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

Abstract

Late Holocene Indian summer monsoon variability revealed from a 3,300-year-long 1 lake sediment record from Nir'pa Co, southeastern years. Constrained by modern calibration elevated silt and lithics and low sand and clay 24 between 3.3-2.4 ka and 1.3 ka to the present indicate two pluvial phases with lake levels 25 near their current overflow elevation. Between 2.4-1.3 ka, a sharp increase in sand and 26 corresponding decrease in lithics and silt suggest drier conditions and lower lake levels at 27Nir'pa Co. Hydroclimate expressions in the sedimentological proxies during the 28Medieval Climate Anomaly (MCA) and Little Ice Age (LIA) are not statistically 29 significant, suggesting that these events were minor compared to the millennial scale 30 variability on which they were superimposed. However, decreasing sand and increasing 31 lithics and silt during the MCA between 950-800 cal yr B.P. 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. Despite an 54 improved understanding of long-term Holocene ISM trends and the likely driving 55 mechanisms, higher frequency ISM variations have been more difficult to characterize 56 because there are comparatively few high-resolution records from the Third Pole (Chen et 57 al., 2015). The late Holocene is under represented by high-resolution paleoclimate 58 records in part because mean state aridity resulted in decreased resolution (e.g., Bird et 59 al., 2014) or depositional hiatuses in many ISM archives (Berkelhammer et al., 2012; 60 Morrill et al., 2006;Cai et al., 2012). 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 ...

Fire, vegetation, and Holocene climate in a southeastern Tibetan lake: a multi-biomarker reconstruction from Paru Co

“…The ISM weakened after ∼ 5.2 cal kyr BP, with the exception of a pluvial event centred at 0.9 cal kyr BP. Nir'pa Co, a small lake located near Paru Co, suggests a wet period between 3.3 and 2.4 cal kyr and drier conditions from 2.4 to 1.3 cal kyr, due to lower silt and lithic content, coincident with elevated sand and clay content and lower lake levels (Bird et al, 2017).…”

“…time (Yan and Wünnemann, 2014). Numerous recent studies demonstrate climatic variations throughout China and surrounding areas during the Holocene using lacustrine sedimentary records (Bird et al, 2017;Dietze et al, 2013;Liu et al, 2009;Opitz et al, 2012;Saini et al, 2017;Yanhong et al, 2006). The paleoclimate proxies used in these studies -including carbonate percentages, mineralogy, grain-size distribution, elemental geochemistry, stable isotope composition, leaf wax long-chain n-alkanes, aquatic diatoms, and terrestrial pollen -collectively record changes in hydroclimate and other environmental processes such as vegetation growth, detrital influx, and volcanic eruptions.…”

Chronology of a lacustrine core from Lake Linggo Co using a combination ofOSL,14C and210Pb dating: implications for the dating of lacustrine sediments from the Tibetan Plateau

“…Many age-depth models for lacustrine sediments on the TP have been based principally on 14 C ages (e.g. Gasse et al 1991;Morinaga et al 1993;Fontes et al 1996;Ji et al 2005;Herzschuh et al 2006;Morrill et al 2006;Wu et al 2006;Zhu et al 2009Zhu et al , 2015An et al 2012;Peng et al 2013;Ma et al 2014;Miehe et al 2014;Hu et al 2015a;Bird et al 2016;Henkel et al 2016). Due to the lack of suitable charcoal for dating within the sediment, plant remains and/or the bulk organic materials within lacustrine sediments were used for 14 C dating in most of these studies.…”

Fire, vegetation and Holocene climate in the south-eastern Tibetan Plateau: a multi-biomarker reconstruction from Paru Co

“…The TOM only slightly varied displaying a modestly increasing trend across the Holocene. The BSi signal reflects changes in the ISM, with warmer and wetter climate between 11 to 5 cal ky BP followed by cooler and drier conditions (Bird et al, 2014(Bird et al, , 2017 Throughout the Holocene, the obtained data for ∑PAHs and ∑MAs do not correlate (r = -0.06, p-value 0.665). However, ∑PAHs and ∑MAs positively correlate during the early Holocene (10.9 -8.7 cal ky BP), with r = 0.51 (p-value 0.029), while in the following period (8.7 -1.3 cal ky BP) a slight, but not significant, negative correlation is observed, with r = -0.26 (pvalue 0.08).…”

“…The ISM weakened after ~ 5.2 cal ky BP, with the exception of a pluvial event centred at 0.9 cal ky BP. Nir'pa Co, a small lake located near Paru Co, suggests a wet period between 3.3 and 2.4 cal ky and drier conditions from 2.4 to 1.3 cal ky, due to lower silt and lithic content, coincident with elevated sand and clay content and lower lake levels (Bird et al, 2017). Clim.…”