Holocene January paleotemperature of northwestern Siberia reconstructed based on stable isotope ratio of ice wedges

Abstract

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 δ 18 O 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 (T mJ ) varied between À21 and À30 C, and from the end of the Northgrippian, during the Meghalayan stages of Holocene (5.2-0.9 cal ka BP), T mJ varied between À24 to À28 C. Mean January air temperature during the Holocene was generally 1-2 C lower than the modern one, meanwhile the submeridional direction of T mJ isotherms and eastward decrease of T mJ values in Holocene are similar to the modern pattern.

Early Holocene Oxygen Isotope Chronologies (11,267–6420 Cal Bp) From Ice Wedge at Chara, Transbaikalia

“…The obtained results allow us to consider active and widespread syngenetic permafrost aggradation in the Northern Transbaikalia in the Holocene, including the optimum period, which is supported by data obtained for both neighboring and distant regions. For example, ice wedges in the Holocene deposits were studied by Popp et al (2006) in the coastal outcrop of the upper Tumara River, central Yakutia and by Vasil’chuk et al (2023) in northwestern Siberia.…”

“…A 14 C age of 7.46 cal ka BP was identified in the peat above the ice wedge near Seyakha village on the eastern coast of the Yamal Peninsula, and a 10.49 cal ka BP age has been identified near the ice wedge’s “tail”. Here, ice wedges were formed following the late Greenlandian to early Northgrippian stages of the Holocene (Vasil’chuk et al 2023).…”