Ground-ice stable isotopes and cryostratigraphy reflect late Quaternary palaeoclimate in the Northeast Siberian Arctic (Oyogos Yar coast, Dmitry Laptev Strait)

Abstract

Abstract.To reconstruct palaeoclimate and palaeoenvironmental conditions in the northeast Siberian Arctic, we studied late Quaternary permafrost at the Oyogos Yar coast (Dmitry Laptev Strait). New infrared-stimulated luminescence ages for distinctive floodplain deposits of the Kuchchugui Suite (112.5 ± 9.6 kyr) and thermokarst-lake deposits of the Krest Yuryakh Suite (102.4 ± 9.7 kyr), respectively, provide new substantial geochronological data and shed light on the landscape history of the Dmitry Laptev Strait region during Marine Isotope Stage (MIS) 5. Groundice stable-isotope data are presented together with cryolithological information for eight cryostratigraphic units and are complemented by data from nearby Bol'shoy Lyakhovsky Island. Our combined record of ice-wedge stable isotopes as a proxy for past winter climate conditions covers about 200 000 years and is supplemented by stable isotopes of pore and segregated ice which reflect annual climate conditions overprinted by freezing processes. Our ice-wedge stable-isotope data indicate substantial variations in northeast Siberian Arctic winter climate conditions during the late Quaternary, in particular between glacial and interglacial times but also over the last millennia to centuries. Stable isotope values of ice complex ice wedges indicate cold to very cold winter temperatures about 200 kyr ago (MIS7), very cold winter conditions about 100 kyr ago (MIS5), very cold to moderate winter conditions between about 60 and 30 kyr ago, and extremely cold winter temperatures during the Last Glacial Maximum (MIS2). Much warmer winter conditions are reflected by extensive thermokarst development during MIS5c and by Holocene ice-wedge stable isotopes. Modern ice-wedge stable isotopes are most enriched and testify to the recent winter warming in the Arctic. Hence, ice-wedgebased reconstructions of changes in winter climate conditions add substantial information to those derived from paleoecological proxies stored in permafrost and allow a distinction between seasonal trends of past climate dynamics. Future progress in ice-wedge dating and an improved temporal resolution of ice-wedge-derived climate information may help to fully explore the palaeoclimatic potential of ice wedges.

Ice wedges as archives of winter paleoclimate: A review

“…Ice wedges probably include some of the oldest ice preserved in the Arctic. Ages of about 200 000 years from Bol'shoy Lyakhovsky Island in the eastern Siberian Arctic and more than 700 000 years from Yukon, Canada, have been reported. Ice wedges from the last glacial period are abundant in permafrost sequences across the Arctic, in particular in northern Siberia, Alaska and Canada.…”

“…At high latitudes, the stable‐isotope ratios of oxygen and hydrogen (δ 18 O and δD) in precipitation are sensitive to local air temperatures . Ice wedges in Siberia, Canada, Alaska, Svalbard and China have been studied as they preserve δ 18 O and δD values over centennial to millennial timescales, which additionally allow calculation of the second‐order parameter deuterium excess d ( d = δD − 8*δ 18 O) . In spring, frost cracks may fill mostly with melt water from the last winter's snow pack, whose integrated isotopic signal is transferred into a single ice vein without additional isotopic fractionation due to rapid freezing in the frozen ground .…”

“…Previous paleoclimate studies of ice wedges have covered different timescales of the late Quaternary. Due to syngenetic ice‐wedge growth—often over tens of thousands of years—and limited dating methods, the temporal resolution of ice‐wedge paleoclimate studies is often very low and corresponds to specific stratigraphic units of the Late Pleistocene and the Holocene, depending on the dating techniques applied …”

“…Currently, the ages of ice wedges are determined either indirectly by dating of host sediments or by direct dating of the wedges themselves. The indirect approach attributes ice wedges to stratigraphic units and dates the host sediments using radiocarbon, radioisotope disequilibrium, luminescence, or fission‐track dating of tephra . However, the temporal relationship of ice wedges to dated host sediments is complex and variable.…”

Isotopic evidence for Holocene January air temperature variability on the East Chukotka Peninsula

“…Permafrost archives can be a valuable source for winter paleoclimate reconstructions as oxygen and hydrogen stable isotope signatures of ice‐wedges reflect climatic changes . The 18 O and 2 H composition of ice‐wedge ice is a function of the isotopic signature of the contributing sources, the proportions contributed from each of them, and the isotopic changes (by mixing and fractionation) during either freezing or by diffusion after freezing.…”