Abstract
Abstract. This paper presents and discusses the texture, fabric, water stable isotopes (δ18O, δD) and gas properties (total gas content, O2, N2, Ar, CO2, and CH4 mixing ratios) of two climatically contrasted (Holocene vs. Pleistocene) ice wedges (IW-26 and IW-28) from Cape Mamontov Klyk, Laptev Sea, in northern Siberia. The two ice wedges display contrasting structures: one being of relatively "clean" ice and the other showing clean ice at its centre as well as debris-rich ice on both sides (referred to as "ice-sand wedge"). Our multiparametric approach allows discrimination between three different ice facies with specific signatures, suggesting different climatic and environmental conditions of formation and various intensities and nature of biological activity. More specifically, crystallography, total gas content and gas composition reveal variable levels of meltwater infiltration and contrasting contributions from anaerobic and aerobic conditions to the biological signatures. Stable isotope data are drawn on to discuss changes in paleoenvironmental conditions and in the temporal variation of the different moisture sources for the snow feeding into the ice wedges infillings. Our data set also supports the previous assumption that the ice wedge IW-28 was formed in Pleistocene and the ice wedge IW-26 in Holocene times. This study sheds more light on the conditions of ice wedge growth under changing environmental conditions.
Highlights
Ice wedges are found inside permafrost areas in the Northern Hemisphere and are widespread in Alaska, Canada and Siberia
Ice wedge IW-26 shows δ18O values ranging between −22.6 ‰ and −25.8 ‰ and δD values between −170 ‰ and −191 ‰, respectively (Fig. 4a)
The isotopic composition of ice wedge IW-28 is shown in Fig. 4a, and a clear distinction has to be made between the two different facies of the ice wedge: the ice-sand wedge (ISW-28) and the ice wedge itself (IW-28)
Summary
Ice wedges are found inside permafrost areas in the Northern Hemisphere and are widespread in Alaska, Canada and Siberia. The Pleistocene isotopic signature in the same area clearly differs with values lower by approximately 5 ‰ and 35 ‰ in δ18O and δD, respectively (Popp et al, 2006) showing δ18O/δD values between −33 ‰/−250 ‰ and −31 ‰/−245 ‰ (Wetterich et al, 2008) with minima from the Last Glacial Maximum (−35 ‰/−290 ‰) as documented in a recent overview by Wetterich et al (2011). Meyer et al (2010b), who identified the Younger Dryas cold event in northern Alaskan ice wedges, brought to light
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