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www.atmos-meas-tech-discuss.net/4/4073/2011/
doi:10.5194/amtd-4-4073-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Water isotopic ratios from a continuously melted ice core sample
1Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
2Physics Institute, Climate and Environmental Physics and Oeschger Centre for Climate Change Research University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
3Science Institute, University of Iceland, Dunhaga 3, 107, Iceland
Abstract. A new technique for on-line high resolution isotopic analysis of liquid water, tailored for ice core studies is presented. We build an interface between an Infra Red Cavity Ring Down Spectrometer (IR-CRDS) and a Continuous Flow Analysis (CFA) system. The system offers the possibility to perform simultaneuous water isotopic analysis of δ18O and δD on a continuous stream of liquid water as generated from a continuously melted ice rod. Injection of sub μl amounts of liquid water is achieved by pumping sample through a fused silica capillary and instantaneously vaporizing it with 100 % efficiency in a home made oven at a temperature of 170 °C. A calibration procedure allows for proper reporting of the data on the VSMOW scale. We apply the necessary corrections based on the assessed performance of the system regarding instrumental drifts and dependance on humidity levels. The melt rates are monitored in order to assign a depth scale to the measured isotopic profiles. Application of spectral methods yields the combined uncertainty of the system at below 0.1 ‰ and 0.5 ‰ for δ18O and δD, respectively. This performance is comparable to that achieved with mass spectrometry. Dispersion of the sample in the transfer lines limits the resolution of the technique. In this work we investigate and assess these dispersion effects. By using an optimal filtering method we show how the measured profiles can be corrected for the smoothing effects resulting from the sample dispersion. Considering the significant advantages the technique offers, i.e. simultaneuous measurement of δ18O and δD, potentially in combination with chemical components that are traditionally measured on CFA systems, notable reduction on analysis time and power consumption, we consider it as an alternative to traditional isotope ratio mass spectrometry with the possibility to be deployed for field ice core studies. We present data acquired in the framework of the NEEM deep ice core drilling project in Greenland, during the 2010 field season.
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Notice on Discussion StatusCitation: Gkinis, V., Popp, T. J., Blunier, T., Bigler, M., Schüpbach, S., and Johnsen, S. J.: Water isotopic ratios from a continuously melted ice core sample, Atmos. Meas. Tech. Discuss., 4, 4073-4104, doi:10.5194/amtd-4-4073-2011, 2011. Bibtex EndNote Reference Manager XML
