Indian Ocean Summer Monsoon (IOSM)-dynamics within the past 4聽ka recorded in the sediments of Lake Nam Co, central Tibetan Plateau (China)

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• 作者：Thomas Kasper^a ; ^{Thomas.Kasper.1@uni-jena.de} ; Torsten Haberzettl^a ; Stefan Doberschü ; tz^a ; Gerhard Daut^a ; Junbo Wang^b ; Liping Zhu^b ; Norbert Nowaczyk^c ; Roland Mä ; usbacher^a
• 关键词：Tibetan Plateau ; Monsoon ; Lake level variation ; Lake Nam Co ; Lake sediment ; Magnetostratigraphy
• 刊名：Quaternary Science Reviews
• 出版年：2012
• 期刊代码：78_02773791
• 类别：ear
• 出版时间：16 April, 2012
• 卷：39
• 期：Complete
• 页码：73-85
• 文件大小：1443 K

摘要

In September 2008 several cores (68聽cm-115聽cm length) (water depth: 93聽m) were retrieved from Lake Nam Co (southern-central Tibetan Plateau; 4718聽m a.s.l.). This study focuses on the interpretation of high-resolution (partly 0.2聽cm) data from three gravity cores and the upper part of a 10.4聽m long piston core, i.e., the past 4000聽cal BP in terms of lake level changes, hydrological variations in the catchment area and consequently variations in monsoon strength. A wide spectrum of sedimentological, geochemical and mineralogical investigations was carried out. Results are presented for XRF core-scans, grain size distribution, XRD-measurements and SEM-image analyses. These data are complemented by an age-depth model using ²¹⁰Pb and ¹³⁷Cs analyses as well as eleven AMS-¹⁴C-ages. This model is supported by excellent agreement between secular variations determined on one of the gravity cores to geomagnetic field models. This is a significant improvement of the chronology as most catchments of lacustrine systems on the Tibetan Plateau contain carbonates resulting in an unknown reservoir effect for radiocarbon dates. The good correlation of our record to the geomagnetic field models confirms our age-depth model and indicates only insignificant changes in the reservoir effect throughout the last 4聽ka.

High (summer-) monsoonal activity, i.e. moist environmental conditions, was detected in our record between approximately 4000 and 1950聽cal BP as well as between 1480 and 1200聽cal BP. Accordingly, lower monsoon activity prevails in periods between the two intervals and thereafter. This pattern shows a good correlation to the variability of the Indian Ocean Summer Monsoon (IOSM) as recorded in a peat bog 鈭?000聽km in NE direction from Lake Nam Co. This is the first time that such a supra regional homogenous monsoon activity is shown on the Tibetan Plateau and beyond. Finally our data show a significant lake level rise after the Little Ice Age (LIA) in Lake Nam Co which is suggested to be linked to glacier melting in consequence of rising temperatures occurring on the whole Tibetan Plateau during this time.