NDP-057 (1996)

Download the Data and ASCII Documentation files of NDP-057

Download View, download, or print PDF documentation of NDP-057

CARBON-14 MEASUREMENTS IN ATMOSPHERIC CO2
FROM NORTHERN AND SOUTHERN
HEMISPHERE SITES, 1962-1993



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 37831-6335
managed by
LOCKHEED MARTIN ENERGY RESEARCH CORP.
for the
U.S. DEPARTMENT OF ENERGY
under contract DE-AC05-96OR22464


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.


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


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


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.

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 14C 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 (14C) 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 14C, 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 (14C) relative to the NIST standard, fractionation 13C (13C) relative to the Pee Dee Belemnite (PDB) standard, and corrected 14C (14C) excess; and the standard deviation for 14C. The 14C 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 14C 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 14C level during the early 1960s mainly as a result of springtime transport of bomb 14C 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.


PART 1: OVERVIEW


1. NAME OF THE NUMERIC DATA PACKAGE

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


2. PRINCIPAL INVESTIGATORS

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


3. KEYWORDS

Radiocarbon, 14C, atmospheric CO2, quantitative NaOH absorption, carbon isotopes, bomb 14C, 14C, 14C, 13C, troposphere, stratosphere, aircraft sampling


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 14C 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 14C 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).


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 14C 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 14C, 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). 14C is expressed in per mil (not as a percentage) and calculated using the following two steps:

14 = 14C - 2(13C + 25)(1 + 14C/1000) (1)
14C = 14 + 1000(e (1950-t) - 1)(2)





In step 1, the 14C excess (14) is only corrected for isotopic mass fractionation. 14C represents the uncorrected (for decay) 14C relative to the NIST standard and 13C 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 13C 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 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 14C 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).


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 14CO2 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 14C 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 14C 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 14C 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.


7. DATA LIMITATIONS AND RESTRICTIONS

Please note that the 13C 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 13C and identified by a flag code. These mean values were calculated from 20-40 ground-level measurements or 4 high-altitude measurements.


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.


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 14C, 13C, and corrected 14C data at each site were calculated and assessed for reasonableness.

4. All 14C, 13C, and corrected 14C 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.


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 37831-6335, 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!


PART 2: CONTENT AND FORMAT OF DATA FILES


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.

File number, description,
and name (in parentheses)
Logical
records
FTP file
size(kB)
Record
formata
Block
size
Record
length
1. General descriptive information file (ndp057.doc)255 13.3 FB 8000 100
2. FORTRAN 77 data retrieval code to read and print the files containing the atmospheric carbon isotope records (files 4-18) (ndp057.for) 21 0.7 FB 8000 80
3. SAS® data retrieval code to read and print files 4-18 (ndp057.sas) 12 0.4 FB 8000 80
Data files containing 14C, 13C, and 14C estimates in
atmospheric CO2 from the following
Northern and Southern Hemisphere sites
4. Kapp Linné, Spitsbergen, Norway (V.asc) 59 1.6 FB 6100 61
5. Fruholmen, Nordkapp, Norway (F.asc) 531 32.5 FB 6100 61
6. Gråkallen, Trondheim, Norway (K.asc) 44 2.6 FB 6100 61
7. Vassfjellet, Trondheim, Norway (KV.asc) 32 1.8 FB 6100 61
8. Lindesnes, Norway (L.asc) 64 3.8 FB 6100 61
9. Santiago de Compostela, Spain (S.asc) 104 6.3 FB 6100 61
10. Izaña, Tenerife, Canary Islands (IZ.asc) 308 19.3 FB 6100 61
11. Mas Palomas, Grand Canary Island (M.asc) 183 11.4 FB 6100 61
12. Rehovot, Israel (R.asc) 28 1.6 FB 6100 61
13. Popenguine, Dakar, Senegal (D.asc) 48 2.8 FB 6100 61
14. Dakar-Fann, Senegal (DF.asc) 84 5.1 FB 6100 61
15. N'Djamena, Chad (TC.asc) 119 7.2 FB 6100 61
16. Debre Zeit, Ethiopia (E.asc) 84 5.2 FB 6100 61
17. Fianarantsoa, Madagascar (G.asc) 185 11.4 FB 6100 61
18. Single data file containing the 14C, 13C, and 14C estimates
in atmospheric CO2 from all 14 sites (nydal.asc)
1635 101.8 FB 6100 61
19. FORTRAN 77 data retrieval code to read and print the file
containing the stratospheric 14C, 13C, and 14C estimates
in atmospheric CO2 derived from air samples collected by
aircraft during 1965 from the Trondheim area
(62-65°N, 6-10°E) (strat.for)
26 0.9 FB 8000 80
20. SAS® data retrieval code to read and print file 21 (strat.sas) 13 0.5 FB 8000 80
21. Stratospheric 14C, 13C, and 14C estimates in atmospheric
CO2 derived from air samples collected by aircraft
during 1965 from the Trondheim area (62-65°N, 6-10°E) (strat.dat)
27 1.9 FB 7600 76
TOTAL 3862 232.1

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


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:

DATA FILE FORMATS (*.ASC)

This NDP contains 15 data files that provide 1619 estimates of 14C, 13C, and 14C 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 13C 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:

Variable Variable
type
Variable
format
Starting
column
Ending
column
LABREF Alphanumeric 9 1 9
WEEK Numeric 5 11 15
SAMDAT Alphanumeric 14 17 30
DELC14 Numeric 7.1 34 40
DELC13 Numeric 5.1 42 46
FLAG13 Character 1 47 47
CORC14 Numeric 6.1 50 55
SIGMA Numeric 2 60 61

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:

VKapp 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 14C 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 13C values provided are given as a guide for the calculation of the 14C 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 14C in per mil (not as a percentage). 14C is corrected for isotopic fractionation through 13C (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 14C, 13C, and 14C 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:

Variable Variable
type
Variable
format
Starting
column
Ending
column
SAMPLE Alphanumeric 6 1 6
ALT Numeric 5 11 15
SAMDAT Numeric 6 27 32
DELC14 Numeric 4 45 48
DELC13 Numeric 5.1 53 57
LAG13 Character 1 58 58
CORC14 Numeric 4 63 66
SIGMA Numeric 2 75 76

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 14C 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 13C values provided are given as a guide for the calculation of the 14C 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 14C in per mil (not as a percentage). 14C is corrected for isotopic fractionation through 13C (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

VariableNumber of
observations
MeanStandard
deviation
Minimum
value
Maximum
value
WEEK 1619 534.8097591 490.3078555 -34 1591
DELC14 1619 502.1426189 237.0226744 108.5 1036.0
DELC13 1619 -24.2290303 2.3573591 -31.7 -11.3
CORC14 1619 496.9402718 236.6761277 110.4 1040.4
SIGMA 1619 9.1432983 3.1888204 3 42

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

VariableNumber of
observations
MeanStandard
deviation
Minimum
value
Maximum
value
ALT 11 11772.73 938.1800564 9000 12600

SAMDAT

11 650722.64 188.6336517 650407 651014

DELC14

11 1222.91 387.7791780 599 1718

DELC13

11 -8.50 2.0712315 -11.4 -3.3

CORC14

11 1143.27 380.9330889 554 1626

SIGMA

11 30.82 9.9981817 17 47


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.