R/V SONNE cruise:		SO235
Expocode:			06BE20140723

Initial submission:		2016
Most recent update:		12. Jan 2016

Date of cruise (dd/mm/yyyy):	23.07. - 08.08.2014
Geographic coverage: 		20S, 55E - 5N, 74W
Ports of call: 			Port Louis, Mauritius - Male, Maldives

Vessel name:	R/V Sonne
Vessel ID:	DFCG
Country:	Germany

PI:		Tobias Steinhoff
		GEOMAR Helmholtz Centre for Ocean Research Kiel
		Duesternbrooker Weg 20
		24105 Kiel
		Germany
		tsteinhoff@geomar.de

Reported  variables:
(1-3)	Year|Month|Day		date
(4-6)	Hour|Minute|Second		time (UTC)
(7)	Day of year			decimal year day
(8)	Longitude [deg E]		Longitude in decimal degrees E
(9)	Latitude [deg N]		Latitude in decimal degrees N
(10)	SST [deg C]			Sea surface temperature in deg C
(11)	SSS				Sea surface salinity 
(12) 	Atm. Pressure [mbar]		Atmospheric pressure in mbar
(13)	Equi Temp [deg C]		Water temperature inside the equilibrator in deg C
(14)	Equi Press [mbar]		Pressure inside the equilibrator in mbar
(15)	xCO2 (equi temp, dry) [ppm]	mole fraction of CO2 in the equilibrator 
      headspace (dry) at equilibrator  temperature in ppm	
(16)	pCO2 (SST, 100hum) [uatm]	partial pressure of CO2 in seawater at SST and
      100% humidity in atm
(17)	fCO2 (SST, 100hum) [uatm]	fugacity of CO2 in seawater at SST and
      100% humidity in atm
(18)	Atm. xCO2 (dry) [ppm]		mole fraction of CO2 of atmospheric air in ppm
(19)	Atm xCO2 (dry, running mean) [ppm]	same as 18 but with a running mean (500 minutes) to 
						interpolate between measurements.

Instrument information:
- SST (+/- 0.05 deg C):
SST was measured with a thermosalinograph from Seabird (SBE37) which was installed in the ships moon pool next to the inlet pump at approximately 6 m depth.

-Equilibrator temp (+/-0.05 deg C):
Due to a broken temperature probe, we used the temperature of an Aanderaa Optode that was placed in a continuously flushed water bath next to the equilibrator. We still estimate the accuracy of the equilibrator to 0.05 deg C.

-SSS (+/- 0.1):
SSS was measured with a thermosalinograph from Seabird (SBE37) which was installed in the ships moon pool next to the inlet pump at approximately 6 m depth.

-Atmospheric press. (+/- 0.1 mbar):
The atmospheric pressure was measured by the ships weather station.

-Equilibrator press (+/- 0.1 mbar):
The equilibrator is open to the atmosphere. Here we assume to have atmospheric pressure in the equilibration chamber.

-pCO2/fCO2 (+/- 2uatm):	
	IR sensor:		Licor 6252, calibrated with 3 standard gases.
	Standard gases:		Deuste Steininger (208.96 402 602.4), 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 Weiss equilibrator was used for the equilibration. The sample gas stream was first dried by cooling and then with a Nafion dryer.
The gas was first led to the LI-6252 for the pCO2 measurements and then through a LGR N2O analyzer. The system is described in detail in Arevalo et al. (2012) 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). 
The atmospheric xCO2 values are very noisy and are reported as is. 

References:
Arevalo-Martinez, D.L.,  M. Beyer, M. Krumbholz, I. Piller, A. Kock, T. Steinhoff, A. Koertzinger, and H. W. Bange (2013). A new method for continuous measurements of oceanic and atmospheric N2O, CO and CO2: performance of off-axis integrated cavity output spectroscopy (OA-ICOS) coupled to non-dispersive infrared detection (NDIR). Ocean Sci., 9, 1071-1087, doi:10.5194/os-9-1071-2013.

Pierrot, D., Neill, C., Sullivan, K., Castle, R., Wanninkhof, R., Leger, 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








