Millennial Indian Monsoon variability and forcing during the Holocene as revealed by the Qinghai Lake, Yunnan Province Record

Harrison, Cairns (2019) Millennial Indian Monsoon variability and forcing during the Holocene as revealed by the Qinghai Lake, Yunnan Province Record. MSc(R) thesis, University of Glasgow.

Abstract

The Indian Summer Monsoon (ISM) is an incredibly influential climate system, with many developing nations and over 1 billion people reliant upon favourable monsoon conditions. A suite of organic paleoclimate proxy biomarkers was extracted from sediment core samples retrieved from Qinghai Lake, Yunnan Province, southwest China in order to reconstruct various climate parameters at high-resolution in the region throughout the Holocene. The main aim of the project is to investigate changes caused by the ISM. The upper 145cm of the core were analysed covering an age range of 8877 cal yr BP (calibrated years before present) to -16 cal yr BP (cal yr BP denotes calibrated years before present hereafter). The results indicate several distinct climatic regimes, often separated by abrupt changes in climate. From 8877 cal yr BP to 6895 cal yr BP multiple proxies imply a prolonged period of warm, wet climate and thus an intense ISM system during this period which likely represents the Holocene Climatic Optimum (HCO). Between 6895 cal yr BP and 3240 cal yr BP the climate becomes much more chaotic with several distinct drops and spikes in temperature and changes in precipitation illustrated by the average chain length (ACL) and short to long-chain acid ratio. Overall, during this period the climate was more arid with a weaker monsoon in the Yunnan province than during the HCO, but there was a high degree of variation in monsoon intensity indicated by almost all proxies with rapid changes in precipitation. ACL values sharply spiked to high values similar to the HCO period from 3540 cal yr BP to 3240 cal yr BP. Following on from 3240 cal yr BP to 1130 cal yr BP, a high value ACL plateau along with PWax/PAq, and acid ratio data indicates a warm, wet period and the return of strong monsoon intensity during the Roman Warm Period (RWP). A brief cool, dry period with a weaker monsoon followed by a rapid rise in temperature and monsoon intensity between 1133 cal yr BP-755 cal yr BP likely represents the Medieval Warm Period (MWP). Over the final 755 cal yr BP to -16 cal yr BP period of this record the ACL, carbon preference index (CPI), acid ratio and PWax/PAq record suggests progressively cooler and increasingly intense monsoon conditions during the Little Ice Age (LIA) towards the present in the Qinghai Lake region.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Subjects: Q Science > QE Geology
• Colleges/Schools: College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
• Supervisor's Name: Toney, Professor Jaime
• Date of Award: 2019
• Depositing User: Mr Cairns Harrison
• Unique ID: glathesis:2019-73039
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 07 Jun 2019 13:03
• Last Modified: 05 Mar 2020 22:11
• Thesis DOI: 10.5525/gla.thesis.73039
• URI: https://theses.gla.ac.uk/id/eprint/73039