Abstract:Understanding paleo—and recent environmental changes and the dynamics of individual drivers of water availability is essential for water resources management in the Mongolian Altai. Here, we follow a holistic approach to uncover changes in glaciers, permafrost, lake levels and climate at the Tsengel Khairkhan massif. Our general approach to describe glacier and lake level changes is to combine traditional geomorphological field mapping with bathymetric measurements, satellite imagery interpretation, and GIS an… Show more
“…(Figure 1a, b). Glacial advances from the south‐western slopes of the Tsengel Khairkhan Mountains left prominent moraine lobes during the last glaciation which blocked the valley and formed the endorheic Khar Nuur basin (Figure 1b) (Walther et al, 2017). The bedrock of most parts of the catchment is composed of friable black clay shales, whereas only the morainal deposits in the western parts of the catchment consist of granite.…”
Lake sediments are valuable natural archives to reconstruct paleoclimate and paleoenvironmental changes which consist of inorganic and organic sediment compounds of allochthonous origin from the catchment and of autochthonous production in the lake. However, for robust paleo-reconstructions it is important to develop a better understanding about sedimentation processes, the origin of inorganic and organic sediment compounds and their distribution within the lake. In this context, modern process studies provide important insights, although environmental and anthropological changes can affect the spatial distribution of sediment compounds through time. Therefore, in this study the spatial distribution of grain size and geochemical proxies in 52 surface sediment samples from Lake Khar Nuur, a small high-altitude lake in the Mongolian Altai with a small and anthropogenically used hydrological catchment, is investigated. The results show a distinct sediment focussing in the two deep basins of the lake, which therefore act as accumulation zones. In those accumulation zones, total organic carbon (TOC), total nitrogen (N) and their isotopic composition (δ 13 C TOC , δ 15 N) as well as n-alkanes indicate that organic sediment compounds are a mixture of both allochthonous and autochthonous origin. While the recent catchment vegetation consists of grasses/herbs and the shrub Betula nana (L.) with distinct differences in their n-alkane homologue patterns, those differences are not reflected in the sediment surface samples which rather indicates that grass-derived n-alkanes become preferentially incorporated in the lake. Extensive anthropogenic activity such as grazing and housing in the southern part of the catchment causes soil erosion which is well reflected by high TOC, N and sulphur (S) contents and 15 N depleted δ 15 N values at the central southern shore, i.e. increased allochthonous sediment input by anthropogenically-induced soil erosion. Overall, the surface sediments of Lake Khar Nuur origin from allochthonous and autochthonous sources and are focussed in the accumulation zones of the lake, while their distribution is both environmentally and anthropogenically driven.
“…(Figure 1a, b). Glacial advances from the south‐western slopes of the Tsengel Khairkhan Mountains left prominent moraine lobes during the last glaciation which blocked the valley and formed the endorheic Khar Nuur basin (Figure 1b) (Walther et al, 2017). The bedrock of most parts of the catchment is composed of friable black clay shales, whereas only the morainal deposits in the western parts of the catchment consist of granite.…”
Lake sediments are valuable natural archives to reconstruct paleoclimate and paleoenvironmental changes which consist of inorganic and organic sediment compounds of allochthonous origin from the catchment and of autochthonous production in the lake. However, for robust paleo-reconstructions it is important to develop a better understanding about sedimentation processes, the origin of inorganic and organic sediment compounds and their distribution within the lake. In this context, modern process studies provide important insights, although environmental and anthropological changes can affect the spatial distribution of sediment compounds through time. Therefore, in this study the spatial distribution of grain size and geochemical proxies in 52 surface sediment samples from Lake Khar Nuur, a small high-altitude lake in the Mongolian Altai with a small and anthropogenically used hydrological catchment, is investigated. The results show a distinct sediment focussing in the two deep basins of the lake, which therefore act as accumulation zones. In those accumulation zones, total organic carbon (TOC), total nitrogen (N) and their isotopic composition (δ 13 C TOC , δ 15 N) as well as n-alkanes indicate that organic sediment compounds are a mixture of both allochthonous and autochthonous origin. While the recent catchment vegetation consists of grasses/herbs and the shrub Betula nana (L.) with distinct differences in their n-alkane homologue patterns, those differences are not reflected in the sediment surface samples which rather indicates that grass-derived n-alkanes become preferentially incorporated in the lake. Extensive anthropogenic activity such as grazing and housing in the southern part of the catchment causes soil erosion which is well reflected by high TOC, N and sulphur (S) contents and 15 N depleted δ 15 N values at the central southern shore, i.e. increased allochthonous sediment input by anthropogenically-induced soil erosion. Overall, the surface sediments of Lake Khar Nuur origin from allochthonous and autochthonous sources and are focussed in the accumulation zones of the lake, while their distribution is both environmentally and anthropogenically driven.
“…The spatial patterning of the present coverage suggests that south-facing margins were most significantly impacted by the ice loss, especially at lower elevations. Figure 2 Ice extent in Tsengel region from 1990 through 2016, using glacier outlines Khairkhan from the Global Land Ice Measurements from Space (GLIMS) database 51 , 52 , modified from Walther et al 53 Ice Patch Survey boxes represent areas identified with more permanent ice (2010–2020) where we conducted intensive surveys of the maximum melt extent in August 2019. Inset shows the location of the study area relative to the boundary of the Pleistocene glaciation.…”
Section: Resultsmentioning
confidence: 99%
“…Ice extent in Tsengel region from 1990 through 2016, using glacier outlines Khairkhan from the Global Land Ice Measurements from Space (GLIMS) database 51,52 , modified from Walther et al 53 Pedestrian and horseback survey. Our survey of five ice patches and one glacier margin revealed three localities bearing artifacts and ancient biological material, as well as one locality where faunal remains, with no direct evidence of a cultural origin, were recovered from periglacial pools frozen at the time of recovery (Supplementary Fig.…”
The transition from hunting to herding transformed the cold, arid steppes of Mongolia and Eastern Eurasia into a key social and economic center of the ancient world, but a fragmentary archaeological record limits our understanding of the subsistence base for early pastoral societies in this key region. Organic material preserved in high mountain ice provides rare snapshots into the use of alpine and high altitude zones, which played a central role in the emergence of East Asian pastoralism. Here, we present the results of the first archaeological survey of melting ice margins in the Altai Mountains of western Mongolia, revealing a near-continuous record of more than 3500 years of human activity. Osteology, radiocarbon dating, and collagen fingerprinting analysis of wooden projectiles, animal bone, and other artifacts indicate that big-game hunting and exploitation of alpine ice played a significant role during the emergence of mobile pastoralism in the Altai, and remained a core element of pastoral adaptation into the modern era. Extensive ice melting and loss of wildlife in the study area over recent decades, driven by a warming climate, poaching, and poorly regulated hunting, presents an urgent threat to the future viability of herding lifeways and the archaeological record of hunting in montane zones.
“…Potential exists in using more comprehensive metrics including the normalized difference in air and ground temperatures [60] and changes in volumetric water content [61]. The possibility for the derivation of these metrics is increasing as Mongolia continues to develop their borehole and climate monitoring networks [62,63].…”
Livestock production is a socioeconomic linchpin in Mongolia and is affected by large-scale livestock die-offs. Colloquially known as dzuds, these die-offs are driven by anomalous climatic events, including extreme cold temperatures, extended snow cover duration (SCD) and drought. As average temperatures across Mongolia have increased at roughly twice the global rate, we hypothesized that increasing cold season surface melt including soil freeze/thaw (FT), snowmelt, and icing events associated with regional warming have become increasingly important drivers of dzud events as they can reduce pasture productivity and inhibit access to grazing. Here, we use daily brightness temperature (T b ) observations to identify anomalous surface melt and icing events across Mongolia from 2003-2016 and their contribution to dzuds relative to other climatic drivers, including winter temperatures, SCD, and drought. We find a positive relationship between surface melt and icing events and livestock mortality during the fall in southern Mongolia and during the spring in the central and western regions. Further, anomalous seasonal surface melt and icing events explain 17-34% of the total variance in annual livestock mortality, with cold temperatures as the leading contributor of dzuds (20-37%). Summer drought showed the greatest explanatory power (43%) but overall had less statistically significant relationships relative to winter temperatures. Our results indicate that surface melt and icing events will become an increasingly important driver of dzuds as annual temperatures and livestock populations are projected to increase in Mongolia.
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