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THERMAP: Antarctic Shallow Firn Temperature Data
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Data set description paraphrased from:
Richard P. Goldthwait
USNC-IGY Antarctic Glaciological Data, Field Work 1957 and 1958
Report 825-1-Part III, August 1959
Ohio State University Research Foundation
A set of Leeds-Northrup copper-constantin thermohms was emplaced in the ice at the locality designated S-1. This site was situated
on snow-free glacier ice 5 miles from the base and at an elevation of 862 feet above sea level. The thermohms were placed
to obtain temperatures at the surface and at the following depths: 0.5, 2, 4, 11 and 16 meters. The Leeds-Northrup Wheatstone bridge,
which was used to read the thermohms, was designed so that temperatures could be read directly. Readings were taken nearly
every week beginning in February 1957 and continuing through January 1958. The area in which the thermohms were fixed was never
covered by more than 20 centimeters of snow even at mid-winter and, therefore, no attempt was made to show a change in the relative
depths of the thermohms.
Values in the following data are given in minus degrees centigrade.
Data set description paraphrased from:
John T. Hollin, Caspar Cronk and Richard Robertson
USNC-IGY Antarctic Glaciological Data, Field Work 1958 (Wilkes Station Glaciology, 1958)
Report 825-2-Part X, August 1961
Ohio State University Research Foundation
These measurements continued directly from those of 1957, and were made with the standard Leeds and Northrup bridge, switchbox and copper-constantin thermohms as used by SIPRE. Three points need comment.
(1) No stake record of the surface level at S-1 is available for the summer of 1957-58. However, at the end of the 1957 winter 20 cm of new snow covered the old ice surface in which the thermohms were originally installed. When this area was visited by the 1958 party on 27 January 1958, the surface was slush, but on 3 February 1958 had changed to ice. Since this area is normally well within the superimposed ice zone it can be safely be assumed that the 3 February ice was frozen fresh slush rather than ablated ice from a previous year. This assumption is supported by pit observations which show that the surface ice here was very coarse and bubbly and had density of only 0.76. Ice of this low density appears to last only one year, since in the following year melt water fills most of its cavities and brings the density up towards 0.9. To conclude, assuming for the 20 cm of new snow a density of 0.4, by the end of the 1957-58 summer the surface relative to the thermohms was somewhere between 0 and 8 cms higher than it was at the time of emplacement.
(2) During the 1957-58 summer the thermohms at the surface in 1957 melted its way into the ice to an unknown depth, probably less than 30 cm. Readings were, however, continued on this thermohm until its failure late in May for an unknown reason. Because of the danger of damaging the other thermohm leads it was not considered worthwhile to dig it out. Pending analysis, the few positive readings on this and the 50 cm thermohm are probably due to the absorption of radiation from the sun.
(3) In this apparatus the checkpoint, embodied in the switchbox, was a standard resistor designed to read -2.0 +/- 0.2 degrees C . In fact the reading on the checkpoint was usually out by a few tenths of a degree and on occasion by as much as 1.6 degrees C. On these occasions of large error a similar irregularity was also found in the deep thermohm readings. Temperature changes at 16m depth are clearly slow, and readings 1.6 degrees different and only one week apart are obviously incorrect. The similarity of the larger errors in both the checkpoint and the deep thermohms suggests that the cause was a bad contact at some point on the bridge side of the switchbox. For the purpose of analysis it is suggested that the 16 m temperature be plotted for the year and that deviations from it greater than the reading accuracy of 0.05 degrees C be applied as corrections to all the readings of the weeks concerned. If these corrections are made it will probably be found that most errors in the checkpoint readings then fall within approximately the 0.2 degrees C allowed by the manufacturers. Any larger errors remaining are probably the result of contact errors impossible to analyze and of very low temperatures in the resistors and wiring of the switchbox and bridge. These remaining errors can be used to calculate the limits of accuracy of the final figures.
The measurements which follow are in minus degrees centigrade, except for the few positive cases noted. Gaps in the record occur when the bridge was being used elsewhere, as on the traverse.
View Map of Wilkes Firn Temperature Site
View Table of data for 1958
