A Continuous Record of Indian Summer Monsoon Variability through the Holocene from Lake Sediments in Yunnan, China

Abstract:

Continuous terrestrial archives of the Indian Summer Monsoon through the Holocene are lacking, yet critical to providing a long-term perspective of hydroclimate variability. Here we present an 8,000 year sediment record from Xing Yun Lake in Yunnan, China that provides a semi-quantitative estimate of lake level change using stable isotopes of authigenic calcite as well as within-lake productivity using stable isotopes of organic matter. Substantial drops in lake level occur at 6,600 years BP, consistent with previous studies of a weaker monsoon system in the mid-Holocene due to declining summer insolation. Lake levels stabilize at 4,700 years BP and remain steady due to the topography surrounding the lake. From 5,600 to 5,100 and from 4,600 to 4,000 years BP, primary productivity decreases and is coincident with significant regional aridity as well as cooler Western Tropical Pacific sea surface temperatures. Variability in the stable isotopes of both calcite and organic matter after 1,500 years BP is primarily controlled by human activities. This study shows broad agreement with previous work on the Tibetan Plateau and provides one of the first continuous records of lake hydrologic balance from a crucial region affected by the Indian Summer Monsoon.