled ice evaporation rates, for example seasonal depth of ice-cemented ground fluctuations, are 0.2- 0.5 mm per year (McKay et al. 1998); (Liu et al. 2011), and these changes are significantly smaller than our measurement error. In measuring the depth to ice-cemented ground, annual and seasonal temperature variations are important only when the soil is water saturated to the surface. When a dry permafrost layer is present, seasonal and yearly variations in temperature will only affect the depth to the top of the dry permafrost layer but not the depth of the ice-cemented layer.
References and Related Publications
Contacts and Acknowledgments
Dr. Chris McKay
NASA Ames Research Center
Space Science Division
Moffett Field, CA 94035
Dr. Margarita Marinova
Bay Area Environmental Research Institute
Sonoma, CA 95476
This research was supported by NSF OPP Grant Number 811073.02.10.02.31 and the NASA ASTEP program.
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