CO2_readme.txt
University of New Hampshire Coastal Ocean Observing Center

Underway Carbon Dioxide Data description

Investigators: Doug Vandemark, Joe Salisbury, Ru Morrison, Jeffrey Runge, Janet Campbell, Chris Hunt, Wade McGillis

Contact: Doug Vandemark (doug.vandemark@unh.edu)

PLEASE NOTE: Users of data will be required to provide proper credit and acknowledgment of the provider.  Users of data are encouraged to discuss relevant findings with the provider early in the research.  The user is required to give all providers of the data being used a copy of any manuscript resulting from use of the data prior to the initial submission for publication, thus giving the data provider an opportunity to comment on the paper. The provider(s) shall have the right to be named as a co-author.

CO2 Analyzer: Licor 6262 or Licor 840 infrared (IR) analyzer (Li-cor Biosciences Inc, Lincoln NE).

Drying method:  Nafion selectively permeable membrane drying loop (Perma Pure, Toms River NJ) with counter-flowing nitrogen stream.

Equilibrator type:  Three-chamber fast-rate equilibrator similar to that of Wanninkhof and Thoning (1993, reference below), flow rate 1.5 l/min.

CO2 calibration standards:  Two-point calibration using ultrapure nitrogen and a mixture of CO2 in nitrogen, ranging from 832.3 to 856.1 ppm.  Mixtures of CO2 in nitrogen, analyzed to within +/- 1%, were obtained from Scott-Marrin Inc (Riverside, CA).  These standards are then adjusted based on comparison to a series of standards ranging from 378-515 ppmv obtained from NOAA/ESRL (http://www.esrl.noaa.gov/).

Seawater temperature and salinity were measured using a SBE 45 thermosalinograph, pumped at 1.5 l/min.  Tests using a handheld temperature and salinity sensor (YSI 85, YSI Instruments Yellow Springs OH), aboard the RV Gulf Challenger indicate temperature differences are less than 0.01 degree Celcius between equilibrator outflow and intake sea surface water.  Therefore, no temperature correction is applied to data taken aboard the RV Gulf Challenger.  A temperature correction of 0.15 degrees Celcius is applied to data taken aboard the RV Oceanus (cruises from 10/31/2006 to 11/11/2006).

CO2 data calculation: Corrections of the data for water vapor pressure and sea surface temperature and conversion from pCO2 to the fugacity of carbon dioxide (fCO2) were carried out according to the DOE handbook (1994).
 
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.

Wanninkhof, R. and Thoning, K.  1993.  Measurement of fugacity of CO2 in surface water using continuous and discrete sampling methods.  Marine Chemistry 44: 189-204.