Science China Press
March 21, 2014
Chronologies of glacial advances during the last glacial period are not contemporaneous throughout the Tibetan Plateau. Professor YI Chaolu and his research group from the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, dated glacial boulders on moraines from the last glacial period in the Nyainqentanglha Mountains, Tibet. They suggested that glacial advances that occurred during a relatively warm period (MIS 3) between two cold stages of the last glacial episode in the Nyainqentanglha may correlate with millennial-scale climate change (Heinrich) events. Their work, entitled “10Be dating of boulders on moraines from the last glacial period in the Nyainqentanglha mountains, Tibet”, was published in SCIENCE CHINA Earth Sciences. 2014, Vol 45(2).
Glacial advances during MIS 3 (59 – 29 ka) on the Tibetan Plateau were previously attributed to the Asian monsoon, and thought to be a local last glacial maximum (LGM) in many regions. However, these studies were focused on monsoon-influenced regions of the Plateau. Glacial chronologies during MIS 3 differ throughout the Tibetan Plateau. The Nyainqentanglha range is in a transition zone at the margin of the present-day Asian monsoon: the area to the south is strongly influenced by the monsoon, that to the north is only slightly affected. Comparisons of glacial chronologies during MIS 3 on the south and north flanks of the range facilitate investigation of the regional synchronies and asynchronies, potentially relating to past climate changes.
During the last glacial episode, glaciers behaved similarly on both the northwest and southeast slopes of the Nyainqentanglha. At least two advances occurred, with a local last glacial maximum (LLGM) during MIS3, and a more limited glacial advance during the global LGM. Glacial advances on both slopes of the Nyainqentanglha are synchronous, within limits of uncertainty, but are not synchronous with those of the Northern Hemisphere ice sheet.
The oldest apparent exposure ages in three valleys show that glacial advances occurred at 39.9±3.7 ka, 45.3±4.2 ka, and 58.7±5.3 ka, roughly coincident with Heinrich events H4, H5, and H6 (37, 45, and 60 ka, respectively). The MIS3 glacial advances may not be strictly synchronous throughout the Nyainqentanglha and may be influenced both by these millennial-scale climate (D-O) oscillations and by increased precipitation associated with the southwest monsoon.
