A Tibetan lake sediment record of Holocene Indian summer monsoon variability

Late-Holocene Indian summer monsoon variability revealed from a 3300-year-long lake sediment record from Nir’pa Co, southeastern Tibet

“…Tibetan Plateau surface air temperatures (Bird et al, 2014). At Paru Co, an alpine lake in 75 the monsoon dominated southeastern Tibetan Plateau, Bird et al (2014) noted that low 76 lake stands and high hydrogen isotopic compositions of sedimentary leaf waxes (δD wax ) 77 coincided with warmer Indo-Pacific SST (Koutavas et al, 2006;Stott et al, 2004), cooler 78 eastern equatorial Pacific SST (Marchitto et al, 2010) and elevated surface air 79 temperatures on the central Tibetan Plateau (Herzschuh et al, 2006).…”

“…The paucity of climate records detailing ISM 61 variability during the last few millennia limits our understanding of monsoon dynamics 62 during a time when climatic boundary conditions were generally similar to the present, 63 but perturbations in radiative and other forcings, including ocean-atmosphere processes, 64 produced widely recognized climatic events including: the Medieval Climate Anomaly 65 (MCA; 950-1250 AD) and Little Ice Age (LIA; 1450-1900 AD) (Mann et al, 2009). 66Paleoclimate records from the Third Pole that span at least part of the late 67Holocene suggest that within this period of general aridity there were regional scale 68Bird et al (2016) Page 4 of 39 fluctuations in ISM precipitation, lake levels and temperature (Bird et al, 2014; 69 Herzschuh et al, 2006;Mischke and Zhang, 2010). Similar variability observed on longer 70 timescales in Holocene-length paleoclimate records suggest that sub-orbital climate 71 changes may be influenced by a variety of direct and indirect factors, including solar 72 variability (Cai et al, 2012), Atlantic and Indo-Pacific ocean-atmosphere teleconnections 73 (Chen et al, 2015;Bird et al, 2014;Hong et al, 2003;Goswami et al, 2006), and 74…”

“…2a). This valley is part of a larger plateau that contains numerous glacial 118 features, such as moraines and glacial lakes, including Paru Co (Bird et al, 2014). The 119 local bedrock is geologically homogeneous, consisting of Pleistocene age andesite 120 (Choubert et al, 1983).…”

“…may suggest briefly wetter 32 conditions while increasing sand and reduced lithics and silt from 500-200 cal yr B.P. an area referred to as the Third Pole Environment (Qiu, 2008), show that the Indian 47 summer monsoon (ISM) reached a maximum during the early and middle Holocene 48 between 10 and approximately 6 ka when boreal summer insolation peaked and strong 49 tropical Pacific sea surface temperature (SST) gradients resembled a La Niña-like mean 50 state (Koutavas et al, 2006;He et al, 2004;Bird et al, 2014;Cai et al, 2012; Yanhong 51 et al, 2006;Marchitto et al, 2010;Morrill et al, 2003). The late Holocene, in contrast, 52 has been characterized by increasing aridity as summer insolation waned and an 53 increasingly El Niño-like mean state developed in the tropical Pacific.…”

“…Bird et al (2016) Page 4 of 39 fluctuations in ISM precipitation, lake levels and temperature (Bird et al, 2014; 69 Herzschuh et al, 2006;Mischke and Zhang, 2010). Similar variability observed on longer 70 timescales in Holocene-length paleoclimate records suggest that sub-orbital climate 71 changes may be influenced by a variety of direct and indirect factors, including solar 72 variability (Cai et al, 2012), Atlantic and Indo-Pacific ocean-atmosphere teleconnections 73 (Chen et al, 2015;Bird et al, 2014;Hong et al, 2003;Goswami et al, 2006), and 74…”