Stable isotope dynamics in a seasonally changing snow cover on Samoylov Island, Northern Siberia

• Main Author: Boehm, Erik
• Format: Thesis
• Language: unknown
• Published: 2014
• Subjects: Ice; lena delta; permafrost; wedge*; Siberia
• Online Access: https://epic.awi.de/id/eprint/39008/; https://epic.awi.de/id/eprint/39008/1/Boehm_BSc-Arbeit_S.pdf; https://hdl.handle.net/10013/epic.46241; https://hdl.handle.net/10013/epic.46241.d001

While climate change takes place world-wide, the Artic regions are very sensitive to these changes while influencing the biodiversity of the whole world. Therefore, climate archives are considered to better understand the climate of the past. In permafrost regions, covering about 24% of the northern hemisphere land surface, established climate archives such as ice caps, deep lake sediments or tree rings are rarely found. On the other hand, the ground ice contained in permafrost soils is expected to provide paleoclimatic information. Ice wedges, vertically-foliated or –banded wedge-shaped ice bodies, are considered the most appropriate type of ground ice for climate reconstructions. They form mainly by the penetration and refreezing of snow melt water in open frost cracks in early spring, resulting in annual layers which are expected to contain the temperature signal of the year of their formation. To understand the paleoclimatic signal preserved in the climate archive “ice wedge”, it is necessary to identify its source. For this purpose, a study on the spatial and temporal variability of the thickness and the isotopic composition of a snow cover during spring was carried out at Samoylov Island within the Lena Delta. Snow samples were collected at different geomorphologic units of different ice-wedge polygons and at a snow field and their isotopic composition has been correlated with weather data from Samoylov Island in order to identify annual cycles and predominant alteration processes. It was difficult to characterize an annual cycle while it was possible to identify a late warm phase in late autumn and a late cold phase in early spring. It was observed that that the snow cover and its isotopic composition undergo changes over time due to sublimation, evaporation and wind drift processes. Percolating rain water highly reduced the thickness of the snow cover but had no significant influence on its isotopic composition, while the collection of initial-snow-melt-runoff water leads to a higher concentration of lighter isotopes in the polygon centers. It has been shown that the climate signal preserved in ice wedges is derived from early spring temperatures, as its isotopic composition best corresponds with that of snow from the bottom of the snow cover, depth hoar and ice out of snow melt water developing in the troughs above frost cracks, while showing an influence of moisture of precipitation of the previous summer period.