W. J. Jenkins et al.: A comprehensive global oceanic dataset of helium isotope and tritium measurements 
Table 2. Quality flag meaning. 
Quality flag Meaning 
number 
Normal data, no problems reported 
Questionable data: may not fit profile 
or some other doubt 
Average of two or more measurements 
Missing (null) data 
9 
3 
In the spirit of the WOCE, CLIVAR, and GO-SHIP? con- 
vention, the combination of ExpoCode, Station, CastNo, and 
Bottle should uniquely define a sample. That is, no two data 
records should have the same combination of these values. 
This has been followed with most of the information here: 
when a sample’s station, cast, or bottle number were not pro- 
vided (in the case of literature data), arbitrary but unique 
aumbers were assigned. In order to supplement this identi- 
fication, we added a unique integer record ID number. 
2.5 Data formats and availability 
The dataset’s DOI is https://doi.org/10.25921/c1sn-9631 
(Jenkins et al., 2018b). The data are available for down- 
load from the U.S. National Oceanic and Atmospheric 
Administration’s National Centers for Environmental In- 
formation website at https://www.nodc.noaa.g0ov/ocads/data/ 
0176626.xml or alternately http://odv.awi.de/data/ocean/ 
jenkins-tritium-helium-data-compilation/ in a number of for- 
mats. For maximum flexibility, we suggest one of the follow- 
ing three database formats: Microsoft Access®, PostgreSQL, 
or ODV (Ocean Data View). In addition, the three tables are 
available as four files (the main data table is split into two 
to avoid spreadsheet row-number limitations) in Microsoft 
Excel® or as comma-separated plain text files. The data are 
also available in NetCDF format. Finally, the data table is 
available for download as a MATLAB® binary data file. 
3 Scope and nature of the dataset 
We provide some graphics to indicate the scope and nature 
of the data holdings. These include time histories of analyses 
per year for both types of measurements (Fig. 2) and maps of 
sampling locations (Fig. 3). The intent is to provide a broad 
overview of the character of the datasets while not overinter- 
preting its details and features. 
?7WOCE is the World Ocean Circulation Experiment (e.g., see 
https://www.nodc.noaa.gov/woce/, last access: 1 April 2019), CLI- 
VAR is the Climate and Ocean — Variability, Predictability, and 
Change (e.g., see http://www.clivar.org/about, last access: 1 April 
2019), and GO-SHIP is the Global Ocean Ship-Based Hydrographic 
Investigations Program (see http://www.go-ship.org/, last access: 
1 April 2019). 
Wwww.earth-syst-sci-data.net/11/441/20 19 
SE Ta U 
5 4000 ® 
3 2000 
: 0 
1950 1960 1970 1980 1990 2000 2010 
8000 © 
DD 
E 6000 ) 
ka) 
z 4000 
3 
= 2000 
0 ak la 
1950 1960 1970 1980 1990 2000 2010 
Figure 2. Time distributions of annual tritium (a) and helium (b) 
measurements. 
The temporal distribution of oceanic tritium measurements 
begins in the early 1950s with the development of enrichment 
and counting capabilities suitable for environmental levels, 
the recognition of the existence of cosmogenic tritium pro- 
duction (Cornog and Libby, 1941; Currie et al., 1956; Grosse 
et al., 1951; Kaufman and Libby, 1954; Libby, 1946), and 
the desire to measure its distribution in the hydrologic cycle. 
The advent of atmospheric thermonuclear tests in the 1950s 
and early 1960s dwarfed the natural global inventory (Weiss 
and Roether, 1980), which motivated an increase in oceanic 
measurements in the 1960s. The initiation of global ocean 
chemistry, hydrographic, and tracer survey efforts (especially 
GEOSECS?) further increased this activity. A final boost to 
tritium measurement rates occurred with the development of 
the *He regrowth method (Clarke et al., 1976) coupled with 
even more ambitious global surveys (such as WOCE, CLI- 
VAR, and GO-SHIP). 
The helium sampling time history was basically initiated 
and motivated by the discovery of primordial °He injection 
into the deep waters (Clarke et al., 1969), which drove the 
inclusion of helium isotope measurements in the GEOSECS 
program. It was quickly realized that the existence of tfritiu- 
genic He (that produced by the in situ decay of tritium) of- 
fered the potential for a dating tool as well (Jenkins et al., 
1972; Jenkins and Clarke, 1976), which spurred on continued 
helium isotope measurements in the global surveys. These 
were enabled by a number of laboratories coming “online” 
in the 1970s and 1980s. 
The tritium and helium sampling locations shown in Fig. 3 
are dominated by the global survey programs’ cruise tracks, 
but also include a number of ocean island monitoring sites 
(especially for tritium). One difference in the two maps is the 
extra tritium sampling in the Arctic, perhaps largely driven 
by H. Göte Östlund’s motivation to exploit this isotope’s po- 
tential in studying the Arctic fresh water system (Östlund. 
1982). 
3GEOSECS is the Geochemical Ocean Sections Survey 
Earth Syst. Sci. Data. 11, 441-454. 2019