Gravimetric ice content of sediment samples and stable isotope characteristics for ice wedges and for pore and segregrated ice at the Oyogos Yar coast, Northeast Siberian Arctic

To reconstruct palaeoclimate and palaeonvironmental 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 the Marine Isotope Stage (MIS) 5. Ground ice 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 proxy for past winter climate conditions covers about 200 thousand 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 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 the MIS5c and by Holocene ice-wedge stable-isotopes. Modern ice-wedge stable isotopes are most enriched and testify the recent winter warming in the Arctic. Hence, ice-wedge based reconstructions of changes in winter climate conditions add substantial information to those derived from paleoecological proxies stored in permafrost and allow for distinguishing 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.为重建东北西伯利亚北极区域的古气候与古环境，我们针对奥约戈斯亚尔海岸（Oyogos Yar Coast）——即德米特里·拉普捷夫海峡（Dmitry Laptev Strait）区域——的晚第四纪多年冻土展开研究。本次获取了库奇古伊组（Kuchchugui Suite）典型河漫滩沉积物以及克列斯特尤里亚赫组（Krest Yuryakh Suite）热融湖沉积物的全新红外激发光释光（infrared stimulated luminescence）年代数据，分别为112.5±9.6 kyr与102.4±9.7 kyr，为德米特里·拉普捷夫海峡地区海洋同位素阶段（Marine Isotope Stage，简称MIS）5期的地貌演化历史提供了可靠的年代学数据，并阐明了该区域的地貌发育历程。 本文同时呈现了8个冰地层单位的地下冰稳定同位素数据与冰岩性信息，并补充了邻近的大利亚霍夫斯基岛（Bol'shoy Lyakhovsky Island）的相关观测数据。我们整合的冰楔稳定同位素记录作为古冬季气候的代用指标，时间跨度约为20万年；此外还补充了孔隙冰与分凝冰的稳定同位素数据，此类数据反映了受冻结作用叠加改造的年际气候状况。 我们的冰楔稳定同位素数据表明，晚第四纪东北西伯利亚北极地区的冬季气候存在显著波动，这一差异不仅体现在冰期与间冰期之间，也存在于近千年至近百年的时间尺度上。冰楔复合体（Ice Complex）的冰楔稳定同位素值显示：约20万年前（MIS7）的冬季气温处于寒冷至极寒状态，约10万年前（MIS5）的冬季气候极为寒冷，约6万至3万年前的冬季气温介于极寒与温和之间，而末次冰盛期（Last Glacial Maximum，MIS2）的冬季气温则极度严寒。MIS5c时期广泛发育的热融地貌以及全新世冰楔稳定同位素数据均反映出当时冬季气候更为温暖。现代冰楔稳定同位素组成最为富集，证实了北极地区近期出现的冬季变暖现象。 因此，基于冰楔的冬季气候变化重建结果，可为多年冻土中保存的古生态代用指标提供重要补充，且能够区分古气候动力学的季节变化趋势。未来若能在冰楔定年技术上取得进展，并提升冰楔衍生气候信息的时间分辨率，将有助于充分挖掘冰楔的古气候研究潜力。