Columbus Waikato/Cap Victor Master Readme File

As CO~2~ concentrations increase in the atmosphere due largely to fossil
fuel combustion and deforestation, it becomes increasingly important to
understand the fate of this gas as it leaves the atmosphere. By
measuring the partial pressure of CO~2~ (pCO~2~) in both the sea surface
and atmosphere, the flux of CO~2~ either into or out of the ocean can be
calculated, affording a broader understanding of the distribution of
CO~2~ in the surface ocean.

In 2004, PMEL installed an underway pCO~2~ system on the container ship
Columbus Waikato to monitor atmospheric and surface water CO~2~
concentrations as the ship traversed the Pacific Ocean from the western
united states to New Zealand. In the time period between Feb 2004 and
Feb 2006 we collected 13 data sets along this ship track.

![](media/image1.jpeg){width="4.302777777777778in"
height="2.5166666666666666in"}

In March, 2006, the ship changed it's route to as well as it's name. The
ship is now the Cap Victor, and the new ship track is shown below.

![](media/image2.jpeg){width="4.302777777777778in"
height="2.5166666666666666in"}

PMEL continues to measure pCO~2~ while the Cap Victor is transiting the
Pacific Ocean.

# Analysis Method

The Underway pCO~2~ system utilizes a Licor 6262 Infrared Analyzer (IR)
to determine the mole fraction of CO~2~ in the air and surface seawater.
Seawater from an intake in the bow is continuously supplied to a
plexiglas equilibrator consisting of a \~0.5 L water reservoir and \~0.8
L gaseous headspace. The water is showered into the equilibrator at a
rate of approximately 2 liters/minute, and the headspace gas is
circulated at a rate of 60 to 80 ml/minute. As the water flows through
the equilibrator chamber, the dissolved CO~2~ gas partitions between the
water and the headspace. This air is subsequently sampled by the Licor
analyzer to determine the mole fraction of CO~2~ in the seawater. In the
Licor, infrared radiation is passed through two gas sampling cells to
detect the CO~2~ absorption of the gases in the cells. The reference
cell is continuously supplied with dried air scrubbed of CO~2~, and the
sample cell is supplied with the gas being measured. The IR outputs a
reading proportional to the difference between the CO~2~ absorption
detected in the two cells. Because it is necessary for the gases in the
reference and sample cells of the Licor analyzer to be at the same
pressure, the flow of gas is halted for several seconds before the IR
readings are saved so that both cells will be at ambient pressure.

Atmospheric air is also continuously supplied to the pCO~2~
instrumentation by a 3/8" Decaron aluminum-lined tube that runs from the
engine room, through several decks, then along the port side of the ship
to the bow. Both the atmospheric air and the equilibrator air pass
through naphion tubing and silica gel to condense and trap moisture.

![](media/image3.jpeg){width="4.555555555555555in"
height="3.4166666666666665in"}

In addition to CO~2~ values, the system collects the following data:

Surface seawater temperature at the seawater intake

Seawater temperature from the equilibrator

Conductivity and salinity from a Seabird TSG mounted next to the pCO~2~
system

Barometric pressure in the Licor, and in the equilibrator

Latitude and longitude from a GPS mounted near the bridge

Sea surface temperature, salinity, and barometric pressure are necessary
to calculate partial pressure of CO~2~ (pCO~2~) or fugacity (fCO~2~)
from the mole fraction values that are measured at the Licor IR.
Equilibrator temperatures are used to correct for warming that occurs in
the sea water as it travels from the bow intake to the wet lab since
pCO2 is temperature dependant. Calculations of pCO~2~ and fCO~2~ are
detailed in the Department of Energy handbook of methods for the
analysis of the various parameters of the carbon dioxide system in sea
water; version 2.

The underway pCO~2~ system completes a full cycle of measurements every
112 minutes. The cycle starts with 4 standard gases traceable to the WMO
scale, then measures 10 atmospheric samples, followed by 60 surface
water samples. Each new gas is flushed through the Licor Analyzer for 4
minutes prior to a 10 second reading from the analyzer during which the
sample cell is open to the atmosphere. Subsequent samples of the same
gas are flushed through the Licor Analyzer for 30 seconds prior to a
stop-flow measurement.

# 

# File Format

**COLUMN HEADER DESCRIPTION**

1\. Group/Ship: PMEL/Waikato or PMEL/CapVictor

2\. Cruise_ID: CW\<Year\>\_\<Month\> or CV\<Year\>\_\<Month\>

3\. JD_GMT: Decimal year day

4\. Date_MM/DD/YY: Date in the format mm/dd/yy

5\. Date_DDMMYYYY Date in the format DDMMYYYY

6\. Time: GMT HH:MM:SS

7\. Latitude: Latitude in decimal degrees (negative values are in

> southern hemisphere).

8\. Longitude: Longitude in decimal degrees (negative values are

> in western latitudes).

9\. xCO2eq_ppm: Mole fraction of CO2 (dry) in the headspace

> equilibrator at equilibrator temperature (Teq) in
>
> parts per million. Water comes from bow intake 2m below the water
> line.

10\. xCO2atm_ppm: Mole fraction of CO2 in air in parts per million.

11\. xCO2_atm_ave_ppm: xCO2atm_ppm averaged linearly to match up with

> measurements xCO2eq_ppm

12\. Press_Equ_mbar: Barometric pressure in the equilibrator

13\. Teq\_°C: Temperature in the equilibrator water.

14\. SST\_°C: Temperature from the ship\'s bow intake.

15\. Salinty: Thermosalinograph salinity

16\. H2O_flow_l/min: Water flow through equilibrator in liters/minute.

17\. IR_gas_flow_ml/min: Gas flow through the Licor infrared analyzer

before the flow is stopped in ml/minute.

18\. Temp_IR\_°C Temperature of the Licor sample cell in °C

19\. fCO2sw \_uatm: Fugacity of CO2 in sea water in

> microatmospheres calculated as outlined in the DOE Handbook.

20\. fCO2a_uatm: Fugacity of CO2 in air in microatmospheres

21\. dfCO2_uatm: Sea water fCO2 - air fCO2 in microatmospheres.

22\. QC Flag Quality control flag 2 = Good value

3 = Questionable value

4 = Bad value

23\. Sub Flag Descriptive quality control flag used when a value

> receives a "3" QC flag
>
> 1 = Standard out of range
>
> 2 = Questionable SST
>
> 3 = Questionable EqT
>
> 4 = Anomalous ΔT (EqT -- SST)
>
> 5 = Excess of warming of the seawater
>
> 6 = Questionable salinity
>
> 7 = Questionable pressure
>
> 8 = Low equilibrator gas flow
>
> 9 = Questionable air value
>
> 10 = Interpolated standard value
>
> 11 = Other, see metadata

# Collaborative Partners

Ms. Carolyn Wolfe, Southern California Marine Institute
(http://www.scmi.us)

Dr. Paul Quay, University of Washington, School of Oceanography
(http://www.ocean.washington.edu)

Dr. Bronte Tilbrook, CSIRO Marine and Atmospheric Research
(http://www.cmar.csiro.au/research/co2.html)

# References 

DOE (1994). Handbook of methods for the analysis of the various
parameters of the carbon

dioxide system in sea water; version 2. A.G. Dickson and C. Goyet, eds.,
ORNL/CDIAC-74.

Feely, R.A., R. Wanninkhof, H.B. Milburn, C.E. Cosca, M. Stapp, and P.P.
Murphy, A new automated underway system for making high precision pCO~2~
measurements onboard research ships, Analytica Chim. Acta, 377, 185-191,
1998.

Wanninkhof, R. and K. Thoning (1993) Measurement of fugacity of CO~2~ in
surface water using

continuous and discrete sampling methods. Mar. Chem. 44(2-4): 189-205.

Weiss, R. F. (1970) The solubility of nitrogen, oxygen and argon in
water and seawater.

Deep-Sea Research 17: 721-735.

Weiss, R. F. (1974) Carbon dioxide in water and seawater: the solubility
of a non-ideal gas.

Mar. Chem. 2: 203-215.

Weiss, R. F., R. A. Jahnke and C. D. Keeling (1982) Seasonal effects of
temperature and

salinity on the partial pressure of CO~2~ in seawater. Nature 300:
511-513.