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Studies of permafrost agradation within peat mires leading to palsa growth and palsa dynamics during the Holocene are important for predicting the future of permafrost in a changing climate. The radiocarbon age of peat cover and stable isotope composition of the ice cores of palsas near Eletsky settlement, north‐east of the European part of Russia, were studied. Palsa growth was the most active between 8 and 5 cal ka BP. The main sources for ice core formation were precipitation‐fed surface and suprapermafrost waters. It is assumed that the isotope composition of the initial water was isotopically depleted compared with modern surface waters, which may be explained by general climate cooling during earlier stages of palsa growth (response to the 8.2 ka cooling event). The ice cores of the studied palsas were formed during the freezing of water in semi‐closed conditions, mainly by the segregation mechanism during permafrost agradation, thickness of the ice lenses and ice volume could depend on freezing rates and water supply. The upper part of the palsa ice core experienced deep thawing and could be saturated with meteoric water; repeated freezing of this part of the ice core likely occurred in closed system conditions. [ABSTRACT FROM AUTHOR]

The purpose of the study is to compare the results of the stable isotope analysis (δ18O, δ2H, and deuterium excess values) of parallel and synchronous ice wedges exposed in one outcrop in the upper part of the Batagay Yedoma (67.58° N, 134.77° E) and to estimate their precision, that is, a measure of similarity of independent isotope results of two ice wedges. Detailed sampling of two syngenetic ice wedges (IW‐17 and IW‐20) for isotope analysis was carried out in the exposure of the thermo‐erosional ravine in the southeastern part of the Batagay megaslump. In total, results of 105 measurements for IW‐17 and 59 measurements for IW‐20 were obtained. According to 14C AMS ages of organic microinclusions in the ice‐wedge ice, the studied ice wedges began to form no later than 42 cal ka BP. The termination of their growth was dated to about 11.7 cal ka BP. For both ice wedges, generally low isotope values were obtained. For the IW‐17, the mean values are −34.38‰ for δ18O, −264.82‰ for δ2H, and 10.2‰ for dexc. For IW‐20, the mean isotope values are −34.09‰ for δ18O, −262.91‰ for δ2H, and 9.84‰ for dexc. Statistical tests showed significant correlations between the isotope data in the upper parts of ice wedges that may be explained by similar conditions during their growth at this stage. Our results allow us to refine the solutions to the two main issues studied of the Late Pleistocene Yedoma: the age of the ice wedges, the accuracy of the isotope profiles, and the paleotemperature interpretation of the isotope records. [ABSTRACT FROM AUTHOR]

Accelerator mass spectrometry radiocarbon (AMS 14C) dating was used for determining the age of wedge ice. It has been found that between 11,270 and 6420 cal BP, or the Greenlandian and Northgrippian stages of the Holocene, ice wedges grew syngenetically in sandy deposits with gravel in the Chara River valley. The variations of δ18O values in the ice wedges are about 8‰, from –25.5‰ to –18.8‰. Based on the stable isotope composition of ice wedges, paleotemperature reconstructions revealed that the mean January temperature was as low as –38°C during the coldest periods of the early half of the Holocene and as high as –28°C during the warmer periods. [ABSTRACT FROM AUTHOR]

The Eastern Chukotka is considered a unique permafrost region where massive ice bodies are widespread. However, the origin and age of these ice formations are often discussed. The age of the massive ice of Chukotka was established for the first time using AMS 14C dating. It was revealed that three massive ice bodies on the coast of Mechigmen Bay were formed at the end of the Late Pleistocene: a) near the Akkani site, 21,612 to 22,147 cal BP; b) near the Lavrentiya settlement, 27,553 cal BP; and c) near the Lavrentiya settlement, 22,193 cal BP. Stable isotope values in the studied massive ice vary in a rather wide range by about 10‰ for δ18O values (from –14.8‰ to –24.5‰) and about 75‰ for the δ2H values (from –116‰ to –191‰). The studied massive ice bodies are of intrasedimental genesis and formed epigenetically during the final stage of MIS2 (22–27 cal ka BP). [ABSTRACT FROM AUTHOR]

Yedoma ice complex sediments with large syngenetic ice wedges (IW) are usually observed in outcrops in river valleys on permafrost plains and on sea coasts and lake shores in the north of Siberia, Alaska, and Canada. Less frequently, they occur in mountainous and foothill regions of East Siberia, for example, in the Upper Kolyma Upland and in river valleys of the Eastern Sayan Range and the Anabar Plateau, as well as in Alaska and Yukon. The author's materials on gravelly Yedoma with IWs in the intermountain basins, on mountain slopes, and on sea coasts and lake shores are presented. The obtained data allow a conclusion that gravelly Yedoma has mainly alluvial, lacustrine, and colluvial origins with an insignificant participation of aeolian processes. Occurrence of the late Pleistocene gravelly deposits with large syngenetic IWs confirms a hypothesis of polygenetic origin of Yedoma. [ABSTRACT FROM AUTHOR]

Ice wedges are considered as a paleoarchive of winter air temperatures as their stable isotope composition has been widely used to reconstruct winter climatic conditions in the Arctic regions. Ice wedge stable isotope records, obtained in recent decades for many Arctic permafrost areas of Russia and North America, demonstrate a clear shift from lower to higher values between the Late Pleistocene and Holocene (by 5–10‰ for δ18O values in some regions of the Russian Arctic), which is widely accepted as evidence of winter air temperature increase. However, the evolution of winter air temperatures during the Holocene is less clear and, according to proxy reconstructions, winter climate trends are not synchronous and may significantly vary throughout the Arctic. In this study, we investigate the stable isotope composition of Holocene syngenetic ice wedges and modern ice veinlets of northwestern Siberia. Radiocarbon dating of enclosing sediments and a few dates of organic material from ice wedges demonstrate that ice wedges grew constantly within the study area during the Holocene though early–mid‐Holocene in northwestern Siberia is often considered as a thermal optimum. In fact, many proxy records indicate an increase of summer air temperatures followed by thermokarst activity, peatland formation, and northward advance of the treeline. According to our data, winter climate conditions in terms of mean air temperature of the coldest winter month (January) did not change significantly during the key Holocene stages, and during the Greenlandian and most of the Northgrippian stages (between 11.4 and 6 cal ka BP) mean January air temperature (TmJ) varied between −21 and −30°C, and from the end of the Northgrippian, during the Meghalayan stages of Holocene (5.2–0.9 cal ka BP), TmJ varied between −24 to −28°C. Mean January air temperature during the Holocene was generally 1–2°C lower than the modern one, meanwhile the submeridional direction of TmJ isotherms and eastward decrease of TmJ values in Holocene are similar to the modern pattern. [ABSTRACT FROM AUTHOR]

The recently formed Batagay mega-thaw slump exposes permafrost deposits to a depth of up to 92 m below ground surface and provides insight into the climate record in the region of the most severe continental climate in the Northern Hemisphere. Radiocarbon and stable isotope data were obtained to verify the age of ice wedges in the Batagay yedoma (upper Ice Complex in the local cryostratigraphy), and to deduce paleoclimate information. A millennial-scale resolution paleotemperature record from radiocarbon-dated ice wedges spans Marine Isotope Stages (MIS) 3–2. The Batagay mean January air paleo-temperature during the 44.9–42 and 30.8–27.1 cal ka BP periods was stable cold has been reconstructed to about –51 ± 3°C each. [ABSTRACT FROM AUTHOR]

Yedoma sediments with thick syngenetic ice wedges have been studied on the Yamal Peninsula, northwestern Siberia. The accumulation of yedoma strata occurred under alternating subaqueous-subaerial conditions, and three tiers of ice wedge were formed mainly on subaerial stages. The ice wedges and enclosing sediments were dated, revealing that the ice wedges were formed between 29 and 18 cal ka BP, while the enclosing sediments are generally older, possibly due to contamination with ancient material (especially in the central part of the yedoma). However, the termination of yedoma complex formation was dated not later than 13.5 cal ka BP. Stable oxygen-isotope data for the ice wedges indicate more severe winter climate conditions during 25–21 cal ka BP, when mean January air temperatures were at least 10°C lower that modern ones, favoring syngenetic ice wedge growth. Yedoma accumulation in the western part of northern Siberia does not support the existence here of an ice sheet during the LGM. [ABSTRACT FROM AUTHOR]