Chlorofluorocarbons and noble gas measured on water bottle samples during POLARSTERN cruise ANT-XXV/4

DOI

On the two Drake Passage sections we took a total of 250 samples for helium isotopes and neon, distributed on 26 profiles down to the bottom (14 on the eastern section and 12 on the section along the Shackleton Ridge), mainly to capture the SPDSW core. Additionally we took one profile in a volcano near King George Island.The helium isotope and neon water samples are tapped in copper tubes, carefully preventing contamination with air during the filling. The tubes are squeezed at both ends to keep them gas tight during transportation and storage. They are shipped home immediately after the cruise. In our Bremen nobler gas lab the gases were extracted from the samples and then analysed with a sector field and quadrupole mass spectrometer.In total we took 580 samples for CFCs distributed on 40 deep profiles (23 on the eastern section and 17 on the section along the Shackleton Ridge)on the two Drake Passage sections to investigate the transit times and pathways of various deep water masses. Furthermore, we sampled for one profile inside and one profile close to the volcano near King George Island in Brainsfield Strait.The CFC water samples are stored in glass ampoules without contact to the atmosphere during tapping. Immediately after sampling the ampoules are flame sealed after a CFC free headspace of pure nitrogen had been applied. Also the CFC samples are shipped home for analysis in our Bremen gas chromatography lab. The measurements are performed by purging the water sample with nitrogen and trapping the gases on a cooling trap. Subsequently the amount of CFC-11 and CFC-12 are determined with a gas chromatograph and electron capture detector system (GC/ECD).The water samples for helium isotopes and neon from the CTD-bottle-system are tapped in copper tubes, preventing air contamination and bubbles during the filling of the tubes and squeezed at both ends to keep them gas tight during transportation and storage.In the IUP Bremen noble gas lab the samples are 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 <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 noble gases concentrations:D(4He) < 1.0 %D(Ne) < 1.0 %D(d3He) < 0.5 %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 tapping. 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:10.1029/98JC00140). A more detailed description of the measurement system is given by Bulsiewicz et at. (1998, doi:10.1029/2000JD900141).Accuracy (i.e. uncertainties of calibrated sample volume, calibration curve, extraction efficiency, standard and working gas, water blank, etc.):CFC-12 < 1.8 %CFC-11 < 2.8 %Precision (i.e. mean error from 19 replicate samples):CFC-12 < 0.007 pmol/kg or < 0.9% (which ever is greater) (n=6)We do not give a value for the precision of CFC-11. Offline sample chromatograms regularly show a negative peak in the vicinity of the CFC-11 peak, which decreases the accuracy of CFC-11 in comparison to CFC-12, and which does not allow giving an objective estimate of a precision for CFC-11.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 RH 25/32. We thank Christine Provost, Nathalie Sennechael, Véronique Garçon and the scientific party to participate in the ANT-XXV/4 expedition and for the excellent assistance and cooperation on board. We thank also master and crew of RV Polarstern.Noble gas measurements: Jürgen Sültenfuß; CFC measurements: Klaus BulsiewiczThe tracer data set was carefully checked for accurate measurements and outliers. Quality flags: ? = doubtful; / = bad; # = mean of replicates.

Identifier
DOI https://doi.pangaea.de/10.1594/PANGAEA.787501
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.787501
Provenance
Creator Huhn, Oliver ORCID logo; Rhein, Monika ORCID logo
Publisher PANGAEA
Contributor Institut für Umweltphysik, Universität Bremen
Publication Year 2024
Rights Data access is restricted (moratorium, sensitive data, license constraints)
OpenAccess false
Representation
Resource Type Dataset
Format text/tab-separated-values
Size 2731 data points
Discipline Earth System Research
Spatial Coverage (-66.072W, -62.423S, -56.388E, -55.229N); Drake Passage; Scotia Sea, southwest Atlantic
Temporal Coverage Begin 2009-03-25T13:58:00Z
Temporal Coverage End 2009-04-07T16:51:00Z