Land-atmosphere interactions during winter at a permafrost site in Northern Siberia with a focus on water vapor isotopic composition

• Main Author: Schmidt, Toni
• Format: Thesis
• Language: unknown
• Published: Universität Potsdam 2017
• Subjects: Ice; lena delta; lena river; permafrost; Siberia
• Online Access: https://epic.awi.de/id/eprint/48643/; https://epic.awi.de/id/eprint/48643/1/Schmidt2017.pdf; https://hdl.handle.net/10013/epic.3cbcf80f-5227-4c51-a97a-ecb4b4219210

Land and atmosphere processes influence the isotopic composition of water vapor during winter. Depending on climatic conditions, stable isotope fractionation occurs during each phase change. Thus, isotopes are valuable proxies for air temperatures and tracers of atmospheric moisture. Hourly data records from 01 July 2015 to 30 June 2016 of meteorological and soil parameters and of water vapor isotopic composition from Samoylov Island, Lena Delta, Siberia at 72°22’ N, 126°29’ E, were investigated to observe local environmental processes during winter and correlations between land, atmosphere, and water vapor isotopes. Winter was defined by the presence of snow (23 September 2015 to 15 May 2016). During winter, water is present in gaseous, liquid, and solid state. The latter was identified in frozen ground, as the active layer froze from 21 October 2015 to 05 June 2016, and on water bodies, as Molo Lake on Samoylov Island had an ice cover from 29 September 2015 to 21 June 2016 and the Lena River had an ice cover from 07 October 2015 to 06 June 2016. Liquid water was though available under the ice cover of Molo and the Lena River. The air was with a mean specific humidity of 1.4 g/kg very dry during winter. Also both δ18O and δD were very low during winter, with means of -41.3‰ for δ18O and -299.6‰ for δD. But large ranges of δ18O and δD were especially observed during four periods of long-term peaks with δ values up to -27.4‰ for δ18O and -201.0‰ for δD on 27 April 2016. This variability is mostly caused by changes of local air temperatures and humidity levels. With 30.4‰, a high mean of deuterium excess during winter provides information about low humidity conditions and strong kinetic fractionation at evaporation and sublimation at the moisture source location. A slope of 7.4 for the δD-δ18O correlation during winter suggests local moisture sources. These results show the possibility to explain water vapor isotopic composition with local land and atmosphere processes with the existing data. Additionally, the ...