 |
|
Home > Data Description > CFC and SF6 Data
John Bullister and David Wisegarver
NOAA-PMEL
7600 Sand Point Way NE
Seattle, WA 98115
206-526-6741
John.L.Bullister@noaa.gov
David Wisegarver@noaa.gov
The HOT site is located at 22.75oN, 158oW in the North Pacific subtropical gyre. Vertical profiles of dissolved CFC11 and CFC12 were collected at the HOT site in May 2005 (HOT 169). Vertical profiles of dissolved CFC11, CFC12 and SF6 were collected at the HOT site in Oct. 2005 (HOT 174). Seawater samples were collected in 10 liter PVC sample bottles, and aliquots for CFCs and SF6 analysis were immediately transferred into 200 cc glass syringes to minimize contact with air. About 150 cc of water from a syringe was transferred to a purge and trap system and analyzed for CFC11, CFC12 and SF6 on board ship based on methods described by Vollmer and Weiss [2002].
CFC values are reported based on the SIO98 calibration scale [Prinn et al. 2000]. SF6 values are reported on the GMD2000 scale ([http://www.cmdl.noaa.gov/hats) CFC concentrations are given in units of picomoles per kilogram seawater (pmol kg-1) where 1 pmol = 10-12 mole SF6 concentrations are given in units of femtomoles per kilogram seawater (fmol kg-1 ) where 1 fmol = 0.001 pmol)
The estimated precision of the dissolved CFC measurements is ~1% or 0.005 pmol kg-1, whichever is greater. Overall accuracy of the measurements (including errors in calibration scales) for the CFCs is estimated to be ~2% or 0.010 pmol kg-1, whichever is greater. Blank levels (based on analysis of abyssal samples at HOT thought to be tracer free) for the CFCs were ~0.003 pmol kg-1. The precision of the dissolved SF6 measurements was ~ 2% or 0.02 fmol kg-1, whichever was greater, with an estimated overall accuracy of ~ 4% or ~0.04 fmol kg-1, whichever was greater. Blank levels for SF6 are estimated as ~0.01 fmol kg-1. No blank corrections have been applied to the data reported.
Bullister, J.L., D.P. Wisegarver and R.E. Sonnerup, 2006. Sulfur Hexafluoride as a Transient Tracer in the North Pacific Ocean. Geophys. Res. Lett., vol 33, doi: 10.1029/2006GL026514, 2006
Prinn, R. G., et al. (2000), A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE J. Geophys. Res., 105, 17,751-17,792, 2000.
Vollmer, M. K. and R. F. Weiss (2002), Simultaneous determination of sulfur hexafluoride and three chlorofluorocarbons in water and air. Mar. Chem., 78, 137-148.
Download CFC & SF6 data (via FTP)