ИСТИНА

In this contribution we present stable-water isotope data of ice wedges from the Oyogos Yar coast of the Dmitry Laptev Strait (72.7°N, 143.5°E). Based on our chronology the studied ice wedges correspond to different stratigraphic units of the Late Quaternary. These are (1) an Ice Complex of MIS5 age, (2) Early Weichselian (MIS4 to MIS3) flood plain deposits, (3) the Middle Weichselian Yedoma Ice Complex of MIS3 age and (d) Holocene themokarst deposits. An ice wedge of the MIS5 Ice Complex exhibits mean δ18O and d excess values of -33‰ and 7‰, respectively, representing very cold winter temperatures. Small multi-stage ice wedges corresponding to the MIS4 to MIS3 flood plain deposits showed two clusters of isotope values: (1) in their lower parts, i.e. composite sand-ice wedges or “polosatics”, δ18O values of -31 to -28‰ (d excess of 0-5‰) and (2) in their upper parts (classical ice wedge) δ18O values of -34‰ (d excess of 5‰), reflecting rather different formation conditions than climate differences under very cold climate conditions. The huge syngenetic ice wedges of the Weichselian Yedoma Ice Complex (MIS3) are characterized by mean δ18O values of -33‰ to -29‰ and mean d-excess values between 4 and 8‰ corresponding to different altitude levels and reflecting cold to very cold winter temperatures. On top of the Ice Complex as well as in a thermokarst depression of Late Glacial origin, Holocene ice wedges could be found. They have been grown predominantly in the Middle to Late Holocene and exhibit mean δ18O values of about -25‰ and mean d-excess values of 8‰, mirroring distinctly warmer winter temperatures in the Holocene. Recently grown (modern) ice wedges of the last decades are characterized by mean δ18O values of about -21‰ and mean d excess values of 8‰, testifying the recent winter warming in the Arctic.