DOI: 10.1594/pangaea.883799
title: CFC, and noble gas measurements during POLARSTERN cruise PS82 (ANT-XXIX/9)

description: The tracer data set was carefully checked for accurate measurements and outliers. According to the WOCE standards the following flags were applied to each measurement: ? = flag 3 = doubtful; / = flag 4 = bad, # = flag 6 = mean of replicates.Noble gases (3He, 4He, 20Ne): We took 540 water samples for stable noble gas isotopes (3He, 4He, Ne) in copper tubes from 68 stations. In the IUP Bremen noble gas lab the samples were processed in a first step with a UHV (ultra high vacuum) gas extraction system. The required vacuum conditions are achieved by a rotary pump and an oil diffusion pump. To maintain contamination-free samples, the extraction system is checked for leaks on each sample separately. Sample gases are transferred via water vapour into a glass ampoule kept at liquid nitrogen temperature. Quality checks of this sample preparation line are done on a routine basis. This includes special vacuum checks and preparing accurately defined samples for internal control measurement. For analysis of the noble gas isotopes the glass ampoules are connected to a fully automated UHV mass spectrometric system equipped with a two stage cryo system. Every 2 to 4 samples the system is calibrated with atmospheric air standards (reproducibility &lt;0.2%). Also measurement of line blanks and linearity are done. The performance of the Bremen facility is described in Sültenfuß et al. (2009, doi:10.1080/10256010902871929). Error estimate for absolute He and Ne concentrations and the d3He: D(4He) &lt; 1.0 %D(Ne) &lt; 1.0 %D(d3He) &lt; 0.5 % Chlorofluorocarbons (CFC-11, CFC-12): For the transient tracers (chlorofluorocarbons, CFC-11, CFC-12), we took 1080 samples on 94 stations. The Chlorofluorocarbon (CFC-11 and CFC-12) water samples from the CTD-bottle-system are stored in glass ampoules without contact to the atmosphere during the taping. Immediately after sampling the ampoules are flame sealed after a CFC free headspace of pure nitrogen had been applied. The loss of CFCs into the headspace is considered by a careful equilibration between liquid and gas phase under controlled conditions before the sealed ampoules are opened and a precise measurement of the volume of the headspace. The determination of CFC concentrations in the IUP Bremen gas chromatography lab is accomplished by purge and trap sample pre-treatment followed by gas chromatographic (GC) separation on a capillary column and electron capture detection (ECD). The system is calibrated by analyzing several different volumes of a known standard gas. CFC concentrations are calibrated on SIO98 scale (Prinn et al., 2000, doi:10.1029/2000JD900141). A more detailed description of the measurement system is given by Bulsiewicz et at. (1998, doi:10.1029/98JC00140). Concentrations of CFC-11 and CFC-12 reported on SIO 98 scale (Prinn et al., 2000, doi:10.1029/2000JD900141). Overall accuracy, including that off the calibration scale is estimated to be 2.5% for CFC-11 and 1.5% for CFC-12. The accuracy accounts for uncertainties of calibrated sample volume, calibration curve, extraction efficiency, standard and working gas, water blank, etc. Acknowledgment: Sampling on board and measurement of CFCs and noble gases at the IUP Bremen was funded by the Deutsche Forschungsgemeinschaft within the SPP 1158 "Antarktisforschung", grant HU 1544/4-1. We thank Rainer Knust and the scientific party to participate in the ANT XXIX/9 expedition and for the excellent assistance and cooperation on board. We thank also master and crew of RV Polarstern.