Holocene evolution of the Indian Summer Monsoon inferred from a lacustrine record of Lake Wuxu, south‐east Tibetan Plateau

Abstract

A continuous sediment record since 12.3 cal ka bp from Lake Wuxu (south‐eastern Tibetan Plateau) was investigated in terms of the Holocene evolution of the Indian Summer Monsoon. The molar C/N ratio and stable C isotope were used to identify the source of the organic matter as well as climate conditions. The evolution of Lake Wuxu was summarized wihtin two periods. During the first period (early to mid‐Holocene), the lake received increased fluvially transported materials, reflecting variation in the summer monsoon with solar insolation. The lake level declined and water residence time increased because of reduced river discharge during the second period (late Holocene) corresponding to a weakening of the summer monsoon. The organic material revealed a major contribution from lake primary productivity, which showed identical patterns with a high‐resolution isotope record from Dongge Cave, as well as total solar irradiance. Our record from Lake Wuxu indicates that the Holocene evolution of the Indian Summer Monsoon has been driven by the solar forcing at decadal/centennial to millennial time scales. Furthermore, an abrupt decline in the monsoon was detected at around 4.0 cal ka bp, which is probably caused by an increased frequency of EI Nino‐Southern Oscillation events. Copyright © 2019 John Wiley & Sons, Ltd.

Current practices in building and reporting age-depth models

“…The popularity of Bayesian techniques appears to be increasing. Yue Wang et al (2019) document a fairly consistent increase in citations of OxCal (Bronk Ramsey, 2008) and Bacon (Blaauw and Christen, 2011), although in many cases OxCal is used solely for 14 C age calibration and not model building. Half of the models in our literature sample relied on a Bayesian approach, with most of these built using Bacon (34%), rather than OxCal (14%) or Bchron (6%).…”

“…Although Bayesian techniques use a different approach in the construction of age models, the ‘best-fit’ model can resemble simple linear interpolation e.g., when the mean age-depth model goes through each calibrated age range with changes in accumulation rate at dated depths. Resemblance to linear interpolation occurred in half (48%) of the Bacon models we examined (e.g., Yongbo Wang et al, 2019; McCulloch et al, 2019) and most if not all of the OxCal (e.g., Frodlová et al, 2018) and Bchron (e.g., Schiferl et al, 2018) models. Trachsel and Telford (2017) observed that “ although Bayesian age-depth modelling routines simulate changing accumulation rates, the mean accumulation rate (that is mostly used by scientists) is fairly constant between two dated levels, and therefore, the age-depth model is a straight line between two dated levels .” Similarity to linear interpolation is not altogether surprising, especially for Bacon and Bchron , as they are based in part on modelling piece-wise linear accumulations.…”

“…Resemblance to linear interpolation occurred in half (48%) of the Bacon models we examined (e.g., Yongbo Wang et al, 2019;McCulloch et al, 2019) and most if not all of the OxCal (e.g., Frodlová et al, 2018) and Bchron (e.g., Schiferl et al, 2018) models. Trachsel and Telford (2017) observed that "although Bayesian age-depth modelling routines simulate changing accumulation rates, the mean accumulation rate (that is mostly used by scientists) is fairly constant between two dated levels, and therefore, the age-depth model is a straight line between two dated levels."…”

Subannual-to-biannual-resolved travertine record of Asian Summer Monsoon dynamics in the early Holocene at the eastern margin of Tibetan Plateau

“…Moreover, the TP is one of the most sensitive areas to respond to global climate change (Liu and Chen, 2000). Therefore, the TP is an ideal site for studying the dynamics of the ASM (Zhou et al, 2010;Zhao et al, 2011;Cai et al, 2012;Bird et al, 2014;Zeng et al, 2017;Wang et al, 2019).…”

Indian summer monsoon variability over last 2000 years inferred from sediment magnetic characteristics in Lugu Lake, southwest China

“…These Lugu Lake is located on the southeast edge of the Qinghai-Tibet Plateau in Southwest China. The lakes in this area are tectonic lakes with fragile ecosystems, and can respond to environmental changes on scales from decades to millions of years (Chen et al, 2014;Wang et al, 2019). Magnetic measurement is a rapid, intensive, and non-destructive method to characterize high-resolution mineralogical changes, and is widely used in marine sequence comparison, paleoclimate, and provenance research (Peters et al, 2010;Chang et al, 2016;Wang et al, 2018aWang et al, , 2018b on lacustrine (Hu et al, 2015;Xu et al, 2020) and aeolian sediments (Gao et al, 2018).…”