Late Holocene environmental change: evidence from Lake Xiaolongwan, north east China and Lake Arachlei, south eastern Siberia

• Main Author: Panizzo, V.N.
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UCL (University College London) 2010
• Subjects: North Atlantic; Siberia
• Online Access: https://discovery.ucl.ac.uk/id/eprint/516143/1/516143.pdf; https://discovery.ucl.ac.uk/id/eprint/516143/

This project addresses the increasing need for high-resolution proxy studies of environmental change over the late Holocene from regions in northern Eurasia. The late Holocene has been identified as a key timeframe for investigating environmental change (e.g. PAGES Focus 2) due to the relatively small changes in boundary conditions. In particular, this project focuses on two sites; Lake Xiaolongwan, north east China, sensitive to changes in summer (EASM) and winter (EAWM) monsoonal intensity and Lake Arachlei, south east Siberia, sensitive to changes in Westerly transport and Siberian High intensity. This project provides a detailed high-resolution reconstruction of diatoms and bulk organic isotopes from cores collected at each of these sites. The c. 2000 year record from Lake Xiaolongwan, has an age model derived from varve counting, 210Pb and SCPs. Ecological interpretations of diatom changes suggests a long term trend towards decreased lake water level and increased lake productivity (after c. 1650 years BP). Superimposed upon the trend are significant periods of assemblage changes thought to represent intensified EAWM intensity, occuring between c. 1450-1350 and 600-400 years BP, which are coincident with evidence of north Atlantic ice raft debris (IRD) events. At Lake Arachlei, a similar trend of decreasing lake levels is also identified over the c. 3000 year record (based on a 14C and 210Pb age model). Significant assemblage changes are demonstrated between c. 3000-2800, 1450-1350 and 500-400 years BP, thought to indicate reduced Westerly transport to the region. These periods are coincident with Bond events 2, 1 and 0. This project demonstrates the role of teleconnections in the late Holocene, which may be responsible for environmental change. Nevertheless, the dramatic change identified in the Lake Xiaolongwan record after c. 1950 cannot be attributed to evidence of global warming in the region due to the demonstrated evidence of anthropogenic impacts (XRF and SCPs) in this otherwise perceived pristine ...