Reconstruction of glacier fluctuations in the East Sayan, Baikalsky and Kodar Ridges (East Siberia, Russia) during the last 210 years based on high-resolution geochemical proxies from proglacial lake bottom sediments

摘要

We have presented results of study of bottom sediments of the proglacial lakes enriched with meltwater of Peretolchin Glacier (the East Sayan Ridge), Chersky Glacier (the Baikalsky Ridge) and glaciers of the Kodar Ridge. Bottom sediments formed from the end of the Little Ice Age to 2013 were investigated with time resolution in year-season, using X-ray fluorescence with synchrotron radiation and inductively coupled plasma mass spectrometry. Depth-age models of the cores were estimated from year laminate layers, using Pb-210 and Cs-137 chronology. Intense glacier thawing was calculated from the amount of clastic matter supplied by glacier meltwater into proglacial lakes. A high content of some elements was closely associated with clastic material (e.g. Rb, Zr, Nb, Y or Th) in bottom sediments, and most likely these elements affected the intensity of glacier melting. We have defined three periods in significant increase of glacier flow/melting during the last 210 years. The first period (ca. 1800-1890), supply of suspended material by meltwater into Lake Ekhoy (the East Sayan Ridge) and Lake Preobrazhenskoe (the Kodar Ridge), was not intense until 1850 and 1875, respectively. However, the rate of meltwater supply into Lake Izumrudnoe (the Baikalsky Ridge) was high during the Little Ice Age, and it is likely attributed to local moisture from Lake Baikal. The regional glacier water balances were most likely positive during the second period (ca. 1890-1940). The third period (ca. 1940-till present) was characterised by moderate melting rate of glaciers located on the Kodar and Baikalsky Ridges, in contrast to Peretolchin Glacier that demonstrated the highest rate of melting and changes in outlines during this period.