Long-term glacier melt fluctuations over the past 2500 yr in monsoonal High Asia revealed by radiocarbon-dated lacustrine pollen concentrates

• Published in: Geology
• Main Authors: Zhang, Ji-Feng, Xu, Baiqing, Turner, Falko, Zhou, Liping, Gao, Pan, Lu, Xinmiao, Nesje, Atle
• Other Authors: Zhang, JF (reprint author), Chinese Acad Sci, Inst Tibetan Plateau Res, Key Lab Tibetan Environm Changes & Land Surface P, Beijing 100101, Peoples R China., Chinese Acad Sci, Inst Tibetan Plateau Res, Key Lab Tibetan Environm Changes & Land Surface P, Beijing 100101, Peoples R China., Chinese Acad Sci, CAS Ctr Excellence Tibetan Plateau Earth Syst Sci, Beijing 100101, Peoples R China., Tech Univ Carolo Wilhelmina Braunschweig, Inst Geosyst & Bioindicat, D-38106 Braunschweig, Germany., Peking Univ, Dept Geog, Lab Earth Surface Proc, Beijing 100871, Peoples R China., Peking Univ, Ocean Res Inst, Beijing 100871, Peoples R China., Univ Bergen, Dept Earth Sci, Allegt 41, N-5007 Bergen, Norway.
• Format: Journal/Newspaper
• Language: English
• Published: GEOLOGY 2017
• Subjects: TIBETAN PLATEAU; LATE HOLOCENE; TEMPERATURE-CHANGES; ICE CAP; RECORD; CHINA; VARIABILITY; GLACIATION; NORWAY; KA; Norway; glacier; Ice cap
• Online Access: https://hdl.handle.net/20.500.11897/474427; https://doi.org/10.1130/G38690.1

Long-term records of glacier mass changes are important for improving our understanding of glacier dynamics and for predicting the response of glaciers to future climate change. In contrast to moraine sequences that only record isolated stages of glacier status, proglacial lake sediments may record long-term continuous glacier activities. The melt of old glacier ice releases old pollen that may affect the radiocarbon ages of pollen in proglacial lake sediments. We define the offset between the calibrated pollen C-14 ages and the sediment depositional age as the "old pollen effect" (OPE). In small catchments dominated by glaciers, the OPE may record variations in glacier melt intensity and extent, even though complex processes (e.g., modern pollen flux to a glacier or a proglacial lake, glacier flow velocities) may also impact the OPE. Using the sediments of a small proglacial lake on the southern Tibetan Plateau, we found that over the past 2.5 k.y., a weakened OPE occurred during three historical cool periods that coincided with regional glacier advances defined by moraine ages. Thus, we interpret the OPE as a new indicator of glacier melt intensity and its fluctuations. Our reconstructed glacier variability agrees well with glacier fluctuations in the European Alps and the global average temperature record, suggesting that hemispheric-scale temperature variations and/or mid-latitude Westerlies may have controlled the late Holocene glacier variability in monsoonal High Asia. We also show that the 20th century glacier melt intensity has exceeded that of two historical warm periods and is unprecedented over the past 2.5 k.y. This implies that current anthropogenic warming poses a serious threat to the survival of glaciers in monsoonal High Asia. National Science Foundation of China [41501086]; International Partnership Program of the Chinese Academy of Sciences [131C11KYSB20160061] SCI(E) ARTICLE 4 359-362 45