Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 1207-1225, 2017
http://www.atmos-chem-phys.net/17/1207/2017/
doi:10.5194/acp-17-1207-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
25 Jan 2017
The influence of snow sublimation and meltwater evaporation on δD of water vapor in the atmospheric boundary layer of central Europe
Emanuel Christner1,2, Martin Kohler1, and Matthias Schneider2 1Institute of Meteorology and Climate Research – Department Troposphere (IMK-TRO), Karlsruhe Institute of Technology (KIT), Germany
2Institute of Meteorology and Climate Research – Department Atmospheric Trace Gases and Remote Sensing (IMK-ASF), Karlsruhe Institute of Technology (KIT), Germany
Abstract. Post-depositional fractionation of stable water isotopes due to fractionating surface evaporation introduces uncertainty to various isotope applications such as the reconstruction of paleotemperatures, paleoaltimetry, and the investigation of groundwater formation. In this study, we investigate isotope fractionation at snow-covered moisture sources by combining 17 months of observations of isotope concentration ratios [HD16O] ∕ [H216O] in low-level water vapor in central Europe with a new Lagrangian isotope model. The isotope model is capable of reproducing variations of the observed isotope ratios with a correlation coefficient R of 0.82. Observations from 38 days were associated with cold snaps and moisture uptake in snow-covered regions. Deviations between modeled and measured isotope ratios during the cold snaps were related to differences in skin temperatures (Tskin). Analysis of Tskin provided by the Global Data Assimilation System (GDAS) of the NCEP implies the existence of two regimes of Tskin with different types of isotope fractionation during evaporation: a cold regime with Tskin < Tsubl,max = −7.7 °C, which is dominated by non-fractionating sublimation of snow, and a warmer regime with Tsubl,max < Tskin < 0 °C, which is dominated by fractionating evaporation of meltwater. Based on a sensitivity study, we assess an uncertainty range of the determined Tsubl,max of −11.9 to −2.9 °C. The existence of the two fractionation regimes has important implications for the interpretation of isotope records from snow-covered regions as well as for a more realistic modeling of isotope fractionation at snow-covered moisture sources. For these reasons, more detailed experimental studies at snow-covered sites are needed to better constrain the Tsubl,max and to further investigate isotope fractionation in the two regimes.

Citation: Christner, E., Kohler, M., and Schneider, M.: The influence of snow sublimation and meltwater evaporation on δD of water vapor in the atmospheric boundary layer of central Europe, Atmos. Chem. Phys., 17, 1207-1225, doi:10.5194/acp-17-1207-2017, 2017.
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Short summary
Post-depositional fractionation of stable water isotopes due to fractioning surface evaporation introduces uncertainty to isotope applications such as the reconstruction of paleotemperatures, paleoaltimetry, and the investigation of ground water formation. In this paper we combine measurements of stable water isotopes in near-surface water vapor with a Lagrangian isotope model to investigate isotope fractionation during the evaporation of surface-layer snow in central Europe.
Post-depositional fractionation of stable water isotopes due to fractioning surface evaporation...
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