Stable oxygen and hydrogen isotope compositions of the Messoyakha and Pestsovoe pingos in northwest Siberia as markers of ice core formation

Pingos are indicators of modern and past conditions of permafrost. In total, 1,620 pingos have been identified on the Yamal and Gydan peninsulas in western Siberia. The main purpose of this study is to consider the distribution of stable isotopes in pingo ice cores formed under conditions of open and closed systems. Two pingos from ice cores of different origin in the continuous permafrost zone of northwest Siberia have been considered: the Messoyaha-1 pingo (10.5 m in height) and the Pestsovoe pingo (17 m in height). Drilling of the ice core was performed with continuous sampling of an undisturbed frozen core. Ice formation was estimated according to the Rayleigh fractionation in a closed-system versus an open-system framework. For the Pestsovoe pingo, a pronounced decrease in delta O-18 values with corresponding increase in d(exc) with depth indicates a closed system upon freezing of the lake talik from the top down. For the Messoyakha-1 pingo, the values of delta O-18 and delta H-2 showed a weak tendency to decrease with depth, with values of d(exc) varying randomly. Ice that was segregated in the overlying and underlying sediments had similar values of delta O-18 and delta H-2 and a low slope. Isotopically nonequilibrium ice formation was established for ice which had been segregated in a closed system and for ice cores formed in an open to semiclosed system. The vacuum mechanism of water suction from the surrounding lake or lake talik may have played a significant role during the formation of the upper ice core of the Messoyakha-1 pingo and its additional growth.

Automated summary

This study investigates the distribution of stable isotopes in ice cores of two pingos in northwest Siberia, revealing that the Pestsovoe pingo formed under a closed system while the Messoyakha-1 pingo exhibited isotopically nonequilibrium ice formation. The formation process of the ice cores suggests the involvement of a vacuum mechanism in water suction from surrounding lake or talik during the growth of the Messoyakha-1 pingo.