Use of stable water isotopes to identify stages of the pingo ice core formation

Abstract

Te isotopic characteristics of the pingo ice cores are considered. Te distribution of δ18O and δ2H values, dexc, δ18O–δ2H and δ2H–d exc relationships, and the simulation of the distribution of δ18O and δ2H values during the ice formation in a closed system, allowed drawing conclusion about the hydrological conditions and stages of the ice core growth. All pingos (Pestsovoye, Weather, Pingo-20) were formed in draining lake basins in the course of freezing of closed taliks. It is established that the water, which served as a source for the formation of the ice core, was subjected to evaporation still before the ice formation. According to our estimates, the water from which the ice of the Pestsovoye pingo was formed was heavier in values of δ18O and δ2H by 3.9 and 29.7‰, respectively, than the current average annual precipitation in the region. Similarly, for the ice of the core of the Pingo Weather it is 2.9 and 14.5‰, and 5.1 and 27.7‰ for the Pingo-20, respectively. In the ice cores of all considered pingos there is an ice formed in a closed system: in Pingo-20 it is a pure injection ice, while in the Pestsovoye and the Weser ones – the injected-segregated ice. Te frost mounds Pestsovoe and Weser grew under changing hydrological conditions: one part of the ice was formed when there was a free flow of water to the freezing front (open system); the other one – when the water-saturated lenses of the closed talik were frozen (closed system). Te isotopic composition of ice being formed under conditions of a closed system reflects isotopic depletion during freezing and ice formation according to the Rayleigh model. It is expressed in a successive decrease in the values of δ18O and δ2H from the frst portions of ice to the last ones as the freezing continued. Te contrast values of δ18O and δ2H in different parts of the ice being formed in the closed system may be used as an additional tool to identify direction of freezing. In a closed system, the last portions of ice have the greater contrast of the isotope values as compared to the frst portions.

Geochemical signatures of pingo ice and its origin in Grøndalen, west Spitsbergen

“…The Grøndalen study area on the western coast of Nordenskiöld Land (west Spitsbergen) is at about 10 km southeast of Barentsburg in whose vicinity the Russian Scientific Arctic Expedition on Spitsbergen Archipelago (RAE-S) maintains ground temperature and active-layer monitoring sites of the Global Terrestrial Network for Permafrost (GTN-P) and the Circumpolar Active Layer Monitoring (CALM) programmes (Demidov et al, 2016;Christiansen et al, 2019). Grøndalen is a trough valley in bedrock of Middle Jurassic-Palaeogene argillite and sandstone (Geological map Svalbard, 1991).…”

“…freezing of a fixed or a (partly) renewed water volume. Estimations of pingo growth rate in Siberia and North America may reach values on the order of decimetres per year (Mackay, 1979;Chizhova and Vasil'chuk, 2018). Assuming the Fili pingo has a similarly fast growth and rather short period of formation, it is likely that there were little to no changes in isotopic composition of the water source.…”

“…Mackay, 1986). Pingo ice and sedimentary inventories were investigated and furthermore employed in palaeoenvironmental reconstructions in the Mackenzie Delta in Canada N. Demidov et al: Geochemical signatures of pingo ice and its origin (Hyvärinen and Ritchie, 1975), on Seward Peninsula in Alaska (Wetterich et al, 2012;Palagushkina et al, 2017), in Siberia (Ulrich et al, 2017;Chizhova and Vasil'chuk, 2018;Wetterich et al, 2018), where they are called bulgunniakhs, and in northern Mongolia (Yoshikawa et al, 2013;Ishikawa and Yamkhin, 2016).…”

Pingo drilling reveals sodium–chloride‐dominated massive ice in Grøndalen, Spitsbergen

“…At Therefore, it is impossible to determine Nori's source water by calculating the mean value of ice core isotopic content as proposed for hydrostatic closed-system pingos (where 100% of water freezes out). 31,32,42 Instead, our calculation is based on the model by Ekaykin et al 43 ; this model utilizes the isotopic trend in ideal closed-system freezing and compares it with the stage A trend (Figure 7). It seems reasonable to conclude that the similarity between the isotopic content of the Oin pingo spring and the modeled Nori pingo groundwater source is not a coincidence and that all Grøndalen pingos had a similar source in the form of a local bicarbonate-dominated Paleogene strata pressurized aquifer that is the source of the Oin pingo outflow.…”

Pingo development in Grøndalen, West Spitsbergen

“…Mackay, 1986). Pingo ice and sedimentary inventories were investigated and furthermore employed in palaeoenvironmental reconstructions in the Mackenzie Delta in Canada (Hyvärinen and Ritchie, 1975), on Seward Peninsula in Alaska (Wetterich et al, 2012;10 Palagushkina et al, 2017), in Siberia (Ulrich et al 2017;Chizhova and Vasil'chuk, 2018;Wetterich et al, 2018), where they are called 'bulgunniakhs', and in northern Mongolia (Yoshikawa et al, 2013;Ishikawa and Yamkhin, 2016).…”