Sedimentological data and hydrogen isotopic measurements of leaf wax long-chain n-alkanes (δD wax ) from an alpine lake sediment archive on the southeastern Tibetan Plateau (Paru Co) provide a Holocene perspective of Indian summer monsoon (ISM) activity. The sedimentological data reflect variations in lake level and erosion related to local ISM rainfall over the Paru Co catchment, whereas δD wax reflects integrated, synoptic-scale ISM dynamics. Our results indicate that maximum ISM rainfall occurred between 10.1 and ~5.2ka, during which time there were five century-scale high and low lake stands. After 5.2 ka, the ISM trended toward drier conditions to the present, with the exception of a pluvial event centered at 0.9 ka. The Paru Co results share similarities with paleoclimate records from across the Tibetan Plateau, suggesting millennial-scale ISM dynamics were expressed coherently. These millennial variations largely track gradual decreases in orbital insolation, the southward migration of the Intertropical Convergence Zone (ITCZ), decreasing zonal Pacific sea surface temperature (SST) gradients and cooling surface air temperatures on the Tibetan Plateau. Centennial ISM and lake-level variability at Paru Co closely track reconstructed surface air temperatures on the Tibetan Plateau, but may also reflect Indian Ocean Dipole events, particularly during the early Holocene when ENSO variability was attenuated. Variations in the latitude of the ITCZ during the early and late Holocene also appear to have exerted an influence on centennial ISM rainfall.
Bibliographical noteFunding Information:
Funding for this research was provided by the United States National Science Foundation ( EAR-1023547 ) and the Chinese National Natural Science Foundation of China (Award 41150110153 ). Special thanks to Nima for his invaluable assistance with fieldwork and to Angela Robertson for her assistance with the perpetration and measurement of the grain size samples. We also thank John Southon at the University of California, Irvine, Keck Carbon Cycle AMS facility for his assistance with the radiocarbon dating and the Limnological Research Center at University of Minnesota. B.A.S acknowledges support from the US NSF AGS-PRF ( AGS-1137750 ). We would also like to thank the three anonymous reviewers and Dr. Jean Lynch-Stieglitz for their comments on this work.
- Global change
- Grain size
- Lake levels
- Leaf wax hydrogen isotopes