Carbon-14 Measurements in Atmospheric CO₂ from Northern and Southern Hemisphere Sites, 1962-1993

PDF File    Digital Data (NDP-057)

Contributed by

Reidar Nydal and Knut Lövseth
Radiological Dating Laboratory
The Norwegian Institute of Technology
Trondheim, Norway

Prepared by

Virgene Zumbrunn^* and Thomas A. Boden
Carbon Dioxide Information Analysis Center
World Data Center-A for Atmospheric Trace Gases
Oak Ridge National Laboratory
Oak Ridge, Tennessee

*ORISE summer intern

Environmental Sciences Division Publication No. 4582

Date Published: November 1996

Prepared for the
Global Change Research Program
Environmental Sciences Division
Office of Health and Environmental Research
U.S. Department of Energy
Budget Activity Number KP 05 02 00 0

Prepared by the
Carbon Dioxide Information Analysis Center
World Data Center-A for Atmospheric Trace Gases
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37831-6290
managed by
LOCKHEED MARTIN ENERGY RESEARCH CORP.
for the
U.S. DEPARTMENT OF ENERGY
under contract DE-AC05-96OR22464

DOI

10.3334/CDIAC/atg.ndp057

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CONTENTS

LIST OF FIGURES

LIST OF TABLES

ABSTRACT

PART 1: OVERVIEW

1. NAME OF THE NUMERIC DATA PACKAGE
2. PRINCIPAL INVESTIGATORS
3. KEYWORDS
4. BACKGROUND INFORMATION
5. SAMPLING AND CALCULATION
6. APPLICATIONS OF THE DATA
7. DATA LIMITATIONS AND RESTRICTIONS
8. REFERENCES
9. DATA-PROCESSING ACTIVITIES AND QUALITY ASSURANCE CHECKS PERFORMED BY CDIAC
10. HOW TO OBTAIN THE DATA AND DOCUMENTATION

PART 2: CONTENT AND FORMAT OF DATA FILES

11. LISTING OF FILES PROVIDED
12. FILE DESCRIPTIONS
13. LISTING OF THE FORTRAN 77 DATA RETRIEVAL PROGRAMS
14. LISTING OF THE SAS^® DATA RETRIEVAL PROGRAMS
15. PARTIAL LISTINGS OF DATA FILES
16. VERIFICATION OF DATA TRANSPORT

APPENDIX A. FIGURES SHOWING TROPOSPHERIC AND STRATOSPHERIC

¹⁴C MEASUREMENTS IN ATMOSPHERIC CO₂ FROM 14 NORTHERN

AND SOUTHERN HEMISPHERE SITES

APPENDIX B. REPRINT OF PERTINENT LITERATURE

Tracing Bomb ¹⁴C in the Atmosphere 1962-1980, by R. Nydal and K. Lövseth. 1983.

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LIST OF FIGURES

1. Sampling network for tropospheric ¹⁴C measurements in atmospheric CO₂

2. Corrected ¹⁴C measurements from air samples collected at five Norwegian sites from 1963 to 1970

A-1. Corrected ¹⁴C measurements from air samples collected at Kapp Linné, Fruholmen, Gråkallen,

and Vassfjellet

A-2. Corrected ¹⁴C measurements from air samples collected at Lindesnes, Norway; Santiago

de Compostela, Spain;and Rehovot, Israel

A-3. Corrected ¹⁴C measurements from air samples collected at Izaña, Canary Islands; Mas Palomas,

Grand CanaryIsland; Dakar, Senegal; Dakar-Fann, Senegal; and N'Djamena, Chad

A-4. Corrected ¹⁴C measurements from air samples collected at Debre Zeit, Ethiopia; Fianarantsoa,

Madagascar; and by aircraft flying in the low stratosphere above Trondheim, Norway

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LIST OF TABLES

1. Summary of the tropospheric ¹⁴CO₂ sampling sites

2. Characteristics of numeric variables in the file containing carbon isotope data from all 14 sampling locations

3. Characteristics of numeric variables in the file containing stratospheric carbon isotope data derived from

air samples collected by aircraft during 1965

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ABSTRACT

Nydal, R., and K. Lövseth. 1996. Carbon-14 Measurements in Atmospheric CO₂ from Northern and Southern Hemisphere Sites, 1962-1993. ORNL/CDIAC-93, NDP-057. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee. 67 pp. doi: 10.3334/CDIAC/atg.ndp057

In the 1960s, thermonuclear bomb tests released significant pulses of radioactive ¹⁴C into the atmosphere. This major perturbation allowed scientists to study the dynamics of the global carbon cycle by measuring and observing rates of isotopic exchange. The Radiological Dating Laboratory at the Norwegian Institute of Technology performed ¹⁴C measurements in atmospheric CO₂ from 1962 to 1993 at a network of ground stations in the Northern and Southern hemispheres. These measurements were supplemented during 1965 with high-altitude (9-12.6 km) air samples collected using aircraft from the Norwegian Air Force. The resulting database, coupled with other ¹⁴C data sets, provides a greater understanding of the dynamic carbon reservoir and a crude picture of anomalous sources and sinks at different geographical latitudes. This database is outstanding for its inclusion of early ¹⁴C measurements, broad spatial coverage of sampling, consistency of sampling method, and Δ¹⁴C calculation results corrected for isotopic fractionation and radioactive decay. This database replaces previous versions published by the authors and the Radiological Dating Laboratory.

Fourteen stations spanning latitudes from Spitsbergen (78°N) to Madagascar (21°S) were used for sampling during the lifetime of the Norwegian program. Some of the stations have data for only a brief period, while others have measurements through 1993. Sampling stations subject to local industrial CO₂ contamination were avoided. The sites have sufficient separation to describe the latitudinal distribution of ¹⁴C in atmospheric models. The sampling procedure for all the surface (10-2400 m asl) ¹⁴C measurements in this database consisted of quantitative absorption of atmospheric CO₂ in carbonate-free 0.5 N NaOH solution. The ¹⁴C measurements were made in a CO₂ proportional counter and calculated (δ¹⁴C) as per mil excess above the normal ¹⁴C level defined by the US National Institute of Standards and Technology (NIST). Atmospheric ¹⁴C content is finally expressed as Δ¹⁴C, which is the relative deviation of the measured ¹⁴C activity from the NIST oxalic acid standard activity, after correction for isotopic fractionation and radioactive decay related to age. The data are organized by sampling station, and each record of the database contains the sampling dates; values for ¹⁴C excess (δ¹⁴C) relative to the NIST standard, fractionation ¹³C (δ¹³C) relative to the Pee Dee Belemnite (PDB) standard, and corrected ¹⁴C (Δ¹⁴C) excess; and the standard deviation for Δ¹⁴C. The Δ¹⁴C calculation results presented here are thus corrected for isotopic fractionation and radioactive decay, and constitute the final product of a research effort that has spanned three decades.

The Δ¹⁴C station data show a sharp increase in tropospheric radiocarbon levels in the early 1960s and then a decline after the majority of nuclear tests came to an end on August 5, 1963 (Test Ban Treaty). The sharp peaks in tropospheric radiocarbon in the early 1960s are more pronounced in the Northern Hemisphere, reflecting the location of most atomic weapons tests. The measurements show large seasonal variations in the Δ¹⁴C level during the early 1960s mainly as a result of springtime transport of bomb Δ¹⁴C from the stratosphere. During the 1970s, the seasonal variations are smaller and due partly to seasonal variations in CO₂ from fossil-fuel emissions. The rate of decrease of atmospheric radiocarbon provides a check on the exchange constants of the atmosphere and ocean.

This report and all data it describes are available from the Carbon Dioxide Information Analysis Center (CDIAC) without charge. The Nydal and Lövseth atmospheric ¹⁴C database comprises 21 data files totaling 0.2 megabytes in size. The following report describes the sampling methods and analysis. In addition, the report includes a complete discussion of CDIAC's data-processing efforts, the contents and format of the data files, and a reprint of a Nydal and Lövseth journal article.

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PART 1: OVERVIEW

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1. NAME OF THE NUMERIC DATA PACKAGE

Carbon-14 Measurements in Atmospheric CO₂ from Northern and Southern Hemisphere Sites, 1962-1993

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2. PRINCIPAL INVESTIGATORS

Reidar Nydal and Knut Lövseth
Radiological Dating Laboratory
The Norwegian Institute of Technology
Trondheim, Norway

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3. KEYWORDS

Radiocarbon, ¹⁴C, atmospheric CO₂, quantitative NaOH absorption, carbon isotopes, bomb ¹⁴C, Δ¹⁴C, δ¹⁴C, δ¹³C, troposphere, stratosphere, aircraft sampling

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4. BACKGROUND INFORMATION

Atmospheric carbon dioxide (CO₂) contains, besides ¹²C (~99%), small amounts of the carbon isotopes ¹³C and ¹⁴C. Only ¹⁴C is radioactive with a half-life of 5730 years. In the atmosphere, ¹⁴C occurs principally as ¹⁴CO₂ and is usually produced by nuclear reactions between cosmic ray neutrons and the nitrogen atoms of the air (Libby 1952). Solar (heliomagnetic), geomagnetic, and ocean forcing all play a role in atmospheric ¹⁴CO₂ (Stuiver and Braziunas 1993). Before nuclear bomb testing during the 1950s and early 1960s, radiocarbon levels in the atmosphere had been in decline. Suess (1955) demonstrated that forests grown between 1930 and 1950 had Δ¹⁴C values 20-40 per mil below those of pre-1890 woods as a result of anthropogenic ¹⁴C-free CO₂ emissions since the Industrial Revolution. Nuclear bomb testing has since swamped the "Suess Effect⁽¹⁾." After a series of atomic weapons tests were conducted at higher northern latitudes, notably Novaya Zemlya in the former Soviet Union, scientists at the Radiological Dating Laboratory in Norway seized the opportunity to conduct CO₂ sampling to trace the distribution and flux of bomb ¹⁴C with funding support from the Norwegian Research Council. In the early 1960s, several ground sampling sites were established in Norway. These Norwegian study sites gradually expanded to a global network of 14 stations spanning latitudes from Spitsbergen (78°N) to Madagascar (21°S) (Fig. 1; Table 1). Sites possibly contaminated by local CO₂ sources were avoided. Additional sites were chosen to improve spatial coverage so that the distribution of radiocarbon could be characterized with respect to latitude. During 1965 the ground-level measurements were supplemented with measurements made on air samples collected from the lower stratosphere (9000-12600 m) using aircraft from the Norwegian Air Force. This data document provides the surface ¹⁴C measurements made by the Radiological Dating Laboratory at this global sampling network and the high-altitude measurements made during 1965. The Δ¹⁴C data presented here are corrected for isotopic fractionation and radioactive decay, and constitute the final product of a research effort that has spanned three decades. The earliest measurements date back to 1962, and a few sites have data through 1993. Earlier versions of this database have been presented by Nydal (1966, 1968, 1993), Nydal and Lövseth (1983), and Nydal et al. (1971).

1. The relative change in the 14C or 13C ratio of any carbon pool or reservoir caused by the addition of fossil-fuel CO2 to the atmosphere. Fossil fuels are devoid of 14C because of the radioactive decay of 14C to 14N during long underground storage and are depleted in 13C because of isotopic fractionation long ago during photosynthesis by the plants that were the precursors of the fossil fuels. Carbon dioxide produced by the combustion of fossil fuels is thus virtually free of 14C and depleted in 13C. The term "Suess Effect" originally referred to the dilution of the 14C/C ratio in atmospheric CO2 but the definition has been extended to both the 14C and 13C ratios in any pool or reservoir of the carbon cycle resulting from human disturbances (Keeling 1979).

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5. SAMPLING AND CALCULATION

All ground-level air samples represented in this database were collected by dynamic quantitative absorption of atmospheric CO₂ in carbonate-free 0.5 N sodium hydroxide (NaOH) solution. During the collection process, a dish of NaOH was exposed to the air for 4 to 7 days. Following exposure, the samples were treated with hydrochloric acid to regenerate the carbon dioxide. After a purification procedure, the CO₂ was analyzed in a proportional counter to assess ¹⁴C content. Typically, a counter has gas volumes of 1-2 L and operates at 2 atm pressure. Until 1981 a counting time of 2 days (48 hours) was often used (Nydal and Lövseth 1983), but a counting time of 4 days was used later in order to obtain higher precision.

High-altitude samples were collected in the Trondheim area during 1965 using aircraft from the Norwegian Air Force. Flights originated from Örlandet Airport and covered a region bounded by 62-65°N and 6-10°E, at altitudes of 9000-12600 m. Samples were collected using a filter with a 1.4 kg molecular sieve that absorbs CO₂ from the penetrating air. The filter container was placed under the wing of the plane and opened and closed with electrically-operated shutters at both ends. With the plane traveling at a speed of approximately 900 km/hr the filter shutters were opened 15 minutes to allow sufficient amounts of CO₂ to be absorbed.

After determination of the ¹⁴C content in a proportional counter, the δ¹⁴C values were calculated as per mil excess above the normal ¹⁴C level defined by the National Institute of Standards and Technology (NIST, formerly the US National Bureau of Standards). Atmospheric ¹⁴C content is finally expressed as Δ¹⁴C, which is the relative deviation of the measured ¹⁴C activity from the NIST oxalic acid standard activity, after correction for isotopic mass fractionation and radioactive decay related to age (Stuiver and Polach 1977). Δ¹⁴C is expressed in per mil (not as a percentage) and calculated using the following two steps:

Δ14 = δ14C - 2(δ13C + 25)(1 + δ14C/1000)	(1)
Δ14C = Δ14 + 1000(e λ (1950-t) - 1)	(2)

In step 1, the ¹⁴C excess (Δ¹⁴) is only corrected for isotopic mass fractionation. δ¹⁴C represents the uncorrected (for decay) ¹⁴C relative to the NIST standard and δ¹³C represents the deviation in the ¹³C/¹²C ratio relative to the Pee Dee Belemnite (Pee Dee River, South Carolina) standard. The ¹³C/¹²C ratio was measured by mass spectrometry. By themselves, the δ¹³C values represent data that are highly influenced by fractionation in NaOH in the absorbing dish. In the earlier presentation of the ¹⁴C data from the Radiological Dating Laboratory only step 1 was used, and the decay of the NIST ¹⁴C reference standard after 1950 was not taken into account (Nydal and Lövseth 1983). Applying the approximate formula in step 2, where λ is 1/8267 years (T/ln2 where T is the 5730 year half-life of ¹⁴C) and t is the year of sampling, this small decay (2-5 per mil) has now been applied to all the Δ¹⁴C data appearing in this database.

For a further discussion of the sampling methods and each sampling site, please see the reprint of Nydal and Lövseth (1983) in Appendix B. For additional information on the high-altitude sampling, see Hagemann et al. (1965), Nydal (1966), and Nydal and Lövseth (1983). For additional information on the sampling sites, radiocarbon standards, and carbon isotope measurements, see Nydal (1966, 1968), Craig (1961), and Levin et al. (1980).

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6. APPLICATIONS OF THE DATA

These measurements were originally made to assess potential human health risks from radioactive fallout in the atmosphere. Fortunately it was also recognized that the radioactive isotopes already injected into the atmosphere could be useful tracers in geophysical research. These ¹⁴C measurements document the time lag of isotopic sea-air exchange and chronicle a long-term decline in Δ¹⁴CO₂ at Northern and Southern hemisphere sites. These measurements complement other radiocarbon data sets (Broecker and Olson 1959; Levin et al. 1985, 1995; Manning et al. 1990; Olsson 1993) and support the pronounced twentieth-century Δ¹⁴C reduction reported by Stuiver and Quay (1981) due to ¹⁴C-free carbon dioxide released by fossil-fuel combustion.

This data set is unique for its inclusion of measurements in the early 1960s that trace the bomb ¹⁴C released by a series of nuclear tests. All measurements at the global network of sites were taken by dynamic quantitative absorption of CO₂ in NaOH solution. This consistency in sampling technique over a period of three decades is valuable to researchers and modelers.

The Δ¹⁴C tropospheric data show a sharp increase in tropospheric radiocarbon levels in the early 1960s and then a decline after the majority of nuclear tests came to an end on August 5, 1963 through the Test Ban Treaty. The sharp peaks in tropospheric radiocarbon in the early 1960s are more pronounced in the Northern Hemisphere, reflecting the location of most atomic weapons tests. The measurements show large seasonal variations in the Δ¹⁴C level in the early 1960s, mainly as a result of springtime transport of bomb ¹⁴C from the stratosphere (Fig. 2). During the 1970s, the seasonal variations are smaller and are partly due to seasonal variations in CO₂ from fossil-fuel emissions. The rate of decrease of atmospheric radiocarbon provides a check on the exchange constants of the atmosphere and ocean.

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7. DATA LIMITATIONS AND RESTRICTIONS

Please note that the δ¹³C values provided in this database are not representative of atmospheric values. In this database the ¹³C data serve as guides to the ¹⁴C measurements and were used to calculate corrected ¹⁴C. It should also be noted that the ¹³C/C¹² ratio was not measured for every sample. In these instances where the ¹³C/C¹² ratio was not measured, a mean value is given for δ¹³C and identified by a flag code. These mean values were calculated from 20-40 ground-level measurements or 4 high-altitude measurements.

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8. REFERENCES

• Broecker, W. S., and E. A. Olson. 1959. Lamont Radiocarbon Measurements VI*. American Journal of Science Radiocarbon Supplement 1:111-32.
• Craig, H. 1961. Mass-spectrometer analyses of radiocarbon standards. Radiocarbon 3:1-3.
• Hagemann, F.T., J. Gray, Jr., and L. Machta. 1965. Carbon 14 measurements in the atmosphere - 1953 to 1964. U.S. Atomic Energy Commission Report. HASL-159, 124 pgs.
• Keeling, C.D. 1979. The Suess Effect: ¹³Carbon-¹⁴Carbon Interrelations. Environment International 2:229-300.
• Levin, I., K. O. Münnich, and W. Weiss. 1980. The effect of anthropogenic CO₂ and ¹⁴C sources on the distribution of ¹⁴C in the atmosphere. Radiocarbon 22:379-91.
• Levin, I., B. Kromer, H. Schoch-Fischer, M. Bruns, M. Münnich, D. Berdau, J. C. Vogel, and K. O. Münnich. 1985. 25 years of tropospheric ¹⁴C observations in central Europe. Radiocarbon 27(1)1-19.
• Levin, I., R. Graul, and N. B. A. Trivett. 1995. Long-term observations of atmospheric CO₂ and carbon isotopes at continental sites in Germany. Tellus 47(B):23-34.
• Libby, W.F. 1952. Radiocarbon dating. The University of Chicago Press, Chicago, Illinois, USA 161 pgs.
• Manning, M. R., D. C. Lowe, W. H. Melhuish, R. J. Sparks, G. Wallace, C. A. M. Brenninkmeijer, and R. C. McGill. 1990. The use of radiocarbon measurements in atmospheric studies. Radiocarbon 32(1):37-58.
• Nydal, R. 1966. Variation in C¹⁴ concentration in the atmosphere during the last several years. Tellus 18:271-79.
• Nydal, R. 1968. Further investigation on the transfer of radiocarbon in nature. Journal of Geophysical Research 73:3617-35.
• Nydal, R. 1993. Application of bomb ¹⁴C as a tracer in the global carbon cycle. Trends in Geophysical Research 2:355-64.
• Nydal, R., and K. Lövseth. 1983. Tracing bomb ¹⁴C in the atmosphere, 1962-1980. Journal of Geophysical Research 88:3621-42.
• Nydal, R., K. Lövseth, and O. Syrstad. 1971. Bomb ¹⁴C in the human population. Nature 232:418-21.
• Olsson, I. U. 1993. A ten-year record of different levels of the ¹⁴C activities over Sweden and the Arctic. Tellus 45(B):479-81.
• Stuiver, M., and H. A. Polach. 1977. Discussion: Reporting of ¹⁴C data. Radiocarbon 19:355-63.
• Stuiver, M., and P. D. Quay. 1981. Atmospheric ¹⁴C changes resulting from fossil fuel CO₂ release and cosmic ray flux variability. Earth and Planetary Science Letters 53:349-62.
• Stuiver, M., and T. F. Braziunas. 1993. Sun, ocean, climate and atmospheric ¹⁴CO₂: An evaluation of causal and spectral relationships. The Holocene 3(4):289-305.
• Suess, H. E. 1955. Radiocarbon concentration in modern wood. Science 122:415-17.

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9. DATA-PROCESSING ACTIVITIES AND QUALITY ASSURANCE CHECKS PERFORMED BY CDIAC

CDIAC is committed to the quality assurance (QA) of data before distribution. In order to provide scientists and researchers with high-quality data, CDIAC reviews the data it receives for consistent formatting, completeness, reasonableness, and accuracy. Each review involvesprogramming that is specific to the needs of each data set. These efforts are indicative of CDIAC's mission to provide the international scientific community with high-quality, well-documented data.

DATA-PROCESSING

CDIAC obtained the Nydal and Lövseth database as an electronic-mail message from Reidar Nydal. CDIAC staff edited the message and created the ASCII data files for each site. Working copies of the files were created and processed in the following ways:

1. The original ASCII files were reformatted into a consistent format and combined in a single file with data from all sites.

2. Both SAS^® and FORTRAN 77 codes were written and are available to the user for reading any of the ASCII data files.

QA CHECKS

1. Each file was checked to ensure formatting consistency and to confirm the absence of missing data entries.

2. Checks were performed to confirm the uniqueness of each laboratory reference code and to ensure that sampling intervals were formatted consistently.

3. Mean, minimum, and maximum values for δ¹⁴C, δ¹³C, and corrected Δ¹⁴C data at each site were calculated and assessed for reasonableness.

4. All δ¹⁴C, δ¹³C, and corrected Δ¹⁴C measurements were plotted and assessed for reasonableness.

5. Any inconsistencies or suspect measurements were reported to and addressed by the investigators before the data set was released.

SAS^® is the registered trademark of SAS Institute, Inc., Cary, North Carolina, 27511, USA.

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10. HOW TO OBTAIN THE DATA AND DOCUMENTATION

The Nydal and Lövseth database is available in machine-readable form from CDIAC without charge. The database may also be downloaded from CDIAC's anonymous File Transfer Protocol (FTP) site, by using the address, login instructions, and FTP commands listed below. In addition, the database is available on 9-track magnetic tape, 8-mm tape, or IBM- or Macintosh-formatted floppy diskettes. For tape requests, please include preferred tape specifications (i.e., 1600 or 6250 BPI for 9-track tapes and 8200 or 8500 format for 8-mm tapes, labeled or nonlabeled, ASCII or EBCDIC characters, variable or fixed-record lengths). Requests without tape specifications will be filled on 9-track, 6250 BPI, nonlabeled tapes with file attributes shown in Sect. 11.

This documentation is available only from CDIAC. Electronic versions of the documentation are available via the World Wide Web from CDIAC's home page (http://cdiac.esd.ornl.gov). Requests for printed copies of the documentation should be addressed to

Carbon Dioxide Information Analysis Center
World Data Center-A for Atmospheric Trace Gases
Oak Ridge National Laboratory
Post Office Box 2008
Oak Ridge, TN 37831-6290, USA

The tapes, diskettes, and documentation may also be ordered by telephone, facsimile, or electronic mail:

Telephone: (865) 574-3645 or (865) 574-0390
Fax: (865) 574-2232
Electronic mail: cdiac@ornl.gov

FTP access: ftp cdiac.esd.ornl.gov (or 128.219.24.36) Enter anonymous at the userid prompt
Enter your e-mail address as the password
Change the directory to /pub/ndp057 (i.e., ftp> cd /pub/ndp057)
Retrieve all files (i.e., ftp> mget *)

NOTE: When using these radiocarbon data in a presentation or publication, PLEASE acknowledge the principal investigators, Reidar Nydal and Knut Lövseth, and the Norwegian Institute of Technology!

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PART 2: CONTENT AND FORMAT OF DATA FILES

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11. LISTING OF FILES PROVIDED

The following is a list of the files that compose the Nydal and Lövseth atmospheric carbon isotope database and that are distributed by CDIAC along with this documentation. These files are available on a variety of media (see Sect. 10, "How To Obtain the Data and Documentation"). This listing has been tailored to reflect a 9-track magnetic tape request. The record formats, block sizes, and record lengths shown are the defaults for those not specifying these parameters when requesting machine-readable data files on 9-track magnetic tape. The default tape density, labeling, and characters are 6250 BPI, nonlabeled, and ASCII, respectively.

^aFixed-block record format.
^®SAS is the registered trademark of SAS Institute, Inc., Cary, North Carolina, 27511, USA.

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12. FILE DESCRIPTIONS

This section describes the content and format of each of the 21 files that compose this numeric data package (NDP) and the Nydal and Lövseth atmospheric carbon isotope database.

DATA FILES

This NDP consists of the following 21 files:

• a descriptive file that contains an overview of the Nydal and Lövseth atmospheric carbon isotope database and detailed descriptions of the data files (ndp057.doc);
• one FORTRAN 77 data retrieval routine to read and print any of the 15 data files containing estimates of δ¹⁴C, δ¹³C, and Δ¹⁴C in atmospheric CO₂ from air samples collected at 14 sites (ndp057.for);
• one SAS^® data retrieval routine to read and print any of the 15 data files (ndp057.sas);
• one ASCII data file containing estimates of δ¹⁴C, δ¹³C, and Δ¹⁴C in atmospheric CO₂ from all 14 sites (nydal.asc);
• 14 ASCII data files (one for each sampling location) containing estimates of δ¹⁴C, δ¹³C, and Δ¹⁴C in atmospheric CO₂ (**.asc -- see description of "LABREF" on page 15),
• one FORTRAN 77 data retrieval routine to read and print the file containing estimates of δ¹⁴C, δ¹³C, and Δ¹⁴C in atmospheric CO₂ collected in the lower stratosphere from aircraft during 1965 (strat.for);
• one SAS^® data retrieval routine (strat.sas) to read and print strat.dat; and
• one ASCII data file containing estimates of δ¹⁴C, δ¹³C, and Δ¹⁴C in atmospheric CO₂ collected in the lower stratosphere from aircraft during 1965 (strat.dat)

DATA FILE FORMATS (*.ASC)

This NDP contains 15 data files that provide 1619 estimates of δ¹⁴C, δ¹³C, and Δ¹⁴C in atmospheric CO₂ from 14 locations. The period of record differs by station. The earliest measurements were made in 1962, and the latest estimates are from 1993. Most stations have records only for the 1960s. All of the data files have the same format and none contain missing values. Some δ¹³C values are flagged as mean values; users are urged to pay attention to these flags before analyzing or interpreting the corresponding values.

Each file is sorted by sample collection date and may be read with the following FORTRAN 77 code:

	character labref*9, samdat*13, flag13*1
	real delC14, delC13, corC14
	open(unit=5,file='F.asc')
	open(unit=6)
	read(5,10)
10	format(///////////////)
13	continue
	read (5,15, end=99) labref,week,samdat,delC14,delC13,flag13, 1 corC14,sigma
15	format(A9,1X,I4,2X,A13,4X,F6.1,2X,F5.1,A1,2X,F6.1,4X,I2)

The following SAS^® input statement may also be used to read these files:

input labref $ 1-9 week 11-15 samdat $ 17-30 @34 delC14 7.1 @42 delC13 5.1

flag13 $ 47 corC14 50-55 sigma 60-61;

Stated in tabular form, the contents include the following:

where

LABREF	is a seven-to-eight character site code and sample reference number (e.g., D_00034). The 5-digit sample reference number follows the site code and is separated from the site code byan underscore (i.e., "_") character. All laboratory reference numbers are unique. The site codes and the sampling stations they represent are as follows:   V Kapp Linné, Spitsbergen, Norway   F Fruholmen, Nordkapp, Norway   K Gråkallen, Trondheim, Norway   KV Vassfjellet, Trondheim, Norway   L Lindesnes, Norway   S Santiago de Compostela, Spain   IZ Izaña, Tenerife, Canary Islands   M Mas Palomas, Grand Canary Island   R Rehovot, Israel   D Popenguine, Dakar, Senegal   DF Université Dakar-Fann, Dakar, Senegal   TC N'Djamena, Chad   E Debre Zeit, Addis Ababa, Ethiopia   G Fianarantsoa, Madagascar
WEEK	is the week the NaOH tray was exposed relative to the first week of 1963. Values range from -34 to 1591. Zero refers to the week of December 29, 1962 to January 7, 1963. Negative values denote the number of weeks before 1963 (e.g., -34 refers to the week from April 30, 1962, to May 3, 1962).
SAMDAT	is a thirteen-character field that represents the days, months, and years of the sampling period, typically 4-7 day periods. The beginning date (yy/mm/dd) and ending date (yy/mm/dd) are separated by a hyphen. The earliest sampling date is 620430-620503 (from Gråkallen) and the latest sampling period is 930621-930624 (from Fruholmen).
DELC14	is the uncorrected (for decay) measurement of excess 14C in atmospheric CO2 expressed as δ14C in per mil (º/ºº) relative to the US National Institute of Standards and Technology (NIST, formerly the National Bureau of Standards) oxalic acid standard; 95% of the 14C concentration in this standard represents the normal activity in recent wood for the year 1950 A.D. Values for DELC14 range from 108.5 to 1036.0.
DELC13	represents the deviation in the 13C/12C ratio expressed in per mil (º/ºº) relative to the Pee Dee Belemnite or (Pee Dee River, South Carolina) or PDB standard (Craig 1961). The 13C/12C ratio was measured by mass spectrometry. The δ13C values provided are given as a guide for the calculation of the Δ14C values. When fractionation was not measured, a mean value, normally based on 20-40 samples was used and is denoted by an asterisk (see description of "FLAG13"). Values for DELC13 range from -31.7 to -11.3.
FLAG13	is a one-character flag code used to denote whether the DEL13C estimate was measured (blank) or represents a mean value (asterisk).
CORC14	is the atmospheric 14C content expressed as Δ14C in per mil (not as a percentage). δ14C is corrected for isotopic fractionation through δ13C (DELC13), and for radioactive decay of the 14C reference standard (NIST). Values range from 110.4 to 1040.4.
SIGMA	is the standard deviation for CORC14 expressed as an integer. Values range from 3 to 42.

DATA FILE FORMAT (STRAT.DAT)

This NDP contains one data file that provides eleven estimates of δ¹⁴C, δ¹³C, and Δ¹⁴C in atmospheric CO₂ from the low stratosphere during 1965. High-altitude samples were collected in the Trondheim area using aircraft from the Norwegian Air Force. Flights originated from Örlandet Airport and covered the region bounded by 62-65°N and 6-10°E, at altitudes of 9000-12600 m. Samples were collected using a filter with a 1.4 kg molecular sieve that absorbs CO₂ from the penetrating air. The filter container was placed under the wing of the plane and opened and closed with electrically-operated shutters at both ends. With the plane traveling at a speed of approximately 900 km/hr the filter shutters were opened 15 minutes to allow sufficient amounts of CO₂ to be absorbed.

The file may be read with the following FORTRAN 77 code:

	character sample*6, flag13*1
	real delC13, corC14
	open(unit=5,file='strat.dat')
	open(unit=6)
	read(5,10)
10	format(///////////////)
	write(6,15)
15	format('Sample',3X,'Altitude',3X,'Date of Collection',6X,
	1 'delta',6X,'delta',2X,'Corrected',4X,'Sigma',/,11X,'(m)',
	2 6X,'(Year, Month, Day)',7X,'C14',8X,'C13',3X,'delta C14',
	3 /)
20	continue
	read (5,25, end=99) sample,alt,samdat,delC14,delC13,flag13,
	1 corC14,sigma
25	format(A6,4X,I5,11X,I6,12X,I4,4X,F5.1,A1,4X,I4,8X,I2)

The following SAS^® input statement may also be used to read this file:

input sample $ 1-6 alt 11-15 samdat 27-32 delC14 45-48 @53 delC13 5.1

flag13 $ 58 corC14 63-66 sigma 75-76;

Stated in tabular form, the contents include the following:

where

SAMPLE	is a six character site code and sample reference number (e.g., AS-001). The 3-digit sample reference number follows the site code and is separated from the site code by a hyphen. All laboratory reference numbers are unique. Laboratory reference numbers range from 001 to 013. The site code is always "AS" denoting aircraft sampling.
ALT	is the altitude where the air sample was collected expressed in meters. Values range from 9000 to 12600.
SAMDAT	is a six-digit field that represents the day, month, and year of the sampling date expressed in a yymmdd format. Values range from 650407 to 651014.
DELC14	is the uncorrected (for decay) measurement of excess 14C in atmospheric CO2 expressed as δ14C in per mil (º/ºº) relative to the US National Institute of Standards and Technology (NIST, formerly the National Bureau of Standards) oxalic acid standard; 95% of the 14C concentration in this standard represents the normal activity in recent wood for the year 1950 A.D. Values for DELC14 range from 599 to 1718.
DELC13	represents the deviation in the 13C/12C ratio expressed in per mil (º/ºº) relative to the Pee Dee Belemnite (Pee Dee River, South Carolina) or PDB standard (Craig 1961). The 13C/12C ratio was measured by mass spectrometry. The δ13C values provided are given as a guide for the calculation of the Δ14C values. When fractionation was not measured, a mean value, based on 4 samples was used and is denoted by an asterisk (see description of "FLAG13"). Values for DELC13 range from -11.4 to -3.3.
FLAG13	is a one-character flag code used to denote whether the DEL13C estimate was measured (blank) or represents a mean value (asterisk). Seven of the eleven DELC13 values are flagged with an asterisk.
CORC14	is the atmospheric 14C content expressed as Δ14C in per mil (not as a percentage). 14C is corrected for isotopic fractionation through δ13C (DELC13), and for radioactive decay of the 14C reference standard (NIST). Values range from 554 to 1626.
SIGMA	is the standard deviation for CORC14 expressed as an integer. Values range from 17 to 47.

---

13. LISTING OF THE FORTRAN 77 DATA RETRIEVAL PROGRAMS

The following is a listing of the FORTRAN 77 data retrieval code (ndp057.for) written by the preparers to read and print any of the files containing the station ¹⁴C data.

C This Fortran 77 program was written by VZ to read and write

C Nydal and Lovseth's C14 measurements

      character labref*9, samdat*13, flag13*1

      real delC14, delC13, corC14

      open(unit=5,file='F.asc')

      open(unit=6)

      read(5,10)

 10   format(///////////////)

 13   continue

      read (5,15, end=99) labref,week,samdat,delC14,delC13,flag13,

     1  corC14,sigma

 15   format(A9,1X,I4,2X,A13,4X,F6.1,2X,F5.1,A1,2X,F6.1,4X,I2)

      write(6,20) labref,week,samdat,delC14,delC13,flag13,

     1  corC14,sigma

 20   format(A9,1X,I4,2X,A13,4X,F6.1,2X,F5.1,A1,2X,F6.1,4X,I2)

      goto 13

 99   continue

      close(unit=5)

      close(unit=6)

      stop

      end

The following is a listing of the FORTRAN 77 data retrieval code (strat.for) written by the preparers to read and print the file containing the stratospheric ¹⁴C data.

C This Fortran 77 program was written by TAB to read and write

C Nydal and Lovseth's aircraft C14 measurements

      character sample*6, flag13*1

      real delC13, corC14

      open(unit=5,file='strat.dat')

      open(unit=6)

      read(5,10)

 10   format(///////////////)

      write(6,15)

 15   format('Sample',3X,'Altitude',3X,'Date of Collection',6X,

     1 'delta',6X,'delta',2X,'Corrected',4X,'Sigma',/,11X,'(m)',

     2 6X,'(Year, Month, Day)',7X,'C14',8X,'C13',3X,'delta C14',

     3 /)

 20   continue

      read (5,25, end=99) sample,alt,samdat,delC14,delC13,flag13,

     1  corC14,sigma

 25   format(A6,4X,I5,11X,I6,12X,I4,4X,F5.1,A1,4X,I4,8X,I2)

      write(6,30) sample,alt,samdat,delC14,delC13,flag13,

     1  corC14,sigma

 30   format(A6,4X,I5,11X,I6,12X,I4,6X,F5.1,A1,4X,I4,8X,I2)

      goto 20

 99   continue

      close(unit=5)

      close(unit=6)

      stop

      end

---

14. LISTING OF THE SAS^® DATA RETRIEVAL PROGRAMS

The following is a listing of the SAS^® data retrieval code (ndp057.sas) written by the preparers to read and print any of the files containing the station ¹⁴C data.

***********************************************

* THIS SAS PROGRAM READS AND PRINTS THE NYDAL *

* AND LOVSETH ASCII FILES CONTAINING          *

* GROUND-LEVEL C14 MEASUREMENTS               *

***********************************************


;

data nydal;

infile 'nydal.asc' missover firstobs=17;

input labref $ 1-9 week 11-15 samdat $ 17-30 @34 delC14 7.1 @42 delC13 5.1

      flag13 $ 47 corC14 50-55 sigma 60-61;

proc print;

run;

The following is a listing of the SAS^® data retrieval code (strat.sas) written by the preparers to read and print the file containing the stratospheric ¹⁴C data.

***********************************************

* THIS SAS PROGRAM READS AND PRINTS THE FILE  *

* (STRAT.DAT) CONTAINING C14 MEASUREMENTS     *

* DERIVED FROM AIR SAMPLES COLLECTED ON       *

* NORWEGIAN AIR FORCE AIRCRAFT DURING 1965    *

***********************************************


;

data strat;

infile 'strat.dat' missover firstobs=17;

input sample $ 1-6 alt 11-15 samdat 27-32 delC14 45-48 @53 delC13 5.1

      flag13 $ 58 corC14 63-66 sigma 75-76;

proc print;

run;

---

15. PARTIAL LISTING OF DATA FILES

The following presents a partial listing of one (nydal.asc) of the 15 data files that contain the station ¹⁴C data. This file is identical in format to all data files containing the station ¹⁴C data.

The first 25 lines of the file nydal.asc are as follows:

***********************************************************

* Carbon-14 Measurements in Atmospheric CO2 from Northern *

* and Southern Hemisphere Sites, 1962-1993                *

*                                                         *

* Authors: Reidar Nydal and Knut Lovseth                  *

*          Radiological Dating Laboratory                 *

*          The Norwegian Institute of Technology          *

*          N-7034 Trondheim NTH                           *

*          NORWAY                                         *

*                                                         *

* NDP057 (November 1996)                                  *

***********************************************************




Lab Ref.   Week Sampling Interval delta   delta   corr    sigma

                                  C14     C13     C14




D-00001     10  630304-630311     477.0  -26.5    479.4    12

D-00002     11  630311-630318     494.0  -23.1    486.4     7

D-00004     13  630325-630401     562.0  -24.2    557.4    11

D-00006     15  630408-630415     583.0  -24.2    557.4    11

D-00008     17  630422-630429     580.0  -25.0    578.4    11

D-00010     19  630506-630513     653.0  -23.7*   647.4     9

D-00012     21  630520-630527     661.0  -24.6    658.4    10

D-00014     23  630603-630610     704.0  -24.3    700.4    12

D-00016     25  630617-630624     703.0  -25.0    701.4     8

The last 25 lines of the file nydal.asc are as follows:

TC-00109   576  740107-740114     435.0  -23.7    428.1    10

TC-00110   580  740204-740211     430.0  -22.0    418.1     9

TC-00111   584  740304-740311     427.0  -22.4    416.1     9

TC-00112   588  740401-740408     425.0  -22.4    414.1    10

TC-00113   595  740524-740601     410.0  -23.2    402.1    10

TC-00114   636  750303-750310     403.0  -21.8    391.0    10

TC-00115   680  760105-760112     396.0  -21.6    382.9    11

TC-00116   684  760202-760209     400.0  -21.0    384.9     6

TC-00117   688  760301-760308     392.0  -18.6    370.9     8

TC-00118   692  760329-760405     369.0  -20.2    352.9    11

TC-00119   696  760426-760503     357.0  -24.2    350.9     9

TC-00120   700  760524-760531     410.0  -22.7    399.9    10

V-00001     25  630619-630626     760.0  -27.8    768.4    13

V-00003     27  630701-630708     801.0  -25.8    802.4    12

V-00005     29  630715-630722     941.0  -27.5    949.4    11

V-00007     31  630729-630805     948.0  -25.2    947.4    10

V-00009     33  630812-630819     998.0  -26.2   1001.4    11

V-00011     35  630827-630903    1006.0  -26.9   1012.4    13

V-00013     37  630909-630916     994.0  -26.4*   997.4    12

V-00015     39  630923-631001     960.0  -28.1    970.4    10

V-00017     41  631007-631015     964.0  -26.4*   969.4    11

V-00019     43  631022-631029     949.0  -22.8    938.4    11

V-00055     79  640629-640706     878.0  -26.8    883.3    11

V-00057     81  640713-640720     973.0  -26.4*   976.3    11

V-00059     83  640727-640803     919.0  -26.4*   922.3    11

The following is a complete listing of the data file (strat.dat) containing the stratospheric ¹⁴C data.

***********************************************************

* Carbon-14 Measurements in Atmospheric CO2 from Northern *

* and Southern Hemisphere Sites, 1962-1993                *

*                                                         *

* Authors: Reidar Nydal and Knut Lovseth                  *

*          Radiological Dating Laboratory                 *

*          The Norwegian Institute of Technology          *

*          N-7034 Trondheim NTH                           *

*          NORWAY                                         *

*                                                         *

* NDP057 (November 1996)                                  *

***********************************************************




Sample   Altitude   Date of Collection     delta     delta  Corrected   Sigma

           (m)      (Year, Month, Day)      C14       C13   delta C14




AS-001    12600           650407            1459     -8.5*    1376        28

AS-003    12000           650513            1660     -8.5*    1577        47

AS-004    11900           650601            1140     -8.5*    1067        18

AS-005    12000           650614            1718     -8.5*    1626        47

AS-006    12000           650623            1669     -8.1     1576        32

AS-008    12000           650721            1437     -8.5*    1355        35

AS-009    12000           650804            1116    -11.2     1055        33

AS-010     9000           650821             814     -3.3      734        17

AS-011    12000           650907             854     -8.5*     737        23

AS-012    12000           650924             986     -8.5*     919        26

AS-013    12000           651014             599    -11.4      554        33

---

16. VERIFICATION OF DATA TRANSPORT

The data files contained in this NDP may be read with the FORTRAN 77 or SAS^® data retrieval programs provided. To verify that the data have been correctly transported to their systems, users should generate some or all of the statistics presented in Tables 2 and 3. These tables present simple summary statistics for the file that contains data from all 14 sites (i.e., file nydal.asc) and the file that contains the stratospheric ¹⁴C measurements (i.e., file strat.dat). If the statistics generated by the user differ from those presented here, the data files may have been corrupted in transport.

These statistics are presented only as a tool to ensure proper reading of the data files. They are not to be construed as summaries of the data sets.

Table 2. Characteristics of numeric variables in the file containing carbon isotope data
from all 14 sampling locations

Table 3. Characteristics of numeric variables in the file containing stratospheric carbon isotope
data derived from air samples collected by aircraft during 1965

---

APPENDIX A

FIGURES SHOWING TROPOSPHERIC AND
STRATOSPHERIC ¹⁴C MEASUREMENTS IN
ATMOSPHERIC CO₂ FROM 14 NORTHERN
AND SOUTHERN HEMISPHERE SITES

Fig. A-1. Corrected ¹⁴C measurements from air samples collected at Kapp Linné, Fruholmen, Gråkallen, and Vassfjellet

Fig. A-2. Corrected ¹⁴C measurements from air samples collected at Lindesnes, Norway;

Santiago de Compostela, Spain;and Rehovot, Israel

Fig. A-3. Corrected ¹⁴C measurements from air samples collected at Izaña, Canary Islands; Mas Palomas,

Grand CanaryIsland; Dakar, Senegal; Dakar-Fann, Senegal; and N'Djamena, Chad

Fig. A-4. Corrected ¹⁴C measurements from air samples collected at Debre Zeit, Ethiopia; Fianarantsoa,
Madagascar; and by aircraft flying in the low stratosphere above Trondheim, Norway

---

APPENDIX B

REPRINTS OF PERTINENT LITERATURE

Tracing Bomb ¹⁴C in the Atmosphere 1962-1980, by R. Nydal and K. Lövseth, 1983. Journal of Geophysical Research 88:3621-42.

The copyright permission kindly extended to the Carbon Dioxide Information Analysis Center by the American Geophysical Union did not include reprinting in the electronic form, only printed matter.