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Data Set ID:
NSIDC-0098

Firn Air Isotope and Temperature Measurements from Siple Dome and South Pole, Version 1

This data set includes d15N, d18O/2, dO2/N2/4, d40Ar/4, d38/Ar/2,
d84Kr/48, and d132Xe/96 values for air drawn from the top 15 to 50 m
of firn at the South Pole (summer and winter 1998) and a site at Siple
Dome (summers 1996 and 1998). Data also include related firn
temperature measurements.

The objective of this research was to better understand thermal
fractionation processes affecting records of atmospheric history from
firn and ice core gases. Recent work (e.g., Severinghaus and Brook,
1999) has exploited trapped air in ice and deep firn as a record of
past atmospheric composition and climate change. Interpretation of these paleoclimate archives is complicated by artifacts of thermal
diffusion, a process in which heavier gases migrate down temperature
gradients toward colder regions in the firn. Seasonal temperature
change at the snow surface creates strong temperature gradients in the
top few meters of the firn, which cause isotopic fractionation of firn
gases. A specific goal of this research is to identify any long-term
effects of seasonal temperature fluctuations on firn air isotopic
anomalies.

Geographic Coverage

Spatial Coverage:
  • N: -89.997, S: -89.997, E: -102, W: -102

  • N: -81.667, S: -81.667, E: -148.767, W: -148.767

Spatial Resolution: Not Specified
Temporal Coverage:
  • 14 January 1998 to 28 July 1998
Temporal Resolution: Not specified
Parameter(s):
  • Ice Core Records > Ice Core Air Bubbles > Firn Air
  • Glaciers/Ice Sheets > Ice Sheets > Firn Air Isotopes
  • Ice Core Records > Isotopes > Firn Air Isotopes
  • Snow/Ice > Snow/Ice Temperature > Firn Temperature
Platform(s) GROUND STATIONS, GROUND-BASED OBSERVATIONS
Sensor(s): FLASKS, MASS SPECTROMETERS, THERMISTORS
Data Format(s):
  • Microsoft Excel
  • ASCII Text
Version: V1
Data Contributor(s): Jeffrey Severinghaus, A. Grachev, Mark Battle

Data Citation

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.

Severinghaus, J. P., A. Grachev, and M. Battle. 2001. Firn Air Isotope and Temperature Measurements from Siple Dome and South Pole, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N51N7Z2P. [Date Accessed].

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Detailed Data Description

Parameter or Variable

Sample Data Record

The ASCII file "firn_air_isotopes.txt" contains gas isotope data (also available in Microsoft Excel format) and is formatted as in Table 1.

Flask ID Depth (m) δ15N δ18O/2 δO2/N2/4 δ40Ar/4 δ38Ar/2 δ84Kr/48 δ132Xe/96
Table 1. Sample Data
sdf02 0 0.0205 0.0101 0.0212 0.0133 0.0075 0.0009 0.0009
sdf03 1.55 0.0524 0.0459 0.0499 0.0279 0.0235 0.0042 0.0034
sdf05 1.55 0.0509 0.0465 0.0534 0.0283 0.023 0.0064 0.0014
sdf06 3.42 0.1216 0.1057 0.1222 0.0845 0.0728 0.0405 0.0274

An additional column header provides the estimated analytical precision of each isotopic measurement. Data are subdivided by sampling location and date. The South Pole site is located at 89.997° south latitude, 102.0°: west longitude. The Siple Dome site is located at 81.667° south latitude, 148.767° west longitude. The "shallow" and "deep" holes referred to in the table are separated by 46 m horizontally.

The ASCII file "firn_temps.txt" contains firn temperature data (also available in Microsoft Excel format) and is formatted as Table 2.

Depth (m) Firn Temperature (°C)
Table 2. Firn Temperature Data
0.1 -9.61
1.43 -19.5
2.43 -24.22
3.31 -25.78

Estimated accuracy of temperature measurements is ±0.05 C. Data are subdivided by sampling location and date.

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Software and Tools

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Data Acquisition and Processing

Investigators obtained samples using tubes inserted into boreholes. (The 18 December 1996 samples, acquired using the "bladder method" are an exception.) They extended tubes into the boreholes until their stainless steel intake screens were positioned at the desired depth. Snow and slush used to backfill the hole impeded downward movement of surface air. They pumped samples at 4 L per minute for 16 minutes to flush the tubing and sample flasks. A phosphorous pentoxide column dried the air before it was stored in 2-L flow-through glass flasks. Gas ratios were later measured by mass spectrometry at the University of Rhode Island and Scripps Institution of Oceanography (University of California, San Diego).

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References and Related Publications

Contacts and Acknowledgments

J.P. Severinghaus, Scripps Institution of Oceanography, University of California at San Diego
A. Grachev, Scripps Institution of Oceanography, University of California at San Diego
M. Battle, Bowdoin College, Brunswick, Maine

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