Ice-wedge volume calculation in Yedoma and thermokarst deposits

• Main Authors: Ulrich, Mathias, Grosse, Guido, Strauss, Jens, Schirrmeister, Lutz
• Format: Conference Object
• Language: unknown
• Published: University of Lisbon and the University of Évora 2014
• Subjects: Ice; permafrost; Thermokarst; wedge*; Alaska; Siberia
• Online Access: https://epic.awi.de/id/eprint/35775/; https://epic.awi.de/id/eprint/35775/1/EUCOP14_Poster_Ulrich.pdf; http://www.eucop4.org/; https://hdl.handle.net/10013/epic.43700; https://hdl.handle.net/10013/epic.43700.d001

Detailed calculations of ground-ice volumes in permafrost deposits are necessary to understand and quantify the response of permafrost landscapes to thermal disturbance and thawing. Ice wedges with their polygonal surface expression are a widespread ground-ice component of permafrost lowlands. Therefore, the wedge-ice volume (WIV) is one of the major factors to be considered, both for assessing permafrost vulnerability and for quantifying deep permafrost soil carbon inventories. Here, a straightforward tool for calculating the WIV is presented. This GIS and satellite image-based method provides an interesting approach for various research disciplines where WIV is an important input parameter, including landscape and ecosystem modeling of permafrost thaw or organic carbon assessments in deep permafrost deposits. By using basic data on subsurface ice-wedge geometry, our tool can be applied to other permafrost region where polygonal-patterned ground occurs. One is able to include individual polygon geomorphometry at a specific site and the shape and size of epigenetic and/or syngenetic ice wedges in three dimensions. Exemplarily, the WIV in late Pleistocene Yedoma deposits and Holocene thermokarst deposits is calculated at four case study areas in Siberia and Alaska. Therefor, we mapped ice-wedge polygons sizes on different landscape units by using very-high-resolution satellite data. This information was combined with literature or own field data of individual ice-wedge sizes. We demonstrate that the WIV can vary considerably, not only between different permafrost regions, but also within a certain study site. Calculated WIV maxima range from 63.2 vol% to 31.4 vol% in late Pleistocene Yedoma deposits and from 13.2 vol% to 6.6 vol% in Holocene thermokarst deposits in Siberia and Alaska. Maximum WIV can be more than twice as high as calculated minimum WIV at a site. Assuming an equivalent ground-ice thickness (EGIT) from the WIV we are further able to estimate the potential surface subsidence caused by complete thawing of ice wedges. For example, adopting a possible range in Yedoma deposits thickness of 5 to 50 m in northern permafrost regions, the EGIT related to our calculated WIV maximum would range from 3.2 m to 31.6 m, respectively. In accordance to possible thermokarst deposit thicknesses of 1 to 10 m, the maximum WIV calculated for Holocene thermokarst deposits corresponds to an EGIT of 0.1 to 2.0 m, respectively.