Tritium and helium isotope data provide key information on ocean
circulation, ventilation, and mixing, as well as the rates of biogeochemical
processes and deep-ocean hydrothermal processes. We present here global
oceanic datasets of tritium and helium isotope measurements made by numerous
researchers and laboratories over a period exceeding 60 years. The dataset's
DOI is 10.25921/c1sn-9631, and the data are available at
https://www.nodc.noaa.gov/ocads/data/0176626.xml (last access: 15 March
2019) or alternately
http://odv.awi.de/data/ocean/jenkins-tritium-helium-data-compilation/
(last access: 13 March 2019) and includes approximately 60 000 valid tritium
measurements, 63 000 valid helium isotope determinations, 57 000 dissolved
helium concentrations, and 34 000 dissolved neon concentrations. Some
quality control has been applied in that questionable data have been flagged
and clearly compromised data excluded entirely. Appropriate metadata have
been included, including geographic location, date, and sample depth. When
available, we include water temperature, salinity, and dissolved oxygen. Data
quality flags and data originator information (including methodology) are
also included. This paper provides an introduction to the dataset along with
some discussion of its broader qualities and graphics.
Introduction
The global oceanic distributions of tritium (3H, a radioactive
isotope of hydrogen with a half-life of 12.3 years), its daughter product
3He, and helium isotopes in general arise from the complicated
interplay of ocean ventilation, circulation, and mixing, with the hydrologic
cycle, air–sea exchange, and geological volatile input. Observations of the
delivery of tritium to the ocean and its redistribution are a useful tool for
diagnosing gyre- and basin-scale ventilation and circulation (Doney et al.,
1992; Doney and Jenkins, 1994; Dorsey and Peterson, 1976; Dreisigacker and
Roether, 1978; Fine and Östlund, 1977; Fine et al., 1987, 1981; Jenkins
et al., 1983; Jenkins and Rhines, 1980; Michel and Suess, 1975; Miyake et
al., 1975; Östlund, 1982; Sarmiento, 1983; Weiss and Roether, 1980; Weiss
et al., 1979).
In shallow waters, away from seafloor hydrothermal vents, the combination of
tritium and 3He may be used to determine the time elapsed since a
water parcel was at the sea surface, making it a useful tool for diagnosing
ventilation and circulation on seasonal through decade timescales (Jenkins,
1987, 1998, 1977). The ingrowth and evasion of tritiugenic 3He from
the thermocline is also useful as a flux gauge for constraining the rate of
nutrient return to the ocean surface (Jenkins, 1988; Jenkins and Doney, 2003;
Stanley et al., 2015) as well as upwelling in coastal regions (Rhein et al.,
2010). Finally, the distribution of helium isotopes in the deep sea provides
important quantitative constraints on the impact of submarine hydrothermal
venting on many elements because the global hydrothermal helium flux is well
known (Bianchi et al., 2010; Holzer et al., 2017; Schlitzer, 2016). This
makes 3He useful as a flux gauge (German et al., 2016; Jenkins et
al., 1978, 2018a; Lupton and Jenkins, 2017; Resing et al., 2015; Roshan et
al., 2016). Consequently, there have been numerous measurements of these
properties over the years, particularly under the aegis of major
observational programs like GEOSECS (Bainbridge et al., 1987), TTO (Jenkins
and Smethie, 1996), WOCE
(http://www.nodc.noaa.gov/woce/wdiu/diu_summaries/whp/index.htm, last
access: 1 April 2019), CLIVAR (http://www.clivar.org, last access:
1 April 2019), GO-SHIP (http://www.go-ship.org, last access: 1 April
2019), and GEOTRACES (http://www.geotraces.org, last access: 1 April
2019). It seems valuable to assemble all existing data, including those
measured prior to and outside of these programs, along with appropriate
metadata, in one place to facilitate further use and analysis. This is a
report of these efforts.
MethodsTritium measurement methodology
There are at present three distinct methods for the determination of tritium
in water samples: direct measurement of tritium abundance by accelerator mass
spectrometry (AMS), radioactive counting of tritium decay rate, and the
daughter product (3He) ingrowth method. The first method (AMS) has
not been used for the measurement of environmental tritium levels but is
better suited to measuring high tritium concentrations in small samples,
largely for biomedical tracer research (Brown et al., 2005; Chiarappa-Zucca
et al., 2002; Glagola et al., 1984; Roberts et al., 2000). The second method
usually involves isotopic enrichment of hydrogen from the water samples,
either by electrolysis (e.g., Östlund and Werner, 1962) or thermal
diffusion (Israel, 1962) followed by low-level radioactive counting, either
by liquid scintillation (Momoshima et al., 1983) or gas proportional counting
(Bainbridge et al., 1961). Measurements are made relative to prepared
standards (Unterweger et al., 1980), and accuracy appears to be limited by
the reproducibility of the enrichment process to 3 %–10 % (Cameron,
1967).
The third method, 3He ingrowth, is a three-step method. First, it
involves degassing of a quantity (∼1 to 1000 mL) of water to
remove all dissolved helium. Second, the degassed water is stored in a
helium leak-tight container (usually low-He-permeability aluminosilicate
glass or metal) for a period of several weeks to a year or more. Experience
indicates that it is necessary to shelter the stored samples from cosmic
rays since there is a latitude-dependent cosmogenic 3He production rate
that masquerades as “tritium signal” (Lott and Jenkins, 1998).
Finally, the ingrown 3He is extracted from the water sample and mass
spectrometrically analyzed (Clarke et al., 1976; Ludin et
al., 1997). The last method, although it involves a potentially lengthy
incubation period, is chemically simpler and does not involve isotopic
enrichment steps. As such, it offers intrinsically greater accuracy (limited
by standardization of the mass spectrometer, typically better than 1 %)
and a lower ultimate detection limit (Jenkins et al., 1983;
Lott and Jenkins, 1998).
Helium isotope measurement methodology
Water samples are usually drawn from Niskin bottles into a helium leak-tight
container either for shipboard (Lott and Jenkins, 1998;
Roether et al., 2013) or shore-based gas extraction. The latter involves
either clamped (Weiss, 1968) or crimped copper tubing (Young and
Lupton, 1983). The extracted gases are subsequently purified and
concentrated, usually cryogenically (Lott, 2001; Lott and Jenkins, 1984;
Ludin et al., 1997), and expanded into a mass spectrometer for isotopic
analysis. While time-of-flight mass spectrometry has been used
(Mamyrin, 2001; Mamyrin et al., 1970), most oceanic helium
isotope measurements have been made using multi-collector magnetic sector
instruments (whereby ions are electrostatically accelerated and deflected
by a magnetic field, e.g., Bayer et al., 1989; Clarke et al., 1969; Lott and
Jenkins, 1998, 1984; Ludin et al., 1997). Measurements are typically
standardized to marine air and corrected for any sample-size-dependent ratio
effects determined by measurement of different-sized air aliquots. Depending
on the amount of tritium in the water and the length of time a water sample
is stored prior to gas extraction, it is generally necessary to correct the
3He/4He results for decay of tritium during storage. For very deep
and old samples, e.g., at 3000 m in the North Pacific, where tritium
concentrations are very low, this correction may be inconsequential.
Helium and neon concentration measurements
To make full use of the helium isotopic ratio measurements, one needs to know
at least the concentration of helium in the samples as well. This allows
investigators to calculate the actual concentration of both 3He and
4He in samples and, with some assumptions, to estimate the amount
of non-atmospheric 3He – whether it be from tritium decay or
hydrothermal input – and 4He. The estimate can be further improved
with knowledge of neon concentrations. Since neon is similar to helium in
terms of its solubility in seawater and there are no known significant
non-atmospheric sources of neon in the ocean, its concentration is a direct
tracer of processes like air bubble injection at the sea surface. As an
example, we show in Fig. 1 the relationship between the helium and neon
saturation anomalies
The saturation anomaly of a gas is the percent
deviation of the measured concentration relative to the expected
concentration of the sample in equilibrium with air at one atmosphere, for
example, as defined by ΔHe=100(C/C∗-1), where
C∗ is the solubility equilibrium concentration at the temperature and
salinity of the sample.
for approximately 2000 near-surface samples. The
saturation anomalies range from significantly below zero to as much as
10 %–15 %. The negative values may arise from lower barometric
pressures or air–sea disequilibrium during cooling. However, there may be systematic offsets due to laboratory
standardization as well. The higher values may also reflect such biases but
also may be due to air bubble entrapment during sampling at sea. The solid
line in Fig. 1 represents a type-II linear regression of the data and has a
slope of near unity, which is expected given the similarity of the two gases.
However, the slope is greater than the precise ratio expected (0.8 to 0.9
depending on temperature) based on their solubilities and atmospheric
abundances, possibly due to differing air–sea exchange rates. Consideration
must be given to these and other factors when using this data (e.g., Fuchs et
al., 1987; Roether et al., 1998).
A scatter plot of helium and neon saturation anomalies for nearly
2000 near-surface (<20 m depth) samples from the dataset. The solid line
is a type-II linear regression of the data.
Helium and neon concentration measurements are typically made by mass
spectrometric peak height manometry, that is, by comparison of major isotope
ion currents (4He+ and 20Ne+) between the unknown to
helium and neon derived from an aliquot of marine air. The air aliquot size
is determined from a knowledge of the barometric pressure, relative
humidity, and temperature at which the previously evacuated air standard
reservoir was filled and the volume of the aliquot. Generally the ion
current is assumed to be a linear function of the sample size (number of
atoms) over some narrow range but also can be corrected by construction of
a standard curve using different sized aliquots. Some measurements (notably
the GEOSECS expedition) were made by splitting the gas extracted from the
water sample and measuring the helium and neon contents separately using
isotope dilution (with 3He and 22Ne spikes).
Data organization
We have compiled a comprehensive dataset consisting of helium isotope and
tritium measurements in oceanic waters made by numerous laboratories over
the past 6 decades. The dataset includes ∼60000 tritium and
∼63000 helium isotope measurements, ∼57000
dissolved helium concentrations, and ∼34000 dissolved neon
concentrations in ocean water taken from 1952 to 2015 (for tritium) and from
1967 to 2015 for helium. In addition to “spot sampling”, there are
∼380 cruises, with sampling from >5400 locations
for tritium and ∼5600 locations for helium. The helium data
are from 8 different laboratories and the tritium data from 15 laboratories
worldwide. In addition to including measurement uncertainties, a data
quality flag, and data source, each data point is accompanied by location
(latitude, longitude, depth) and time (decimal year) of sampling. When
available, water temperature, salinity, and dissolved oxygen measurements
are included.
A number of the earliest measurements were obtained from publications. In
those cases, the publication source is given. If the data were transcribed
from tables, the table number and page is also given. In the event that the
data were only available graphically, a computer program to digitize the
data from plots was used, and in the rare cases in which graph quality was
sufficiently poor to degrade the precision of the data, the uncertainties
were commensurately increased to reflect it. Where data had been assigned a
Digital Object Identifier (DOI), this is also included.
Fields (columns) in the main data table.
Field nameField typeField descriptionExpoCodeShort textUnique string identifying cruise/expeditionSect_IDShort textString identifying Ocean Section (WOCE, CLIVAR, or GEOTRACES)StationShort textStation name or numberCastNoShort textCast name or number at that stationBottleShort textBottle name or number on that castStaDateNumberDecimal year of samplingLatitudeNumberNorth latitude in decimal degrees (from -90 to +90)LongitudeNumberEast longitude in decimal degrees (from -180 to +180)StaDepthNumberBottom depth at station location in metersPressureNumberBottle depth (actually pressure) measured in dbarTemperatureNumberIn situ temperature in degrees centigradeTemperature_FlagIntegerTemperature quality flag (see QF table)SalinityNumberSample salinity in PSUSalinity_FlagIntegerSalinity quality flag (see QF table)OxygenNumberDissolved oxygen in µmol kg-1Oxygen_FlagIntegerDissolved oxygen flag (see QF table)TritiumNumberTritium in TU at time of samplingTritium_ErrorNumberUncertainty in TU at time of samplingTritium_FlagIntegerTritium quality flag (see QF table)Tritium_PIShort textPrinciple investigator or measurer of tritiumTritium_PI_InstShort textInstitution or laboratory where tritium was measuredTritium_MethodShort textShort descriptor of tritium sampling/analysis methodDelHe3NumberHelium isotope ratio anomaly relative to atmosphere in percentDelHe3_ErrorNumberUncertainty in helium isotope ratio anomalyDelHe3_FlagIntegerHelium isotope ratio anomaly quality flag (see QF table)HeliumNumberDissolved helium concentration in nmol kg-1Helium_ErrorNumberUncertainty in dissolved helium concentration in nmol kg-1Helium_FlagIntegerDissolved helium quality flag (see QF table)NeonNumberDissolved neon concentration in nmol kg-1Neon_ErrorNumberUncertainty in dissolved neon concentration in nmol kg-1Neon_FlagIntegerDissolved neon quality flag (see QF table)Helium_PIShort textPrinciple investigator or measurer of helium (and neon)Heliulm_PI_InsShort textInstitution or laboratory where tritium was measuredHelium_MethodShort textShort descriptor of helium sampling/analysis methodReference_CodeShort textData origin or link to paper discussing dataReference_SourceShort textData source within reference (e.g., table, figure) if relevantDOIShort textDigital Object Identifer of original dataset (if existing)CommentShort textAdditional information or commentsRecord_IDLong integerUnique record identifier number
The dataset (provided in several digital formats described below) consists
of three tables. The REFERENCES table is a list of the data sources keyed by
the text variable “Reference_Code” found in the main data
table. This provides attribution or more information regarding the data
origin. The METHODS table provides a more complete description of the fields
“Tritium_Method” and “Helium_Method” in
the main data table. This is intended to provide useful interpretive
information regarding how the sampling and/or measurements were
accomplished. The main data table fields are described in Table 1. Most data
fields have an associated quality flag field whose meaning is summarized in
Table 2. Following WOCE ocean data convention, normal acceptable data are
associated with a quality flag of 2, whereas questionable data have a flag
of 3. Results obtained by averaging two or more replicates are signified with
a flag of 6. When fields are missing for a given record, the data are entered
as -999 and the corresponding quality flag is 9. The tritium, helium, helium
isotope, and neon data also have an associated uncertainty field (e.g.,
“Tritium_Error”), which is the estimated uncertainty in the
data points. This is either provided by the data measurer or an estimate
based on described procedures and can vary greatly between methods and
laboratories, so the user is advised to be aware of this value.
Quality flag meaning.
Quality flagMeaningnumber2Normal data, no problems reported3Questionable data: may not fit profileor some other doubt6Average of two or more measurements9Missing (null) data
In the spirit of the WOCE, CLIVAR, and GO-SHIP
WOCE is the World
Ocean Circulation Experiment (e.g., see
https://www.nodc.noaa.gov/woce/, last access: 1 April 2019), CLIVAR 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).
convention, 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 provided (in the case of
literature data), arbitrary but unique numbers were assigned. In order to
supplement this identification, we added a unique integer record ID number.
Data formats and availability
The dataset's DOI is 10.25921/c1sn-9631 (Jenkins et al., 2018b). The data
are available for download from the U.S. National Oceanic and Atmospheric
Administration's National Centers for Environmental Information website at https://www.nodc.noaa.gov/ocads/data/0176626.xml or alternately
http://odv.awi.de/data/ocean/jenkins-tritium-helium-data-compilation/ in a
number of formats. For maximum flexibility, we suggest one of the following
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.
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 overinterpreting its details and features.
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 production (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
GEOSECS is the Geochemical Ocean Sections Survey.
)
further increased this activity. A final boost to tritium measurement rates
occurred with the development of the 3He regrowth method
(Clarke et al., 1976) coupled with even more ambitious global
surveys (such as WOCE, CLIVAR, and GO-SHIP).
Time distributions of annual tritium (a) and
helium (b) measurements.
Tritium and helium sample locations.
The helium sampling time history was basically initiated and motivated by the
discovery of primordial 3He 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
tritiugenic3He (that
produced by the in situ decay of tritium) offered 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 potential in
studying the Arctic fresh water system (Östlund, 1982).
Global ocean surface water (depth <50 m) tritium concentrations
(in TU) for selected latitude bands.
It is well known that the delivery of bomb tritium to the ocean was a
reflection of the distribution of the atmospheric tests and occurred in two
principle modes: a dominant pulse-like injection in the Northern Hemisphere
and a much smaller more “diffuse” input into the Southern Hemisphere
(Doney et al., 1992). The former mode was dominated by the early
1960s American and USSR tests that occurred just prior to the 1963 Partial
Test Ban Treaty, while the southern hemispheric tests were carried out
predominantly by the UK and France. Weiss and Roether (1980) estimated the
delivery of approximately 1500 GCi to the Northern Hemisphere and 480 GCi to
the Southern Hemisphere by the end of 1972. The latitudinal trends can be
seen in Fig. 4, which is a plot of near-surface (<50 m depth) water
tritium concentrations vs. time for a number of latitude bands. Most striking
is the northward increase in the concentration (y-axis) ranges. The
time–latitude trends in Fig. 4 reflect this globally asymmetric delivery,
but much of the structure caused by regional variations in atmospheric input
and ocean circulation may be masked due to conflating major ocean basins in
the groupings.
As a transient tracer, tritium offers an opportunity to visualize the
ventilation of deep waters on decade to century timescales. Benchmark
observations of water column tritium concentrations during the GEOSECS
Atlantic Expedition reveal North Atlantic deep water formation in a graphic
manner (Östlund et al., 1974). The evolution of the tritium distributions
is also valuable as they penetrate the subtropical thermocline and also
intermediate and deep waters. Figure 5 shows four snapshots of tritium
distributions on a section along approximately 52∘ W in the North
Atlantic between the South American and North American coasts (see map
inset). Tritium concentrations are decay-corrected to a common midpoint in
time (1997) for comparison. While the last three occupations are conveniently
along the same cruise track (courtesy of WOCE, CLIVAR, and GO-SHIP), the
first is a composite from several cruises of opportunity taken over an
approximately 1-year period at roughly the same longitude. One can readily
see the downward propagation and ultimate dispersion of the bomb tritium
pulse within the main thermocline (the upper 1000 m), and the progressive
ingrowth of tritium in the intermediate layer (1500–2500 m depth) and in
the bottom layers (∼4000 m) is striking. One can also see the
repartitioning of tritium inventories in the upper waters, both due to
vertical exchange and ventilation but also due to the continued accumulation
of this bomb fallout isotope at subtropical latitudes (similar to bomb
radiocarbon, as observed by Broecker et al., 1995) from more tritium-rich
waters to the north.
Four meridional tritium sections along roughly 52∘ W in the
North Atlantic taken in 1982, 1997, 2003, and 2012. The tritium
concentrations have been decay-corrected to a common time (1 January 1997) for
comparison. Contour intervals are 0.2 TU97, and measurement uncertainties
are of order 0.01 TU97 or better. Due to differences in cruise tracks,
the topography for the 1982 occupation differs from the others.
Equally important is evidence of the southward propagation of the transient
tracer along the deep western boundary current system from Nordic and
Labrador seas (Doney and Jenkins, 1994). This first appears in 1982
at the northern end of the section between 3000 and 4000 m depth near the
bottom of the continental slope. As time progresses, it grows in at
intermediate (∼1500 m) and deeper (3500–4000 m) depths at
the southern end. This clearly marks the net advective timescales for the
deep- and intermediate-depth western boundary currents.
Figure 6 shows the corresponding helium isotope anomaly distribution for the
tritium sections. Interpretation of the helium isotope ratio anomaly is a
little more complicated than the invasion of bomb tritium, but the buildup
of tritiugenic 3He within the main thermocline is an important diagnostic of
vertical transport for the subtropical main thermocline. Its retention and
back-flux to the ocean surface is a uniquely valuable transient tracer
observation, one that parallels the buildup and reflux of inorganic
nutrients in the thermocline (e.g., nitrate and phosphate) but in a
quantifiably defined manner. Observations of surface water 3He excesses
(not shown here) have been used as flux gauges to quantify/constrain
regional-scale new production rates (Jenkins, 1988; Jenkins and Doney,
2003; Stanley et al., 2015) as well as upwelling rates (Rhein
et al., 2010).
Four meridional δ3He sections along roughly
52∘ W in the North Atlantic taken in 1982, 1997, 2003, and 2012.
Contour intervals are 1 %, and measurement uncertainties are 0.15 %.
Due to differences in cruise tracks, the topography for the 1982 occupation
differs from the others.
We also include a time series (plotting only the upper 2000 dbar in Fig. 7) for stations within 200 km of Bermuda (32.3∘ N, 64.7∘ W) in the subtropical
North Atlantic, which highlights some high temporal resolution features in
the penetration of tritium into and ingrowth of 3He within the main
thermocline and intermediate waters at one location.
A time series of tritium (upper) and helium isotope measurements in
the vicinity of Bermuda (North Atlantic). Tritium values have been
decay-corrected to a common time (1 January 1997). White dots indicate
sampling depths and times.
Perhaps the most notable features of the oceanic distribution of the helium
isotope ratio anomaly are the large tongues emanating from mid-ocean ridges
and other volcanic edifices on the sea floor (see the map of the helium
isotope ratio anomaly at 2500 m depth in Fig. 8), driven by the roughly
order-of-magnitude higher 3He/4He ratio in the earth's mantle
compared to the atmosphere (Clarke et al., 1969; Kurz and Jenkins, 1981; Kurz
et al., 1982; Lupton and Craig, 1975). It was in fact the initial discovery
(Clarke et al., 1969) that sparked continued interest in the oceanic
distribution of helium isotopes. In contrast, one sees a different pattern
deeper down (4000 m, in Fig. 9), where one sees the relatively
3He-impoverished bottom waters flowing northward into the abyssal
Pacific. The ongoing survey of deep helium features on both basin and
regional scales continues today, particularly in support of “flux gauge”
studies of other trace elements and metals influenced by seafloor
hydrothermal processes (e.g., Jenkins et al., 2018a; Resing et al., 2015;
Roshan et al., 2016). These are based on recent model-based estimates of the
global flux of hydrothermal 3He, which center around
550 mol yr-1 (Bianchi et al., 2010; Holzer et al., 2017; Schlitzer,
2016). This estimate can be usefully compared to the expected global flux of
tritiugenic 3He. The global tritium production by atmospheric
nuclear weapons tests has been estimated to be of order 3 GCi (Weiss and
Roether, 1980, corrected from 1972 to 1963) to 5 GCi (Michel, 1976). Given
that the bulk of the tritium “impulse” entered the hydrologic system and
subsequently the oceans within a decade or so, one can argue that the
production rate of tritiugenic 3He was of order
3000 mol yr-1 in the mid-1970s. By the mid-1990s, this would be of
order 1000 mol yr-1. Separating the two “types” of 3He
(tritiugenic vs. primordial) in the Northern Hemisphere, where the bulk of
the tritium delivery occurred (Doney et al., 1992; Weiss and Roether, 1980),
is relatively simple in that the former appears largely at the sea surface,
and the latter is concentrated in older, deeper waters. The separation in the
Southern Hemisphere is not so simple.
A map of δ3He values at approximately 2500 m depth.
The values plotted are simply an average of all measurements within a
1∘ square between 2250 and 2750 dbar. Depths shallower than 2500 m
are masked in gray, and sampling locations are indicated by light gray dots.
A map of δ3He values at approximately 4000 m depth.
The values plotted are simply an average of all measurements within a
1∘ square between 3750 and 4250 dbar. Depths shallower than 4000 m
are masked in gray, and sampling locations are indicated by light gray dots.
Data availability
Information about the underlying dataset can be found in
Sect. 2.5.
Contributors and pioneers
This dataset represents the hard work over many decades of numerous
individuals that are not included in the authorship list of this paper. We
list their names and affiliations at the time of their contributions in
Table 3. The list focuses on those who made the measurements rather than
those who may have used the data. We apologize if there are others that we
may have missed in this list.
Contributing analysts that are not authors on this
paper.
Arnold E. BainbridgeUCSD, La Jolla, CA, USAReinhold BayerU. Heidelberg, Heidelberg, GermanyFriedrich BegemannU. Chicago, Chicago, IL, USAUlrich BeyerleETH, Zurich, SwitzerlandWallace S. BroeckerLDEO, Pallisades, NY, USAMartin ButzinUniversity of Bremen, Bremen, GermanyWilliam Brian ClarkeMcMaster University, Hamilton, ON, CanadaK. O. DockinsUCSD, La Jolla, CA, USAH. Gorman DorseyRSMAS, Miami, FL, USAEric ErikssonIMS, Stockholm, SwedenElise FourréCEA-Saclay, FranceBruno J. GilettiLDEO, Pallisades, NY, USAAristid von GrosseRITU, Philadelphia, PA, USAJ. R. HarriesAustralian AEC, Sutherland, NSW, AustraliaT. KajiKyushu University, Fukuoka, JapanSheldon KaufmanU. Chicago, Chicago, IL, USAJ. Laurence KulpLDEO, Pallisades, NY, USAWillard F. LibbyU. Chicago, Chicago, IL, USADempsey E. Lott IIIWHOI, Woods Hole, MA, USAAndrea LudinLDEO, Pallisades, NY, USALiliane MerlivatSorbonne University, Paris, FranceRobert MichelUCSD, La Jolla, CA, USAYasuo MiyakeGRA, Tokyo, JapanKarl-Otto MunnichU. Heidelberg, Heidelberg, GermanyAlfred O. NierU. Minnesota, Minneapolis, MN, USAMasami NonakaIPRC & SOES, Tokyo, JapanHans Göte ÖstlundRSMAS, Miami, FL, USAClare F. PostlethwaiteNOC-SOES, Southampton, UKPaul D. QuayUniversity of Washington, Seattle, WA, USARachel S. H. R. StanleyWHOI, Woods Hole, MA, USASheila StarkNOC-SOES, Southampton, UKReiner SteinfeldtIUP, University of Bremen, GermanyHans E. SuessUCSD, La Jolla, CA, USAJurgen SűltenfussIUP, University of Bremen, GermanyNaoto TakahataORI, University of Tokyo, Tokyo, JapanA. TamulyUniversity of Quebec, Rimouski, PQ, CanadaC. B. TaylorINS, Lower Hutt, New ZealandZafer TopRSMAS, Miami, FL, USATom TorgersenWHOI, Woods Hole, MA, USAKim A. Van ScoyRSMAS, Miami, FL, USACarolyn WalkerWHOI, Woods Hole, MA, USAWolfgang WeissU. Heidelberg, Heidelberg, GermanyPeter M. WilliamsUCSD, La Jolla, CA, USA
We also would like to recognize that the ability to make the measurements
presented in this dataset was a consequence of the pioneering work of more
than a few inventive and talented individuals. While space does not permit
mentioning them all here, we felt it appropriate to highlight a pair of
pioneering scientists who conducted landmark studies on ocean tritium and
3He measurements.
W. Brian Clarke (1937–2002)
Although not the first to measure 3He/4He in the environment
(that was done by Aldrich and Nier, 1948), Clarke made the first reported
helium isotope measurements in seawater (Clarke et al., 1969). He made his
first measurements using a modified single stage magnetic sector, single
collector mass spectrometer to a precision of about 2 %. Clarke developed
the first compact all-metal branch tube mass spectrometer specifically
designed to make 3He/4He measurements ultimately to a precision
of 0.1 % to 0.2 %. At the time, conventional wisdom dictated that
such measurements (let alone precision measurements) were not
possible with a single stage magnetic sector instrument for such high
(106) abundance ratios, but Clarke forged ahead anyway. He initially
constructed two instruments in the early 1970s, using one at McMaster
University in Hamilton, Ontario, Canada, and setting the other machine up at
the Scripps Institute of Oceanography in La Jolla, CA, USA, for Harmon Craig
and John Lupton. These instruments were used in support of the GEOSECS
program and subsequently for a wide variety of other research projects. One
of his students (William J. Jenkins) moved to the Woods Hole Oceanographic
Institution in Woods Hole, MA, USA, where he extended Clarke's design to
construct three other instruments. A post-doctoral investigator from his
laboratory (Zafer Top) moved to RSMAS at the University of Miami and
constructed a similar machine. Clarke also collaborated with a UK mass
spectrometer company to make a commercially produced mass spectrometer
available to the global scientific community.
In his early career, Clarke contributed to the study of meteorites and
nuclear physics using isotope mass spectrometry. Beginning in 1969 Clarke
published a series of ground-breaking papers on 3He/4He
measurements in seawater and lakes (Clarke et al., 1969, 1970; Clarke and
Kugler, 1973; Craig and Clarke, 1970; Craig et al., 1975; Jenkins and
Clarke, 1976; Top and Clarke, 1983; Torgersen and Clarke, 1985). He
contributed research to geology, hydrology, limnology, nuclear physics,
medicine, and other disciplines and was active until 2002 publishing on
3He-related evidence for and against cold fusion (Clarke, 2001; Clarke
and Oliver, 2003; Clarke et al., 2001).
In addition to developing a mass spectrometer capable of measuring
3He/4He ratios to order 0.1 % on sub-nanomolar gas samples,
Clarke also created a method to measure environmental levels of tritium
(3H) in water samples by the 3He regrowth technique
(Clarke et al., 1976), which has become the de facto state of the art in low-level tritium measurements. In addition to being
intrinsically simpler than the traditional low-level method (which involved
electrolytic enrichment combined with low-level proportional gas counting),
this method has proved to be more precise (by more than a factor of 4) and
extended the detection limit to lower levels (by as much as an order of
magnitude) (Bayer et al., 1989; Jenkins et al., 1983; Lott and Jenkins,
1998).
Clarke was inventive and ingenious in the laboratory with a remarkable
ability to recognize opportunities where no one else could and to pursue
them to ultimate success. He was an accomplished glass blower and
constructed vacuum lines and research apparatuses from scratch using many
different kinds of glass (see Fig. 10). Clarke kept unusual work hours when
not teaching, generally arriving at the laboratory after lunchtime and
toiling into the night. Working with him was a delight due to his good
nature and whimsical sense of Irish humor but sometimes challenging because
he was an inveterate prankster.
W. Brian Clarke, working on a high vacuum helium extraction
apparatus (early 1970s).
H. Göte Östlund (1923–2016)
Östlund was a pioneer in US ocean tracer measurements,
establishing a world-class, low-level counting laboratory dedicated to the
measurement of tritium and radiocarbon at the University of Miami. He made
distinguished contributions to ocean, atmosphere, and groundwater sciences,
in particular to the understanding of the timescales of the transport of fluids
through these systems. Östlund had a life-long devotion to the
high-quality measurement of radioactive species. He received a BS in
chemistry in 1949 and a PhD in chemistry in 1958. Both were from the
University of Stockholm. Between 1959 and 1961 Östlund developed the
electrolytic enrichment of tritium and deuterium for low-level environmental
tritium measurements by gas proportional counting at the Radioactive Dating
Laboratory of the Swedish Geological Survey. In the early 1960s, he came to
the Rosenstiel School of the University of Miami. At the Rosenstiel School,
he built a world-class tritium and radiocarbon counting laboratory that set
new standards for low-level counting. His laboratory also processed the
samples rapidly, and he generously shared his data with colleagues. As a
result, relatively routine collection and analysis of large quantities of
samples in a timely manner enabled oceanographers to use the tracer data to
gain new insights into the timescales of oceanographic processes. His work
paved the way for the acceptance of the next generation of tracer
oceanographers, those measuring tritium and helium-3 by mass spectrometry
and those measuring the chlorofluorocarbons.
He played a key role in the creation and execution of early global ocean
survey programs. He developed electrolytic enrichment techniques for
low-level environmental tritium measurements by gas proportional counting
(see Fig. 11).
Östlund was a member of the scientific steering committee for the
Geochemical Ocean Sections Study (GEOSECS), which was the first global-scale
survey of chemical, isotopic, and radiochemical tracers in the ocean
(1972–1978). He produced the first large-scale, high-quality mapping of the
distribution of tritium in the oceans, which opened oceanographers' eyes to
the dynamic and rapid penetration of bomb-produced tracers into the deep
ocean.
H. Göte Östlund preparing a gas sample for low-level
counting analysis (mid-1960s).
Östlund published over 100 papers in peer-reviewed journals on
a wide range of subjects. Although his early interests focused on many areas
including atmospheric transport, they quickly extended to the hydrologic
cycle and the ocean for which he applied radioactive tracers to a spectrum of
scientific problems. As a student, he participation in the discovery of the
anaesthetic Xylocain. Soon after coming to Miami, he used tritium to show
that evaporation from the ocean is the major energy source for hurricanes.
To collect samples he even flew into the eye of a hurricane. He and a
colleague were the first to use tritium data to show that vertical mixing in
the upper layers of the open ocean was an order of magnitude smaller than
predicted by mass balance and theory. This was corroborated 20 years
later by other investigators using new techniques. A major interest of his
was the Arctic Ocean. There he quantified the contributions from ice melt,
runoff, and precipitation to the freshwater budget. This budget plays a
critical role in the global overturning circulation, which is the leading
candidate for modulating decadal to centennial climate.
Östlund was involved in the planning and implementation and served on the
scientific steering committees of early global change programs: Geochemical
Ocean Sections (GEOSECS), which was the first global-scale survey of
chemical, isotopic, and radiochemical tracers in the ocean (1972–1978),
followed in the 1980s by Transient Tracers in the Oceans (TTO). The data his
laboratory produced and collected under the auspices of these programs have
furthered our understanding of the timescales of ocean processes. For
example, the data have been used to estimate the flux of anthropogenic
carbon dioxide into the ocean, the rate of exchange between the atmosphere
and ocean, and rates of deep-water formation. He produced the first
large-scale, high-quality mapping of the distribution of tritium in the
ocean, which opened a new vista on the dynamic and rapid penetration of
bomb-produced tracers into the deep western North Atlantic Ocean. Östlund's
leadership as a member and coordinator of the scientific advisory committee
for GEOSECS and TTO and his vision and credibility in seeing that an
accelerator mass spectrometry facility for 14C analysis was established
in the USA – had a large influence on ocean science. The big
oceanographic programs of the past 50 years (GEOSECS through WOCE, CLIVAR,
and GO-SHIP) have provided platforms for obtaining large quantities of high-quality tracer data.
Östlund was soft-spoken and gentle in demeanor and generous with his time,
advice, and data. He set an example and benchmark for subsequent generations
of tracer geochemists for responsibility, honesty, and fairness.
Author contributions
WJJ is responsible for most of the writing of this
article, along with preparation of the figures and assembly and quality control of the
data in various formats. Numerous co-authors provided useful ideas,
discussion, and critical review of the manuscript, including SCD, RK, WR, and
RN. Several authors pointed out and provided missing data, including PJB, RK,
BK, and MR. MF provided early compilations of the data. RF provided helpful
background information on H. Göte Östlund.
Competing interests
The authors declare that they have no conflict of
interest.
Acknowledgements
This synthesis work was funded under the auspices of a U.S. National Science
Foundation grant number OCE-1434000. Financial support for the actual
measurements came from a wide variety of different research grants from many
agencies in many countries, far too numerous to list here. William J. Jenkins is grateful to a number of US funding sources, most notably the
National Science Foundation, NOAA, DOE, and ONR.
Review statement
This paper was edited by Giuseppe M. R. Manzella and reviewed by two anonymous referees.
ReferencesAldrich, L. T. and Nier, A. O.: The occurrence of 3He in natural
sources of helium, Phys. Rev., 74, 1590–1594, 1948.
Bainbridge, A. E., Sandoval, P., and Suess, H. E.: Natural tritium
measurements by ethane counting, Science, 134, 552–553, 1961.
Bainbridge, A. E., Östlund, H. G., Craig, H., Broecker, W. S., and
Spencer, D. W.: GEOSECS Atlantic, Pacific, and Indian Ocean Expeditions:
Shore-based data and graphics, GEOSECS ATLAS, National Science Foundation,
Washington, D.C., USA, 1987.Bayer, R., Schlosser, P., Bonisch, G., Rupp, H., Zaucker, F., and Zimmek, G.:
Performance and blank components of a mass spectrometric system for routine
measurement of helium isotopes and tritium by 3He ingrowth method,
Sitzungberichte der Heidelberger Akademie der Wissenschaften,
Mathematisch-naturwissenschaftliche Klasse, 5, 241–279, 1989.
Bianchi, D., Sarmiento, J. L., Gnanadesikan, A., Key, R. M., Schlosser, P.,
and Newton, R.: Low helium flux from the mantle inferred from simulations of
oceanic helium isotope data, Earth Planet. Sc. Lett., 297, 379–386, 2010.
Broecker, W. S., Sutherland, S. C., and Smethie, W. M.: Oceanic radiocarbon:
separation of the natural and bomb components, Global Biogeochem. Cy., 9,
263–288, 1995.
Brown, K., Dingley, K. H., and Turteltaub, K. W.: Accelerator mass
spectrometry for biomedical research, Method. Enzymol., 402, 423–443, 2005.
Cameron, J. F.: Radioactive dating and methods of low-level counting,
Proceedings of “Radioactive Dating and Methods of Low-Level Counting”,
International Atomic Energy Agency, Monaco, 2–10 March 1967, 543–574, 1967.
Chiarappa-Zucca, M. L., Dingley, K. H., Roberts, M. L., Velsko, C. A., and
Love, A. H.: Sample preparation for quantification of tritium by acclerator
mass spectrometry, Anal. Chem., 74, 6285–6290, 2002.Clarke, W. B.: Search for 3He and 4He in Arata-Style
Palladium Cathods I: a negative result, Fusion Sci. Technol., 40, 147–151,
10.13182/FST01-A189, 2001.
Clarke, W. B. and Kugler, G.: Dissolved helium in groundwater: a possible
method for uranium and thorium prospecting, Econ. Geol., 68, 243–251, 1973.Clarke, W. B. and Oliver, B. M.: Response to “Comments on `Search for
3He and 4He in Arata-style palladium cathodes I: a
negative result' and `Search for 3He and 4He in
Arata-style palladium cathodes II: evidence for tritium production”', Fusion
Sci. Technol., 43, 135–136, 2003.Clarke, W. B., Beg, M. A., and Craig, H.: Excess 3He in the sea:
evidence for terrestrial primordial helium, Earth Planet. Sc. Lett., 6,
213–220, 1969.
Clarke, W. B., Beg, M. A., and Craig, H.: Excess Helium 3 at the North
Pacific GEOSECS station, J. Geophys. Res., 75, 7676–7678, 1970.Clarke, W. B., Jenkins, W. J., and Top, Z.: Determination of tritium by
spectrometric measurement of 3He, Int. J. Appl. Radiat. Is., 27,
515–525, 1976.Clarke, W. B., Oliver, B. M., McKubre, M. C. H., Tanzella, F. L., and
Tripodi, P.: Search for 3He and 4He in Arata-Style
Palladium Cathodes II: Evidence of tritium production, Fusion Sci. Technol.,
40, 152–167, 10.13182/FST01-A190, 2001.
Cornog, R. and Libby, W. F.: Production of radioactive hydrogen by neutron
bombardment of boron and nitrogen, Phys. Rev., 59, p. 1046, 1941.Craig, H. and Clarke, W. B.: Oceanic 3He: contribution from
cosmogenic tritium, Earth Planet. Sc. Lett., 9, 45–48, 1970.Craig, H., Clarke, W. B., and Beg, M. A.: Excess 3He in deep water
on the East Pacific Rise, Earth Planet. Sc. Lett., 26, 125–132, 1975.
Currie, L. A., Libby, W. F., and Wolfgang, R. L.: Tritium production by high
energy protons, Phys. Rev., 101, 1557–1563, 1956.Doney, S. C. and Jenkins, W. J.: Ventilation of the deep western boundary
current and abyssal Western North Atlantic: Estimates from tritium and
3He distributions, J. Phys. Oceanogr., 24, 638-659, 1994.
Doney, S. C., Glover, D. M., and Jenkins, W. J.: A model function of the
global bomb-tritium distribution in precipitation, 1960–1986, J. Geophys.
Res., 97, 5481–5492, 1992.
Dorsey, H. G. and Peterson, W. H.: Tritium in the Arctic Ocean and East
Greenland Current, Earth Planet. Sc. Lett., 32, 342–350, 1976.Dreisigacker, E. and Roether, W.: Tritium and 90Sr in North
Atlantic surface water, Earth Planet. Sc. Lett., 38, 301–312, 1978.
Fine, R. A. and Östlund, H. G.: Source function for tritium transport
models in the Pacific, Geophys. Res. Lett., 4, 461–464, 1977.
Fine, R. A., Reid, J. L., and Östlund, H. G.: Circulation of tritium in
the Pacific Ocean, J. Phys. Oceanogr., 11, 3–14, 1981.
Fine, R. A., Peterson, W. H., and Östlund, H. G.: The penetration of
tritium into the tropical Pacific, J. Phys. Oceanogr., 17, 553–564, 1987.Fuchs, G., Roether, W., and Schlosser, P.: Excess 3He in the ocean
surface layer, J. Geophys. Res., 92, 6559–6568, 1987.German, C. R., Casciotti, K. L., Dutay, J.-C., Heimburger, L. E., Jenkins, W.
J., Measures, C., Mills, R. A., Obata, H., Schlitzer, R., Tagliabue, A.,
Turner, D. R., and Whitby, H.: Hydrothermal impacts on trace element and
isotope ocean biogeochemistry, Philos. T. Roy. Soc. A, 374, 20130035,
10.1098/rsta.2016.0035, 2016.
Glagola, B. G., Phillips, G. W., Marlow, K. W., Myers, L. T., and Omohundro,
R. J.: Low level tritium detection using accelerator mass spectrometry, Nucl.
Instrum. Meth. B, 5, 221–225, 1984.
Grosse, A. V., Johnston, W. M., Wolfgang, R. L., and Libby, W. F.: Tritium in
nature, Science, 113, 1–2, 1951.Holzer, M., DeVries, T., Bianchi, D., Newton, R., Schlosser, P., and
Winckler, G.: Objective estimates of mantle 3He in the ocean and
implications for constraining the deep ocean circulation, Earth Planet. Sc.
Lett., 458, 305–314, 2017.
Israel, G. W.: Messung des Tritium-Jahresganges im Regen 1960–1961 nach
Isotopenanreicherung im Trnnrohr, Z. Naturforschg., 17a, 925–929, 1962.
Jenkins, W. J.: Tritium-helium dating in the Sargasso Sea: a measurement of
oxygen utilization rates, Science, 196, 291–292, 1977.Jenkins, W. J.: 3H and 3He in the Beta Triangle:
Observations of gyre ventilation and oxygen utilization rates, J. Phys.
Oceanogr., 17, 763–783, 1987.
Jenkins, W. J.: Nitrate flux into the euphotic zone near Bermuda, Nature,
331, 521–523, 1988.Jenkins, W. J.: Studying Thermocline Ventilation and Circulation Using
Tritium and 3He, J. Geophys. Res., 103, 15817–15831, 1998.Jenkins, W. J. and Clarke, W. B.: The distribution of 3He in the
western Atlantic Ocean, Deep-Sea Res., 23, 481–494, 1976.Jenkins, W. J. and Doney, S. C.: The Subtropical Nutrient Spiral, Global
Biogeochem. Cy., 17, 1110, 10.1029/2003GB002085, 2003.
Jenkins, W. J. and Rhines, P. B.: Tritium in the deep North Atlantic Ocean,
Nature, 286, 877–880, 1980.
Jenkins, W. J. and Smethie, W. M.: Transient tracers track ocean climate
signals, Oceanus, 39, 29–32, 1996.Jenkins, W. J., Beg, M. A., Clarke, W. B., Wangersky, P. J., and Craig, H.:
Excess 3He in the Atlantic Ocean., Earth Planet. Sc. Lett., 16,
122–130, 1972.Jenkins, W. J., Edmond, J. M., and Corliss, J. B.: Excess 3He and
4He in Galapagos submarine hydrothermal waters, Nature, 272,
156–158, 1978.
Jenkins, W. J., Lott, D. E., Pratt, M. W., and Boudreau, R. D.: Anthropogenic
tritium in South Atlantic bottom water, Nature, 305, 45–46, 1983.
Jenkins, W. J., Lott, D. E. I., German, C. R., Cahill, K. L., Goudreau, J.,
and Longworth, B. E.: The deep distributions of helium isotopes, radiocarbon,
and noble gases along the U.S. GEOTRACES East Pacific zonal transect (GP16),
Mar. Chem., 201, 167–182, 2018a.Jenkins, W. J., Doney, S. C., Fendrock, M. A., Fine, R. A., Gamo, T.,
Jean-Baptiste, P., Key, R. M., Klein, B., Lupton, J. E., Rhein, M., Roether,
W., Sano, Y., Schlitzer, R., Schlosser, P., Swift, J. H.: A comprehensive
global oceanic dataset of discrete measurements of helium isotope and tritium
during the hydrographic cruises on various ships from 1952-10-21 to
2016-01-22 (NCEI Accession 0176626). Version 2.2. NOAA National Centers for
Environmental Information, Dataset, 10.25921/c1sn-9631, 2018b.
Kaufman, S. and Libby, W. F.: The natural distribution of tritium, Phys.
Rev., 93, 1337–1344, 1954.
Kurz, M. D. and Jenkins, W. J.: The distribution of helium in oceanic basalt
glasses, Earth Planet. Sc. Lett., 53, 41–54, 1981.
Kurz, M. D., Jenkins, W. J., and Hart, S. R.: Helium isotopic systematics of
oceanic islands and mantle heterogeneity, Nature, 297, 43–47, 1982.
Libby, W. F.: Atmospheric helium three and radiocarbon from cosmic radiation,
Phys. Rev., 59, 671–672, 1946.Lott, D. E.: Improvements in noble gas separation methodology: a nude
cryogenic trap, Geochem. Geophy. Geosy., 2, 2001GC000202,
10.1029/2001GC000202, 2001.
Lott, D. E. and Jenkins, W. J.: An automated cryogenic charcoal trap system
for helium isotope mass spectrometry, Rev. Sci. Instrum., 55, 1982–1988,
1984.
Lott, D. E. and Jenkins, W. J.: Advances in the analysis and shipboard
processing of tritium and helium samples, International WOCE Newsletter, 30,
27–30, 1998.
Ludin, A., Weppernig, R., Bönisch, G., and Schlosser, P.: Mass
spectrometric measurement of helium isotopes and tritium, Technical Report
No. 98.6, 41 pp., Lamont-Doherty Earth Observatory, Columbia University, New
York, USA, 1998.
Lupton, J. E. and Craig, H.: Excess He-3 in oceanic basalts: evidence for
terrestrial primordial helium, Earth Planet. Sc. Lett., 26, 133–139, 1975.
Lupton, J. E. and Jenkins, W. J.: Evolution of the South Pacific helium plume
over the past 3 decades, Geochem. Geophy. Geosy., 18, 1810–1823, 2017.
Mamyrin, B. A.: Time-of-flight mass spectrometry (concepts, achievements and
prospects), Int. J. Mass Spectrom., 206, 251–266, 2001.
Mamyrin, B. A., Anufriyev, S. G., Kamenskiy, I. L., and Tolstikhin, I. I.:
Determination of the isotopic composition of atmospheric helium, Geochem.
Int., 6, 498–505, 1970.
Michel, R. L.: Tritium inventories of the world oceans and their
implications, Nature, 263, 103–106, 1976.
Michel, R. L. and Suess, H. E.: Bomb tritium in the Pacific Ocean, J.
Geophys. Res., 80, 4139–4152, 1975.
Miyake, Y., Shimada, T., Sugimura, Y., Shigehara, K., and Saruhashi, K.:
Distribution of tritium in the Pacific Ocean, Records of Oceanographic Works
in Japan, 13, 17–32, 1975.
Momoshima, N., Nakamura, Y., and Takashima, Y.: Vial Effect And Background
Subtraction Method In Low-Level Tritium Measurement By Liquid
Scintillation-Counter, Int. J. Appl. Radiat. Is., 34, 1623–1626, 1983.
Östlund, H. G.: The residence time of the freshwater component in the
Arctic Ocean, J. Geophys. Res., 87, 2035–2043, 1982.
Östlund, H. G. and Werner, E.: The electrolytic enrichment of tritium and
deuterium for natural tritium measurements, International Atomic Energy
Agency, Vienna, Austria, 95 pp., 1962.
Östlund, H. G., Dorsey, H. G., and Rooth, C. G.: GEOSECS North Atlantic
Radiocarbon and Tritium Results, Earth Planet. Sc. Lett., 23, 69–86, 1974.
Resing, J. A., Sedwick, P. N., German, C. R., Jenkins, W. J., Moffett, J. W.,
Sohst, B. M., and Tagliabue, A.: Basin-Scale transport of hydrothermal
dissolved metals across the South Pacific Ocean, Nature, 523, 203–206, 2015.Rhein, M., Dengler, M., Sultenfuss, J., Hummels, R., Huttle-Kabus, S., and
Bourles, B.: Upwelling and associated heat flux in the equatorial Atlantic
inferred from helium isotope disequilibrium, J. Geophys. Res.-Oceans, 115,
C08021, 10.1029/2009JC005772, 2010.
Roberts, M. L., Hamme, R. W., Dingley, K. H., Chiarappa-Zucca, M. L., and
Love, A. H.: A compact tritium AMS system, Nucl. Instrum. Meth. B, 172,
262–267, 2000.
Roether, W., Well, R., Putzka, A., and Ruth, C.: Component separation of
oceanic helium, J. Geophys. Res., 103, 27931–27946, 1998.
Roether, W., Vogt, M., Vogel, S., and Sültenfuß, J.: Combined sample
collection and gas extraction for the measurement of helium isotopes and neon
in natural waters, Deep-Sea Res. Pt. I, 76, 27–34, 2013.
Roshan, S., Wu, J., and Jenkins, W. J.: Long-range transport of hydrothermal
dissolved Zn in the tropical South Pacific, Mar. Chem., 183, 25–32, 2016.
Sarmiento, J. L.: A simulation of bomb tritium entry into the Atlantic Ocean,
J. Phys. Oceanogr., 13, 1924–1939, 1983.Schlitzer, R.: Quantifying He fluxes from the mantle using multi-tracer data
assimilation, Philos. T. Roy. Soc. A, 374, 0000-0002-3740-6499,
10.1098/rsta.2015.0288, 2016.Stanley, R. H. R., Jenkins, W. J., Doney, S. C., and Lott III, D. E.: The
3He flux gauge in the Sargasso Sea: a determination of physical
nutrient fluxes to the euphotic zone at the Bermuda Atlantic Time-series
Site, Biogeosciences, 12, 5199–5210,
10.5194/bg-12-5199-2015, 2015.
Top, Z. and Clarke, W. B.: Helium, neon, and tritium in the Black Sea, J.
Mar. Res., 41, 1–17, 1983.
Torgersen, T. and Clarke, W. B.: Helium accumulation in groundwater, 1: an
evaluation of sources and the continental flux of crustal He-4 in the Great
Artesian Basin, Australia, Geochim. Cosmochim. Ac., 49, 1211–1218, 1985.Unterweger, M. P., Coursey, B. M., Schima, F. J., and Mann, W. B.:
Preparation and calibration of the 1978 National Bureau of Standards
tritiated-water standards, Int. J. Appl. Radiat. Is., 31, 611–614, 1980.
Weiss, R. F.: Piggyback sampler for dissolved gas studies on sealed water
samples, Deep-Sea Res., 15, 695–699, 1968.
Weiss, W. M. and Roether, W.: The rates of tritium input to the world oceans,
Earth Planet. Sc. Lett., 49, 435–446, 1980.
Weiss, W. M., Roether, W., and Dreisigacker, E.: Tritium in the North
Atlantic: inventory, input and transfer to the deep water, in: The Behavior
of tritium in the Environment, International Atomic Energy Agency, Vienna,
Austria, 1979.
Young, C. and Lupton, J. E.: An ultratight fluid sampling system using
cold-welded copper tubing., EOS Transactions AGU, 64, p. 735, 1983.