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.

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.

Dating of ancient permafrost is essential for understanding long-term permafrost stability and interpreting palaeoenvironmental conditions but presents substantial challenges to geochronology. Here, we apply four methods to permafrost from the megaslump at Batagay, east Siberia: (1) optically stimulated luminescence (OSL) dating of quartz, (2) post-infrared infrared-stimulated luminescence (pIRIR) dating of K-feldspar, (3) radiocarbon dating of organic material, and (4) 36Cl/Cl dating of ice wedges. All four chronometers produce stratigraphically consistent and comparable ages. However, OSL appears to date Marine Isotope Stage (MIS) 3 to MIS 2 deposits more reliably than pIRIR, whereas the latter is more consistent with 36Cl/Cl ages for older deposits. The lower ice complex developed at least 650 ka, potentially during MIS 16, and represents the oldest dated permafrost in western Beringia and the second-oldest known ice in the Northern Hemisphere. It has survived multiple interglaciations, including the super-interglaciation MIS 11c, though a thaw unconformity and erosional surface indicate at least one episode of permafrost thaw and erosion occurred sometime between MIS 16 and 6. The upper ice complex formed from at least 60 to 30 ka during late MIS 4 to 3. The sand unit above the upper ice complex is dated to MIS 3–2, whereas the sand unit below formed at some time between MIS 4 and 16.

Late Quaternary landscapes of unglaciated Beringia were largely shaped by ice-wedge polygon tundra. Ice Complex (IC) strata preserve such ancient polygon formations. Here we report on the Yukagir IC from Bol'shoy Lyakhovsky Island in northeastern Siberia and suggest that new radioisotope disequilibria (230Th/U) dates of the Yukagir IC peat confirm its formation during the Marine Oxygen Isotope Stage (MIS) 7a–c interglacial period. The preservation of the ice-rich Yukagir IC proves its resilience to last interglacial and late glacial–Holocene warming. This study compares the Yukagir IC to IC strata of MIS 5, MIS 3, and MIS 2 ages exposed on Bol'shoy Lyakhovsky Island. Besides high intrasedimental ice content and syngenetic ice wedges intersecting silts, sandy silts, the Yukagir IC is characterized by high organic matter (OM) accumulation and low OM decomposition of a distinctive Drepanocladus moss-peat. The Yukagir IC pollen data reveal grass-shrub-moss tundra indicating rather wet summer conditions similar to modern ones. The stable isotope composition of Yukagir IC wedge ice is similar to those of the MIS 5 and MIS 3 ICs pointing to similar atmospheric moisture generation and transport patterns in winter. IC data from glacial and interglacial periods provide insights into permafrost and climate dynamics since about 200 ka.