Consistent long‐term Holocene warming trend at different elevations in the Altai Mountains in arid central Asia

Abstract

Recent results indicate contrasting Holocene moisture histories at different elevations in arid central Asia (ACA). However, relatively little is known about Holocene temperature changes at different elevations. Here we report an independently dated peat brGDGTs-based MBT' 5ME record from the Narenxia peatland (NRX) in the southern Altai Mountains. The record suggests a long-term warming trend since~7.7 cal. kyr BP, with a warmer stage during~7-5.5 cal. kyr BP, a cold stage during~5.5-4 cal. kyr BP, and a warming trend over the last~4 kyr. The longterm warming trend indicated by the NRX MBT' 5ME record is largely consistent with Holocene temperature records from nearby sites covering an altitudinal range of~1700-4100 m above sea level. This consistent long-term warming trend at different elevations differs from the long-term Holocene drying/wetting trends at high/low elevations of the Altai Mountains. We propose that the warming trend and consequent permafrost thawing at high elevations could have resulted in increased meltwater runoff, which would have contributed to the long-term wetting trend at low elevations. Our findings potentially provide an improved understanding of regional climate change and associated water resource availability, with implications for their possible future status.

Climate reconstructions based on GDGT and pollen surface datasets from Mongolia and Baikal area: calibrations and applicability to extremely cold–dry environments over the Late Holocene

“…1; Bezrukova et al, 2005;Binney, 2017) are compared to the Xiangride section (XRD) used for the brGDGT sequence from Sun et al (2019), sampled in the Chinese Qaidam Basin and the NRX peat bog (Chinese Altai, Fig. 2; Rao et al, 2020). These two cores have recorded the paleoenvironmental changes of the Late Holocene period.…”

“…2; Sun et al, 2019) and the NRX bog (Figs. 1a and 2; Rao et al, 2020). Fractional abundances of (a) isoGDGTs and (b) brGDGTs for moss polsters (green), soil surface samples (orange) mud from temporary dry ponds (blue) and the full sequence of the Lake MMNT5C12 as paleo-brGDGTs comparison (grey).…”

“…S3 in the Supplement. Even if the impact of salinity on sporopollenin is not well understood, salt properties may affect pollen conservation in soils (Reddy and Goss, 1971;Gul and Ahmad, 2006).…”

“…To test the reliability of our local calibrations, the pollen transfer function and the brGDGT mr models have been applied on four paleosequences. Because there is still no available core analyzed for both pollen and brGDGTs either in ACA area or in the MP, the Dulikha bog (pollen, Baikal; Bezrukova et al, 2005;Binney, 2017), the D3L6 lake (pollen, Altai; Unkelbach et al, 2019), the NRX bog (Altai, GDGTs; Rao et al, 2020) and the XRD section (Qaidan, GDGTs; Sun et al, 2019) are used. The actual values of the climatic parameters are first compared to the top-core reconstructed climatic parameters (Fig.…”

“…ACA climate reconstruction for the 5000 yr cal BP. (a) Climate-pollen inferred for the Dulikha peat bog(Bezrukova et al, 2005;Binney, 2017) and (b) Lake D3L6 (Unkelbach et al, 2019) comparing two transfer function methods (WAPLS and MAT) and the four databases (EAPDB, COSTDB, MDB and NMSDB); (c) climate-brGDGT inferred from the XRD section(Sun et al, 2019) and (d) the NRX peat bog(Rao et al, 2020) comparing local (NMSDB) and global calibrations(De Jonge et al, 2014a;Naafs et al, 2017a, b). The climate periods correspond to Little Ice Age (LIA), Warm Medieval Period (WMP), Dark Ages Cold Period (DACP), Roman Warm Period (RWP), 3.5 and 4.2 ka event according toZhang et al (2008),Aichner et al (2015) andSun et al (2019).…”