Ice wedge polygon development on different temporal and spatial scales in the northern Yukon, Canada

• Main Authors: Fritz, Michael, Wolter, Juliane, Rudaya, Natalia, Palagushkina, Olga, Nazarova, Larisa, Krautblatter, Michael, Obu, Jaroslav
• Format: Conference Object
• Language: unknown
• Published: Terra Nostra – Schriften der GeoUnion Alfred-Wegener-Stiftung 2015/1 2015
• Subjects: Ice; permafrost; Talik; Tundra; wedge*; Yukon
• Online Access: https://epic.awi.de/id/eprint/37965/; http://www.awi.de/fileadmin/user_upload/Research/Research_Divisions/Geosciences/Periglacial_Research/Events/PastGateways2015/PastGateways-Abstractband-Screen-Final3.pdf; https://hdl.handle.net/10013/epic.45525

Ice wedge polygons (IWP) are amongst the most typical permafrost phenomena in Arctic lowlands. Within the northern hemisphere, IWP are thought to occupy between 250,000 km² (Minke et al., 2007) and 2,600,000 km² (Mackay 1972) of the tundra and boreal forest, which accounts for 3 to 31% of the arctic land mass including glaciated regions. Besides the wide spatial distribution, IWP have stored large quantities of organic carbon and nitrogen on geological timescales and are therefore regarded as greenhouse gas sinks. Continuous organic matter accumulation and preservation due to syngenetic permafrost aggradation make arctic polygon mires an excellent climate and environmental archive. Here we present the results of a multidisciplinary palaeoenvironmental study on IWP in the northern Yukon, Canada. High-resolution laboratory analyses were carried on a permafrost core together with the overlying active layer (233 cm length) which was drilled in 2012. Based on 14 AMS radiocarbon dates spanning the last 5,000 years, we report high-resolution ground ice stratigraphy, stable water isotopes (δ18O, δD), sedimentary data including grain size distribution and biogeochemical parameters (OC, N, C/N ratio, δ13C), as well as pollen and diatom assemblages. This is accompanied by high-resolution remote sensing data based on airborne LIDAR and on underground investigations using electrical resistivity tomography in different resolutions. The studied low-centered IWP indicates that the whole IWP field was established after a shallow lake had drained at about 3200 cal BP. The diatom assemblage in the lower part of the sedimentary record is dominated by planktonic and pioneer species and by those preferring alkaline conditions. Ice-wedge cracking in water-saturated sediments started immediately after lake drainage and led to the formation of a polygon mire. Downward closed-system freezing of the talik is indicated by continuously decreasing δ18O (δD) values, a δ18O/δD-regression-slope below the Global Meteoric Water Line and a ...