Ice-wedge ice is one of the natural archives reflecting climatic changes. Direct AMS 14C dating of ice-wedge ice enable for comparison of their stable isotope contents with those in polar ice. Ice wedges, however, cover a shorter time span than ice cores. By means of AMS 14C-dating, paleoenvironmental proxies from ice wedges can be "stacked".
Variations of stable isotope ratios in ice wedges are similar to those in the ice cores. The range of d18O values from ice-wedge ice indicating winter temperatures.
Several different materials were dated in the ice wedges, such as organic micro inclusions and pollen concentrates. The difference between the alkaline and organic fractions ranges from 1100 years to more than 7900 years. Correlations between 14C-dates of pollen concentrates, re-deposited pollen and spores are observed. The youngest date corresponds to the minimum amount of re-deposited pollen and spores. This means that the alkaline fraction and pollen concentrate often contain ancient organic material. The micro organic 14C AMS dates were the base of the age setting, because such inclusions most likely originated from contemporaneous plant material.
For the Seyaha cross-section (Yamal Peninsula), the 14C dates range from 22.400 to 25.200 BP, delta18O values range from –25.0 to –20.4‰. For Zelyony Mys (Kolyma River) the 14C dates range from 13.600 to 28.400 BP, delta18O values range from –34.1 to –29.4‰. For Duvanny Yar (Kolyma River) the 14C dates - 14.100 to 25.400 BP, delta18O values range from –32.7 to –28.7‰. For Plakhinski Yar (Kolyma River) the 14C dates - 11.500 to 21.400 BP, delta18O values range from –34.7 to –28.7‰. For Bison (Kolyma River) the 14C dates - 43.600 to 26.200 BP delta18O values range from –33.79 to –28.7‰. For Mamontova Gora (Aladan River) the 14C dates - 13.900 to 18.400 BP, delta18O range from –29.4 to –25.9‰. For Phoenix (Magadan Region) the youngest 14C date is 11000 ± 80; delta18O values range from –32.6‰ to –24.9‰.
The most expressed negative isotopic shifts are observed between 16.5-14 and 11-12 kyr BP. In all plots from each ice wedge system could be separate from 3 to 7 episodes correlating with Dansgaard-Oeschger events lasting 1-2.5 kyr. The AMS dates yields a precise age of the observed stable isotope shift. The ice wedge records for Northern Siberia are consistent and are important in providing a chronological framework for this region. A ~1500 yr cycle characterizing both the Greenland ice sheet and Siberian ice wedges is observed.
See more of Poster Session I
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)