Abrupt Freshening Since the Early Little Ice Age in Lake Sayram of Arid Central Asia Inferred From an Alkenone Isomer Proxy

Abstract

Hydroclimatic variations of arid central Asia (ACA) significantly impact regional ecosystems and human civilizations. Here we present a lake water salinity record of the last 3,000 years from Lake Sayram in the core area of ACA using a new alkenone isomer‐based RIK37 index. Our record shows an abrupt decrease in salinity by more than 5‰ since the “early” Little Ice Age (LIA) (about CE 1150), which can be attributed to the combined effect of regional wetting, cooling, and topographic features. Combined with other moisture records in the region, we find two periods of relatively wet conditions during CE 1150–1550 and 1850 to present, which may be linked to Arctic sea ice expansion due to natural variability and, from CE 1950, anthropogenically induced warming. The wet conditions during CE 1206–1260 may have favored the spread of the Mongol Empire across the entire core area of ACA.

Central Mongolian lake sediments reveal new insights on climate change and equestrian empires in the Eastern Steppes

“…Sustained humid conditions likely enabled the expansion of fertile grasslands and thus, increased ecosystem carrying capacity 14 , 17 , 61 — allowing to raise larger numbers of livestock and horses for both meat and dairy production 9 , 11 . Particularly in the dry and seasonal steppe environment, domestic livestock herds experience “economies of scale” — wherein smaller herds are more vulnerable to loss from disease, predation, or weather, and larger herds are more resilient 62 .…”

“…This likely favored the union of nomadic tribes under Genghis Khan and the formation of the Mongol Empire, which began during the early thirteenth century and reached its greatest spatial extent during the late 13th through the mid-fourteenth century (Fig. 4 i) 13 , 14 , 61 .…”

Fires, Vegetation, and Human—The History of Critical Transitions During the Last 1000 Years in Northeastern Mongolia

“…Climate cooling in this period could have enhanced permafrost aggradation, thus decreasing the permeability of local soils (Hahn et al, 2013). On the other hand, some evidence indicates an increase in humidity in Central Asia during the LIA (Chen et al, 2006;Dugerdil et al, 2021;Lan et al, 2018;Putnam et al, 2016;Yao et al, 2020). Enhanced surface runoff and restricted water infiltration to deeper layers of frozen soils (Hahn et al, 2013) together resulted in a high level of groundwater and thus low redox conditions in the KHN site, as revealed by high Fe/Mn values (Boyle, 2001) as well as the appearance of palustrine and open water plant sporomorphs such as marsh arrowgrass (Triglochin), Potamogeton-type pollen, and Ceratophyllum spine.…”

Climate Change and Equestrian Empires in the Eastern Steppes: New Insights from a High-resolution Lake Core in Central Mongolia

“…Sustained humid conditions likely enabled the expansion of fertile grasslands and thus, increased ecosystem carrying capacity 14,17,54 -allowing to raise larger numbers of livestock and horses for both meat and dairy production 9,11 . Particularly in the dry and seasonal steppe environment, domestic livestock herds experience "economies of scale" -wherein smaller herds are more vulnerable to loss from disease, predation, or weather, and larger herds are more resilient 55 .…”

“…This likely favored the union of nomadic tribes under Genghis Khan and the formation of the Mongol Empire, which began during the early 13th century and reached its greatest spatial extent during the late 13th through the mid-14th century (Fig. 3f) 13,14,54 .…”