ORNL/CDIAC-152

NDP-088

GLOBAL OCEAN SURFACE WATER PARTIAL PRESSURE OF CO~2~ DATABASE:
MEASUREMENTS PERFORMED DURING 1968--2006

(Version 1.0)

Contributed by

Taro Takahashi and Stewart C. Sutherland

Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY
10964

Date Published: September 2007

Prepared for the Climate Change Research Division

Office of Biological and Environmental Research

U.S. Department of Energy

Budget Activity Numbers KP 12 04 01 0 and KP 12 02 03 0

Prepared by

Alex Kozyr

Carbon Dioxide Information Analysis Center

OAK RIDGE NATIONAL LABORATORY

Oak Ridge, Tennessee 37831-6335

managed by

UT-BATTELLE, LLC

for the

U.S. DEPARTMENT OF ENERGY

under contract DE-AC05-00OR22725

# CONTENTS

List of Figures v

List of Tables v

Abbreviations and Acronyms vii

Abstract ix

1\. INTRODUCTION 1

2\. OBJECTIVE 2

3\. METHODS OF COMPUTATION 2

4\. QUALITY CONTROL 4

5\. DATA SOURSES 5

6\. DATA LISTING 6

7\. HOW TO OBTAIN THE DATA AND DOCUMENTATION 8

8\. ACKNOWLEDGEMENTS 9

9\. REFERENCES 9

# LIST OF FIGURES

1 Location of LDEO master database of sea surface pCO~2~ observations. 2

# 

# LIST OF TABLES

1 List of data contributors to the global surface water pCO~2~ LDEO
database 5

2 Data elements listed in the master data file "LDEO_Database.txt" 6

3 Data elements listed in the metadata file "Metadata.xls" 7

# ABBREVIATIONS AND ACRONYMS

AOML Atlantic Oceanographic and Meteorological Laboratory

CDIAC Carbon Dioxide Information Analysis Center

CLIVAR Climate Variability (Program)

CO~2~ carbon dioxide

CSIRO Australian Commonwealth Scientific and Research Organization

DOE U.S. Department of Energy

FTP file transfer protocol

*f*CO~2~ fugacity of CO~2~

GEOSECS Geophysical Sections Experiment

IGY International Geophysical Year

JGOFS Joint Global Ocean Flux Study

LDEO Lamont-Doherty Earth Observatory

NCAR National Center for Atmospheric Research

NCEP National Centers for Environmental Prediction

NDP numeric data package

NOAA National Oceanic and Atmospheric Administration

NSF National Science Foundation

ORNL Oak Ridge National Laboratory

pCO~2~ partial pressure of CO~2~

PMEL Pacific Marine Environmental Laboratory

SSS sea surface salinity

SST sea surface temperature

VOS Volunteer Observing Ship

WOCE World Ocean Circulation Experiment

# ABSTRACT

Takahashi, T., S.C. Sutherland, and A. Kozyr. 2007. Global Ocean Surface
Water Partial Pressure of CO~2~ Database: Measurements Performed During
1968--2006 (Version 1.0). ORNL/CDIAC-152, NDP- 088. Carbon Dioxide
Information Analysis Center, Oak Ridge National Laboratory, U.S.
Department of Energy, Oak Ridge, Tennessee, 20 pp.

More than 3 million measurements of surface water partial pressure of
CO~2~ obtained over the global oceans during 1968--2006 are listed in
the Lamont-Doherty Earth Observatory (LDEO) database, which includes
open ocean and coastal water measurements. The data assembled include
only those measured by equilibrator-CO~2~ analyzer systems and have been
quality-controlled based on the stability of the system performance, the
reliability of calibrations for CO~2~ analysis, and the internal
consistency of data. To allow re-examination of the data in the future,
a number of measured parameters relevant to pCO~2~ measurements are
listed. The overall uncertainty for the pCO~2~ values listed is
estimated to be ± 2.5 atm on the average.

The data presented in this database include the analyses of partial
pressure of CO~2~ (pCO~2~), sea surface temperature (SST), sea surface
salinity (SSS), pressure of the equilibration, and barometric pressure
in the outside air from the ship's observation system.

The global pCO~2~ data set is available free of charge as a numeric data
package (NDP) from the Carbon Dioxide Information Analysis Center
(CDIAC). The NDP consists of the oceanographic data files and this
printed documentation, which describes the procedures and methods used
to obtain the data.

**Keywords**: carbon dioxide, partial pressure of CO~2~, global carbon
cycle, global ocean, equilibrator-CO~2~ analyzer systems.

# 1. INTRODUCTION

Transfer of CO~2~ between the atmosphere and the oceans is a critical
process of the global carbon cycle and is important for the future of
the earth's climate. During the past decade, about 6 Pg-C yr ^-1^ \[1 Pg
(peta grams) =10^15^ grams = 1 Giga ton\] has been emitted into the
atmosphere from various anthropogenic sources including the combustion
of fossil fuels, cement production, deforestation, land use changes, and
others. On the basis of various independent scientific methods including
changes in oxygen and CO~2~ concentrations in the atmosphere (Keeling et
al. 1996, Bender et al. 2005, Garcia and Keeling 2001), sea-air
differences in CO~2~ partial pressure (Takahashi et al. 2002),
distribution of carbon isotopes (^12^C, ^13^C, and ^14^C) (Quay et al.
2003), inversion of atmospheric CO~2~ distribution data using
atmospheric circulation models (Patra et al. 2005), and various global
carbon cycle models (Sarmiento et al. 2000, Gruber and Sarmiento 2002),
the annual uptake rate of CO~2~ by the oceans has been estimated to be
about 2 Pg-C yr ^-1^ for the past decade. Thus, \~30% of the
anthropogenic CO~2~ emissions are absorbed annually by the oceans, and
\~50% remain in the atmosphere. As a result, the atmospheric CO~2~
concentration is increasing at a mean rate of about 1.5 ppm yr ^-1^ (or
0.4% per year), and the concentration of CO~2~ dissolved in surface
ocean waters is also increasing, causing the acidification of ocean
waters. Accurately documenting changes in the CO~2~ chemistry in ocean
waters over time is therefore important for understanding the fate of
anthropogenic CO~2~ released into the atmosphere as well as charting the
future course of atmospheric CO~2~ levels that would affect the earth's
climate.

Carbon dioxide molecules react chemically with water to form bicarbonate
(HCO~3~^-^) and carbonate (CO~3~^=^) ions, neither of which communicate
with the overlying air. Only about 0.5% of the total CO~2~ molecules
dissolved in seawater communicate with air via gas exchange across the
sea surface. This quantity is called the partial pressure of CO~2~
(pCO~2~), which represents the CO~2~ vapor pressure. The seawater pCO~2~
depends on the temperature, the total amount of CO~2~ dissolved in
seawater, and seawater pH. Over the global ocean, it varies from about
100 atm to 1000 atm (1atm = 10^-6^ atm). When seawater pCO~2~ is less
than the atmospheric pCO~2~ (presently about 370 atm), seawater takes up
CO~2~ from the overlying air; when it is greater than the atmospheric
pCO~2~, it emits CO~2~ to the air. The rate of transfer of CO~2~ across
the sea surface is estimated by: (sea-air CO~2~ flux) = (transfer
coefficient) x (sea-air pCO~2~ difference). The transfer coefficient
depends primarily on the degree of turbulence near the interface, and is
commonly expressed as a function of wind speed. Since the time-space
variation for atmospheric pCO~2~ is much smaller than that for surface
ocean water pCO~2~, the magnitude of sea-air CO~2~ flux is governed
primarily by seawater pCO~2~. Therefore, the inter-annual and seasonal
variability for surface water pCO~2~ is of particular interest.

The atmospheric CO~2~ concentrations observed at a number of locations
over the globe is summarized in GLOBALVIEW-CO2 (2006) and TRENDS ON LINE
(2006). On the other hand, no single data file for surface water pCO~2~
that includes long-term and global coverage has been made accessible to
the general public. About 20 years ago, we started to assemble a global
surface water pCO~2~ data for time-space variability studies for the
global oceans using the observations made by the Lamont-Doherty Earth
Observatory (LDEO) group. Many investigators from other institutions
contributed data to the database for the first publication on the global
ocean pCO~2~ and sea-air CO~2~ flux (Takahashi et al. 1997), which was
based on about 0.25 million pCO~2~ measurements; the second publication
(Takahashi et al. 2002) was based on about a million measurements. The
LDEO database now consists of more than 3 million pCO~2~ measurements
(Fig. 1) plus a number of other measured supporting parameters. A paper
summarizing these observations has been submitted for publication in the
Deep Sea Research (Takahashi et al. in review). A subset of this
database is used for estimating the sea-air CO~2~ flux from coastal
waters surrounding North America (Chavez and Takahashi 2007). Mindful of
the increasing importance of CO~2~ studies for future global welfare,
LDEO is sharing this data file widely with the global research
communities and the public through the Carbon Dioxide Information
Analysis Center (CDIAC) data archive.

![](media/image1.jpeg){width="6.4944444444444445in"
height="3.2472222222222222in"}

**Fig. 1. Location of LDEO master database of sea surface pCO~2~
observations.**

# 2. OBJECTIVE

Modern investigation of ocean water pCO~2~ started during the
International Geophysical Year (IGY), 1957--1960, with the introduction
of infrared CO~2~ gas analyzer and gas-water equilibrator aboard
oceanographic research vessels (Takahashi 1961, Keeling et al. 1965,
Broecker and Takahashi 1966). Combined with high-accuracy CO~2~-air-gas
mixtures made available for the calibrations of the analyzers at sea,
the quality of seawater pCO~2~ data was greatly improved from that
obtained in the pre-World War II era. During major oceanographic
programs that took place after IGY, the CO~2~ analyzers and
equilibrators have been steadily improved to give more frequent
observations and better accuracy, although the principles of the
measurement remained essentially unchanged. Computers used for system
control and data logging contributed significantly to the data quality.
The objective of this database is to assemble high-quality pCO~2~ data
obtained using the equilibrator-analyzer method, and to reprocess the
data using a standardized method of computation, that will be described
below. Therefore, the pCO~2~ values listed in this database may differ
from the original listings prepared by respective investigators.

# 3. METHODS OF COMPUTATION

The seawater pCO~2~ data listed in LDEO database are based on direct
measurements of seawater pCO~2~ made using equilibrator-CO~2~ analyzer
systems. Many of the data listed are from semi-continuous pCO~2~ systems
with flow-through water; many others are measurements for discrete water
samples made at hydrographic stations along with measurements for other
chemical and physical properties. Although different types of
equilibrators (e. g., shower type, bubbling type, membrane type, and
rotating disks in flow-through or closed circulation systems) and CO~2~
gas analyzers (non-dispersive infrared analyzers and gas chromatographs
of various designs) were employed, the results from different systems
are accepted as long as analyzers were properly calibrated using
validated CO~2~-air gas mixtures and the carrier gas was equilibrated
with seawater samples. Because of the diversity of methods used, it is
impossible to present details of the method used by each contributing
research group. Detailed methodology may be obtained directly from the
investigators listed in Table 1, or from the CDIAC reports for specific
expeditions.

It is important to point out that the methods used for computing CO~2~
concentrations in equilibrated gas have been varied among groups. For
example, some groups computed a least-square fit of readings for three
or more standard gas mixtures to a quadratic equation and used it to
calculate concentrations in samples. Some groups used four or five
standard gas mixtures for calibrations, and fitted the data to a 4^th^
order polynomial equation. And some groups used an output from
linearization circuits of infrared analyzer, and linearly regressed
three or more standard gas readings to obtain sample CO~2~
concentrations. The outputs from a gas chromatograph are a linear
function of CO~2~ concentration, and hence a linear regression was used
for calibration. These different data reduction methods yield CO~2~
concentrations varying ± 1.5 ppm (or ± 1.5 atm in pCO~2~). However, we
did not recompute the CO~2~ values using a single uniform algorithm but
instead, accepted CO~2~ concentration values as reported to us. Since
different analyzers and different numbers of standard gas mixtures were
used by respective groups, no single uniform data reduction scheme can
be applied, and hence we relied on the judgment of each group for
selecting the data reduction scheme most suited for their operational
modes and skills. Measurements that were made using only one calibration
gas mixture were judged unreliable and were not included in this
database.

Using the reported CO~2~ concentration values, the pCO~2~ value in
sample seawater at the equilibration temperature, (pCO~2~)~eq~, has been
recomputed with the relationship:

(pCO~2~)~eq~ = V~co2~ (P~eq~ -- P~water~),

where V~co2~ is the mole fraction concentration of CO~2~ in carrier gas
(V~CO2~ is same as X~CO2~, which is often used in literature, and these
qualities may be used interchangeably); P~eq~ is the total pressure of
gas in the equilibrator; and P~water~ is the equilibrium water vapor
pressure at temperature of equilibration, T~eq~, and salinity. Since
some equilibrators were operated open to the room air, P~eq~ values may
be equal to the ship's interior pressure or to the barometric pressure
outside the ship depending on the location of the equilibrator. When an
equilibrator is located in an enclosed shipboard laboratory and is open
to the room air, P~eq~ is the ambient pressure in the laboratory. While
an equilibrator operated in an enclosed space, only the barometric
pressure at sea surface was reported in some data sets, but not P~eq~.
In such cases, P~eq~ is assumed to be the reported barometric pressure
at sea surface plus 3 mb, that represents an overpressure normally
maintained inside a ship. This correction increases the (pCO~2~)~sw~
value by about 1 atm. When the pressure was not reported, we used the
climatological value in the nearest box from the National Centers for
Environmental Prediction/National Center for Atmospheric Research
(NCEP/NCAR) Reanalysis II Project file for the month of the observation.
The pCO~2~ at in-situ seawater temperature is computed using an
integrated form of the temperature effect for isochemical seawater, ( ln
pCO~2~/ T) ~Sal,\ Alk,\ TCO2~ (Takahashi et al., 1993):

(pCO~2~)~sw~ \@T~in\ situ~ = \[(pCO~2~)~sw~ @ T~eq~\] Exp{0.0433
(T~in\ situ~ -- T~eq~) − 4.35 x 10^-5^ \[(T~in\ situ~)^2^ -- (T~eq~)^2^
\] }

where the "sw" and "eq" indicate the in situ and equilibrator conditions
respectively. Throughout the computation, CO~2~ gas is assumed to behave
as an ideal gas that mixes with air and water vapor ideally. Although
CO~2~ fugacity is used in a number of published papers and data reports,
we refrained from using the fugacity since it is computed differently
from an investigator to another. Although we do not list the sea-air
pCO~2~ differences in this report, we recommend the formula below for
the computation of atmospheric pCO~2~ and the corresponding value for
sea-air pCO~2~ difference.

(pCO~2~)~air~ = (V~CO2~)~air~ (P~baro~ -- P~sw~)

> where P~baro~ is the barometric pressure at sea surface, and P~sw~ is
> the equilibrium water vapor pressure at the temperature and salinity
> for mixed layer water. The subscript "air" indicates the value for
> atmosphere samples.
>
> The sea-air pCO~2~ difference, pCO~2~, is then computed using:

pCO~2~ = (pCO~2~)~sw~ -- (pCO~2~)~air~

Since CO~2~ is assumed to be an ideal gas for both (pCO~2~)~sw~ and
(pCO~2~)~air~, the small effects of non-ideality should cancel due to
differencing for pCO~2~. Positive pCO~2~ values indicate that the sea
is a source for atmospheric CO~2~, whereas negative values indicate that
the sea is a sink.

Values for the fugacity of CO~2~ in seawater, *f*CO~2~, have been
submitted to us by some investigators. However, often the fugacity is
not clearly defined as to whether only the non-ideality arising from
CO~2~-CO~2~ molecular interactions is considered and/or that from
CO~2~-H~2~O interactions is also included. Because of these ambiguities,
we have chosen not to list *f*CO~2~ values. Since the mole fraction
concentrations of CO~2~ in equilibrated gas samples are also included in
the reported data, we have computed pCO~2~ using the reported
temperature, pressure, and other data and listed in this report using
the ideal gas law as explained earlier. Since *fCO~2~* values are always
smaller than the corresponding pCO~2~ values by 1 to 2 atm and the
differences are large enough with respect to the precision of
measurements and the mean global sea-air pCO~2~ difference of about 10
atm, they should not be used interchangeably with pCO~2~.

**4. QUALITY CONTROL**

Determination of surface water pCO~2~ requires measurements for a number
of parameters in addition to the concentration of CO~2~ in the carrier
gas equilibrated with seawater. With the broad range of data sources and
continued evolution of the measurement systems, it has not been possible
to ensure that the observations contain all the necessary data elements
with desired precisions. In some cases, pCO~2~ or *f*CO~2~ was reported
without V~CO2~, sometimes with the pressure at the time of
equilibration, sometimes not. Some files contained only the sea surface
temperature and the pCO~2~ at that temperature, but not the temperature
and pCO~2~ at equilibration. Ideally, the incoming file should contain
the dried concentration of CO~2~ in a parcel of air in equilibrium with
seawater (V~CO2~), the temperature at the time of equilibration, and the
equilibration pressure. When the pressure was not reported, we used the
climatological value in the nearest box from the NCEP/NCAR Reanalysis II
Project file for the month of the observation. We accepted data points
that contained pCO~2~ and sea surface temperature with or without the
pressure.

Field data obtained in earlier years do not necessarily have all the
required supporting measurements. For example, the temperatures of
equilibration and water samples were recorded by hand at intervals of a
few to several hours, and hence these values are often interpolated
linearly with time between measurements. The salinity was measured only
at hydrographic stations, and these values were interpolated between
stations. When salinity was not measured during some expeditions,
climatological values were assigned. Some data were unrecoverable and
lost as a result of changes in computer systems (hardware and software).
For the past decade, computer controlled systems for underway surface
water pCO~2~ measurements have been deployed widely, and more complete
high quality data sets have been obtained. In constructing this data
file, we exercised our personal judgment for accepting and rejecting
data, especially those collected in earlier years. For more recent data
sets, water flow rates through the equilibrator and the temperatures of
equilibrator water are recorded for each pCO~2~ measurement. They often
served as important criteria for identifying satisfactory operation of
the equilibrator. Measurements made at reduced or stopped water flow
conditions were rejected, as were those made at unusually rapid changes
in the temperature of the water in an equilibrator. CO~2~ gas analyzers
are commonly calibrated using three or more gas mixtures of different
CO~2~ concentrations. Those measurements made using only a single
calibration gas mixture are subject to unspecified uncertainties, and
hence are rejected.

All data points have been examined individually as they were integrated
into this database. While not perfect, we have tried to edit out obvious
problems, erring on the side of leaving in questionable ones.
Considering differences in equilibrator designs, calibration methods and
some interpolated parameters, we estimate that the uncertainty of the
pCO~2~ data presented in this data file is about ± 2.5 atm on the
average.

Seawater pCO~2~ values that were computed using the alkalinity, total
CO~2~ concentration, and pH data are not included in this data file
because of their large uncertainties and potential biases resulting from
different dissociation constants of carbonic, boric and other acids used
for the computations.

During many cruises, atmospheric CO~2~ concentrations were measured
concurrently with surface water pCO~2~. However, we suspect that many of
these measurements were contaminated by local sources (such as ship's
exhausts). Since atmospheric CO~2~ concentrations vary from one air mass
to another, especially in the northern hemisphere, distinguishing local
contamination from natural variability is difficult. Hence, we decided
to omit the atmospheric CO~2~ data from this file. We recommend that the
atmospheric CO~2~ concentration data listed in the GLOBALVIEW-CO2 for
computing the sea-air pCO~2~ difference.

**5. DATA SOURCES**

The LDEO database lists more than 3 million surface ocean pCO~2~
observations made since 1968. A large portion of the data is composed of
observations from the continuous underway systems, such as those used
aboard the National Science Foundation icebreakers *Nathaniel B. Palmer*
and *Laurence B.* *Gould* operating primarily in the Southern Ocean, and
the research ships operated by the Atlantic Oceanographic and
Meteorological Laboratory and the Pacific Marine Environmental
Laboratory of the National Oceanic and Atmospheric Administration. The
database also includes the observations made during a number of major
national and international oceanographic programs such as Geophysical
Sections Experiment (GEOSECS), Joint Global Ocean Flux Study (JGOFS),
World Ocean Circulation Experiment (WOCE), Climate Variability (CLIVAR)
Repeat Hydrography Project, Volunteer Observing Ships (VOS) Project and
others, which were supported by the National Science Foundation,
National Oceanic and Atmospheric Administration, and Department of
Energy. A significant number of data have been contributed by
international colleagues from many countries including Japan, Germany,
France, UK, Iceland, Australia, Canada, the Netherlands, Norway, and
others. Table 1 lists the major contributors for the database.

**Table 1**. **List of data contributors to the global surface water
pCO~2~ LDEO database.**

+----------------+------------------------------------------+---------+
| **PI           | **Institution**                          | **Co    |
| name^\*^**     |                                          | untry** |
+----------------+------------------------------------------+---------+
| Thorarinn S.   | Marine Research Institute and University | Iceland |
| Arnarson       | of Iceland                               |         |
+----------------+------------------------------------------+---------+
| Dorothee C. E. | School of Environmental Sciences,        | UK      |
| Bakker         | University of East Anglia                |         |
+----------------+------------------------------------------+---------+
| Nicholas R.    | Bermuda Institute of Ocean Sciences      | Bermuda |
| Bates          |                                          |         |
+----------------+------------------------------------------+---------+
| Richard        | Bjerknes Centre for Climate Research,    | Norway  |
| Bellarby       | University of Bergen                     |         |
+----------------+------------------------------------------+---------+
| Wei-Jun Cai    | University of Georgia                    | USA     |
+----------------+------------------------------------------+---------+
| Francisco      | Monterey Bay Aquarium Research Institute | USA     |
| Chavez         |                                          |         |
+----------------+------------------------------------------+---------+
| David W.       | Lamont-Doherty Earth Observatory,        | USA     |
| Chipman^\*\*^  | Columbia University                      |         |
+----------------+------------------------------------------+---------+
| Bruno Delille  | Universite de Liege, Liege               | Belgium |
+----------------+------------------------------------------+---------+
| Hein J. W. de  | Netherland Institute for Sea Research    | Neth    |
| Baar           |                                          | erlands |
+----------------+------------------------------------------+---------+
| Richard A.     | Pacific Marine Environmental Laboratory, | USA     |
| Feely          |                                          |         |
|                | National Oceanographic and Atmospheric   |         |
|                | Administration                           |         |
+----------------+------------------------------------------+---------+
| Gernot         | Monterey Bay Aquarium Research Institute | USA     |
| Friederich     |                                          |         |
+----------------+------------------------------------------+---------+
| John           | Lamont-Doherty Earth Observatory,        | USA     |
| Goddard^\*\*^  | Columbia University                      |         |
+----------------+------------------------------------------+---------+
| Burke Hales    | College of Oceanic and Atmospheric       | USA     |
|                | Sciences,                                |         |
|                |                                          |         |
|                | Oregon State University                  |         |
+----------------+------------------------------------------+---------+
| Mario Hoppema  | Alfred Wegener Institute for Polar and   | Germany |
|                | Marine Research                          |         |
+----------------+------------------------------------------+---------+
| Masao Ishii    | Meteorological Research Institute        | Japan   |
+----------------+------------------------------------------+---------+
| Truls          | Bjerknes Centre for Climate Research,    | Norway  |
| Johannessen    | University of Bergen                     |         |
+----------------+------------------------------------------+---------+
| Nicolas Metzl  | Laboratoire d'Oceanographie et du        | France  |
|                | Climat,                                  |         |
|                |                                          |         |
|                | Universite Pierre et Marie Curie         |         |
+----------------+------------------------------------------+---------+
| Takashi        | Meteorological Research Institute        | Japan   |
| Midorikawa     |                                          |         |
+----------------+------------------------------------------+---------+
| Timothy        | Lamont-Doherty Earth Observatory,        | USA     |
| Newberger      | Columbia University                      |         |
+----------------+------------------------------------------+---------+
| Yukihiro       | National Institute for Environmental     | Japan   |
| Nojiri         | Studies                                  |         |
+----------------+------------------------------------------+---------+
| Jon Olafsson   | Marine Research Institute and University | Iceland |
|                | of Iceland                               |         |
+----------------+------------------------------------------+---------+
| Are Olsen      | Bjerknes Centre for Climate Research,    | Norway  |
|                | University of Bergen                     |         |
+----------------+------------------------------------------+---------+
| Christopher L. | Pacific Marine Environmental Laboratory, | USA     |
| Sabine         |                                          |         |
|                | National Oceanographic and Atmospheric   |         |
|                | Administration                           |         |
+----------------+------------------------------------------+---------+
| Ute Schuster   | School of Environmental Sciences,        | UK      |
|                | University of East Anglia, Norwich       |         |
+----------------+------------------------------------------+---------+
| Stewart C.     | Lamont-Doherty Earth Observatory,        | USA     |
| Sutherland     | Columbia University                      |         |
+----------------+------------------------------------------+---------+
| Colm Sweeney   | Earth System Research Laboratory,        | USA     |
|                | National Oceanographic and Atmospheric   |         |
|                | Administration                           |         |
+----------------+------------------------------------------+---------+
| Taro Takahashi | Lamont-Doherty Earth Observatory,        | USA     |
|                | Columbia University                      |         |
+----------------+------------------------------------------+---------+
| Bronte         | Australian Commonwealth Scientific and   | Au      |
| Tilbrook       | Research Organization (CSIRO) Marine and | stralia |
|                | Atmospheric Research                     |         |
+----------------+------------------------------------------+---------+
| Rik Wanninkhof | Atlantic Oceanographic and               | USA     |
|                | Meteorological Laboratory, National      |         |
|                | Oceanographic and Atmospheric            |         |
|                | Administration                           |         |
+----------------+------------------------------------------+---------+
| Andrew Watson  | School of Environmental Sciences,        | UK      |
|                | University of East Anglia                |         |
+----------------+------------------------------------------+---------+
| Ray F. Weiss   | Scripps Institution of Oceanography,     | USA     |
|                | University of California San Diego       |         |
+----------------+------------------------------------------+---------+
| C. S. Wong     | Institute of Ocean Sciences              | Canada  |
+----------------+------------------------------------------+---------+
| H.             | Graduate School of Environmental Earth   | Japan   |
| Y              | Science,                                 |         |
| oshikawa-Inoue |                                          |         |
|                | Hokkaido University                      |         |
+----------------+------------------------------------------+---------+

^\*^The PI names are given in the alphabetical order.

^\*\*^Retired

**6. DATA LISTING**

This NDP consists of two files: the file called "LDEO_database.txt"
contains all the numerical data, and the file "heading.txt" contains
information on the data source, credit, institution, etc. The data
elements in "LDEO_Database.txt" and their units are listed in Table 2;
and those in "Metadata.xls" are explained in Table 3. Detailed cruise
documentation (such as names of ship and ports and dates for departure
and arrival) may be obtained directly from the respective PI's.

**Table 2. Data elements listed in the master data file
"LDEO_Database.txt"**

+----------------+-----------------------------------------------------+
| FILENAME^\*^   | Internal LDEO File Name                             |
+----------------+-----------------------------------------------------+
| STN^\*^        | Station number assigned in the LDEO File            |
+----------------+-----------------------------------------------------+
| LAT            | Latitude in decimal degrees (North is positive)     |
+----------------+-----------------------------------------------------+
| LON            | Longitude in decimal degrees (East is positive)     |
+----------------+-----------------------------------------------------+
| MONTH/DAY/YEAR | Date                                                |
+----------------+-----------------------------------------------------+
| JDATE          | Julian Date in decimal notation. Convention is 0001 |
|                | UTC 1 Jan = 1.0                                     |
+----------------+-----------------------------------------------------+
| VCO2_SW^\*\*^  | Mole fraction concentration of CO~2~ (ppm) in dried |
|                | air                                                 |
+----------------+-----------------------------------------------------+
| PCO2_TEQ       | Partial Pressure of CO~2~ in seawater               |
|                | (microatmospheres) at the temperature in the        |
|                | TEMP_PCO2 column                                    |
+----------------+-----------------------------------------------------+
| TEMP_PCO2      | Temperature at which pCO~2~ was measured in ºC      |
+----------------+-----------------------------------------------------+
| SST            | Sea Surface Temperature in ºC                       |
+----------------+-----------------------------------------------------+
| SSS            | Sea Surface Salinity                                |
+----------------+-----------------------------------------------------+
| PCO2_SST       | Partial Pressure of CO~2~ in seawater (in units of  |
|                | microatmospheres) at                                |
|                |                                                     |
|                | the temperature in the SST column                   |
+----------------+-----------------------------------------------------+
| PCO2_TEQ       | Partial Pressure of CO~2~ in seawater (in units of  |
|                | microatmospheres) at the temperature in             |
|                | theTEMP_PCO2 column. This is ordinarily the value   |
|                | that is actually measured                           |
+----------------+-----------------------------------------------------+
| EQ_PBARO       | Pressure in the equilibration vessel in units of    |
|                | millibars                                           |
+----------------+-----------------------------------------------------+
| SHIPPBARO      | Barometric pressure in the outside air from the     |
|                | ship's observation system in units of millibars     |
+----------------+-----------------------------------------------------+

^\*^Cross reference fields to the internal LDEO file name in case
problems are discovered

^\*\*^Missing data have the value -999.9

**Table 3. Data elements listed in the metadata file "Metadata.xls"**

  ------------- ---------------------------------------------------------
  FILENAME      Internal LDEO File Name

  DIRNAME       Directory Name for the Internal LDEO File Name

  LEG           Leg Number. This is an arbitrary designation in many
                files because of our limit of four characters for a
                station number. For surface underway files that normally
                have many more than 9,999 observations we have broken the
                file into "legs."

  SHIP          The name of the ship or other platform used

  OBSERVER      A notation of the person making the observation or
                responsible for running the collection system

  DEPARTPORT    Port of Departure

  DEPARTDATE    Date of Departure

  ARRIVEPORT    Port of Arrival

  ARRIVEDATE    Date of Arrival

  CRUISENAME    A notation to identify the general name of the cruise

  COMMENT^\*^   Air data source and general information
  ------------- ---------------------------------------------------------

^\*^Additional information may be available for a particular file if
needed.

**7. HOW TO OBTAIN THE DATA AND DOCUMENTATION**

The LDEO database (NDP-088) is available free of charge from CDIAC. The
complete documentation and data can be obtained from the CDIAC
oceanographic web site (http://cdiac.ornl.gov/oceans/doc.html), through
CDIAC's online ordering system
(http://cdiac.ornl.gov/pns/how_order.html) or by contacting CDIAC.

The data are also available from CDIAC's anonymous file transfer
protocol (FTP) area via the Internet. (Please note that your computer
needs to have FTP software loaded on it; this software is included in
most new operating systems.) Use the following commands to obtain the
database:

ftp cdiac.ornl.gov or \>ftp 160.91.18.18

Login: "anonymous" or "ftp"

Password: your e-mail address

ftp\> cd pub/ndp088/

ftp\> dir

ftp\> mget (files)

ftp\> quit

Contact information:

Carbon Dioxide Information Analysis Center

Oak Ridge National Laboratory

P.O. Box 2008

Oak Ridge, Tennessee 37831-6335

USA

Telephone: (865) 574-3645

Telefax: (865) 574-2232

E-mail: cdiac@ornl.gov

Internet: <http://cdiac.ornl.gov/>

**8. ACKNOWLEDGEMENTS**

Many national and international investigators contributed their
observations to this database. ORNL gratefully acknowledges the efforts
of investigators and supporting staff at sea and on land. Richard A.
Feely \[Pacific Marine Environmental Laboratory/National Oceanographic
and Atmospheric Administration (PMEL/NOAA)\] and Rik Wanninkhof
\[Atlantic Oceanographic and Meteorological Laboratory (AOML) /NOAA\]
offered encouragement in this task; this was appreciated. . We
gratefully acknowledge that the continued support from the Office of
Global Programs of the National Oceanic and Atmospheric Administration
has made this compilation possible. The field study of T. Takahashi and
his associates have been supported by the National Science Foundation
and Department of Energy.

# 9. REFERENCES

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changes, 1993--2002: Implications for the partitioning of fossil fuel
CO~2~ sequestration," *Global Biogeochemical Cycles* 19:GB4017,
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Broecker, W.S. and T. Takahashi. 1966. „Calcium carbonate precipitation
on the Bahama Banks," *Journal of Geophysical Research* 71:1575--1602.

Chavez, F. and T. Takahashi. 2007. Coastal oceans, Chapter 15, in "The
First State of the Carbon Cycle Report (SOCCR): North American Carbon
Budget and Implications for the Global Carbon Cycle". A report by the
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air-sea flux," *Journal of Geophysical Research* 106(C12):31155--66.

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Sarmiento, J. L., P. Monfray, E. Maier-Reimer, O. Aumont, R.J. Murnane,
and J.C. Orr. 2000. "Sea-air CO~2~ fluxes and carbon transport: A
comparison of three ocean general circulation models." *Global
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Takahashi, T. 1961. "Carbon dioxide in the atmosphere and in the
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Takahashi, T., J. Olafsson, J. Goddard, D.W. Chipman, and S.C.
Sutherland. 1993. "Seasonal variation of CO~2~ and nutrients in the
high-latitude surface oceans: A comparative study," *Global
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Takahashi, T., R.A. Feely, R. Weiss, R. Wanninkhof, D.W. Chipman, S.C.
Sutherland, and T. Takahashi. 1997. "Global air-sea flux of CO~2~: an
estimate based on measurements of sea-air pCO~2~ difference," *Proc.
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Takahashi, T., S.C. Sutherland, C. Sweeney, A. Poisson, N. Metzl, B.
Tillbrook, N. Bates, R. Wanninkhof, R.A. Feely, C.L. Sabine, J.
Olafsson, and Y. Nojiri. 2002. "Global sea-air CO~2~ flux based on
climatological surface ocean pCO~2~, and seasonal biological and
temperature effects," *Deep-Sea Research II*, 49:1601--22.

Takahashi, T. S.C. Sutherland, R. Wanninkhof, C. Sweeney, R.A. Feely,
C.L. Sabine, B. Hales, G. Friederich, F. Chavez, A. Watson, D.C.E.
Bakker, N. Mezl, H. Yoshikawa-Inoue, T. Midorikawa, M. Ishii, M.
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TRENDS on line. 2006. "A Compendium of Data on Global Change. Carbon
Dioxide Information and Analysis Center," Oak Ridge National Laboratory,
U.S. Department of Energy, Oak Ridge, TN
http://cdiac.ornl.gov/trends/co2/contents/html)