M/V Atlantic  Companion cruise:		COM_36

This cruise were part of the European CARBOOCEAN project.

Initial submission:		2008
Most recent update:		20. Dec 2010

Date of cruise (dd/mm/yyyy):	13.10. - 18.10.2007
Geographic coverage: 		52N, 7W - 44N, 63W
Ports of call: 			Halifax, Canada - Liverpool, UK

Vessel name:	M/V Atlantic Companion
Vessel ID:	SKPE
Country:	Sweden
Owner:		Atlantic Container Lines

PI:		Tobias Steinhoff
		Leibniz Institute of Marine Sciences (IFM-GEOMAR)
		Duesternbrooker Weg 20
		24105 Kiel
		Germany
		tsteinhoff@ifm-geomar.de

Citation: 	Steinhoff, T., Wallace, D.W.R. and Koertzinger, A. (2007). 
		Underway fCO2 measurements in the North Atlantic Ocean on 
      M/V Atlantic Companion in October 2007.

Reported  variables:
(1)	Cruise ID
(2-4)	Year|Month|Day		date
(5-7)	Hour|Minute|Second		time (UTC)
(8)	Day of year			decimal year day
(9)	Longitude [deg E]		Longitude in decimal degrees E
(10)	Latitude [deg N]		Latitude in decimal degrees N
(11)	SST [deg C]			Sea surface temperature in deg C
(12)	SSS				Sea surface salinity 
(13) 	Atm. Pressure [mbar]		Atmospheric pressure in mbar
(14)	Equi Temp [deg C]		Water temperature inside the equilibrator in deg C
(15)	Equi Press [mbar]		Pressureinside the equilibrator in mbar
(16)	xCO2 (equi temp, dry) [ppm]	mole fraction of CO2 in the equilibrator 
      headspace (dry) at equilibrator  temperature in ppm	
(17)	pCO2 (SST, 100hum) [uatm]	partial pressure of CO2 in seawater at SST and
      100% humidity in uatm
(18)	fCO2 (SST, 100hum) [uatm]	fugacity of CO2 in seawater at SST and
      100% humidity in uatm
(19)	Atm. xCO2 (dry) [ppm]		mole fraction of CO2 of atmospheric air in ppm
(20)	Atm xCO2 (dry, running mean) [ppm]	same as 18 but with a running mean to interpolate 
						between measurements.


Instrument information:
- SST (+- 0.05 deg C):
SST was measured with a thermosalinograph from Seabird (SBE21) with an external SBE38 which was installed approximately 30 cm after the seawater intake. Both instruments were calibrated approximately every 6 months.

-SSS (+- 0.1 PSU):
SSS was measured with a thermosalinograph from Seabird (SBE21) which was calibrated approximately every 6 months.

-Atmospheric press. (+- 0.1 mbar):
The atm. Pressure was measured on the top of the vessel, using a static pressure head to minimize wind induced errors.

-Equilibrator temp (0.05 C):
The temperature probe inside the equilibrator was compared to the SBE38 every 3 months.

-Equilibrator press (+- 0.1 mbar):
Differential measurement. For the pressure outside the equilibrator atmospheric pressure was used and 3 mbar were added to account for the height difference and possible overpressure inside the engine room: Pequ = Patm + 3mbar + Pequ(differential)

-pCO2/fCO2 (+- 3uatm):	
	IR sensor:		Licor 7000, calibrated with 3 standard gases.
	Standard gases:		Deuste Steininger (249.3, 350.1, 450.2 ppm), calibrated against 
      NOAA/CMDL standard gases. Resulting uncertainty: +- 0.5 ppm.
	Water flow rate: 	2-3 L min-1
	Gas flow rate:		100 mL min-1

A so-called Neill system was used for pCO2 measurements. The system is described in detail in Pierrot (2009) and the whole setup is described in Steinhoff (2010). Surface water is pumped continuously (by a torque flow pump) from the intake to the equilibrator. The equilibrator contains a water spray head, and as the water flows through it the dissolved CO2 equilibrates with the headspace. The headspace is dried and xCO2 is determined by an infrared sensor. Calculations were performed following Pierrot (2009) and are described in detail in Steinhoff (2010). 


References:
Pierrot, D., Neill, C., Sullivan, K., Castle, R., Wanninkhof, R., Luger, H., Johannessen, T.,
Olsen, A., Feely, R. A., and Cosca, C. E. (2009). Recommendations for autonomous underway
pCO2 measuring systems and data reduction routines. Deep-Sea Res. II , 56, 512_522.

Steinhoff, T. (2010). Carbon and nutrient fluxes in the North Atlantic Ocean. Dissertation. http://eldiss.uni-kiel.de/macau/receive/dissertation_diss_00005704