State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing, China.
College of Earth Sciences, University of Chinese Academy of Sciences, Beijing, China.
PLoS One. 2020 May 6;15(5):e0232803. doi: 10.1371/journal.pone.0232803. eCollection 2020.
The eastern Tibetan Plateau (TP) is a climatically sensitive area affected by the Indian Summer Monsoon (ISM). A new pollen record from a lacustrine sediment in Mao County shows that the study area was covered mainly by shrubs and herbs during the last deglaciation, indicating open and sparse forest grasslands. Hydrophilous herbs were mainly dominated by Cyperaceae, Poaceae, Myriophyllum, Polygonum and Typha, and they gradually increased from 18.7 to 16.8 ka, suggesting a transition to a more humid climate. This corresponds to climate cooling over the same period. From 16.8 to 14.6 ka, hydrophilous herbs continued to increase, coincident with a general ameliorating trend indicated by δ18O records from East Asia. Between 14.6 and 14.0 ka, the mean content of hydrophilous herbs reached peak in the sequence, corresponding to relatively high δ18O values during this period. From ~14.0 to 12.9 ka, the abundance of hydrophilous herbs decreased significantly. Over the same period, the Greenland ice core shows a decrease in δ18O and low-latitude cave stalagmites in China record an increase in δ18O. This implies that longitudinal temperature gradients increased and drove the southward retreat of the ISM, which in turn drove a continuous decrease in the abundance of hydrophilous herbs in the study area. From 12.9 to 11.6 ka, the mean content of hydrophilous herbs decreased to the lowest (8.3%) in the whole sequence, indicating a cold and dry climate in the study area. A positive shift in δ18O records during 11.6-10.6 ka was matched by a significant increase in the abundance of hydrophilous herbs in the study area, indicating a warm and humid climate trending. Hence, the ISM has had a significant impact on the climate of the eastern TP since the onset of deglaciation around ~16.8 ka.
青藏高原东部（TP）是一个受印度夏季风（ISM）影响的气候敏感区。毛县湖泊沉积物中的一个新花粉记录表明，在末次冰消期，研究区主要被灌木和草本植物覆盖，指示着开阔稀疏的森林草原。湿地草本植物主要以莎草科、禾本科、竹叶眼子菜、蓼属和香蒲属为主，从 18.7 到 16.8ka 逐渐增加，表明气候向更湿润的方向转变。这与同期的气候变冷相对应。从 16.8 到 14.6ka，湿地草本植物继续增加，与东亚δ18O 记录所指示的整体改善趋势一致。在 14.6 到 14.0ka 之间，草本植物的平均含量在序列中达到峰值，对应于这一时期相对较高的δ18O 值。从14.0 到 12.9ka，湿地草本植物的丰度显著下降。同期，格陵兰冰芯显示δ18O 值下降，中国低纬度洞穴石笋记录δ18O 值增加。这意味着经向温度梯度增加，并驱动 ISM 向南退缩，进而导致研究区湿地草本植物丰度持续减少。从 12.9 到 11.6ka，湿地草本植物的平均含量下降到整个序列中的最低值（8.3%），指示研究区气候寒冷干燥。11.6-10.6ka 期间δ18O 记录的正偏移与研究区湿地草本植物丰度的显著增加相匹配，指示着温暖湿润的气候趋势。因此，自16.8ka 左右冰消期开始以来，ISM 对青藏高原东部的气候产生了重大影响。
