Siberian Permafrost Thawing Accelerated at the Bølling/Allerød and Preboreal Warm Periods During the Last Deglaciation

Abstract

This study investigated a continuous sediment core, retrieved from the deepest part in Lake Hovsgol, northwestern Mongolia. Its surrounds are occupied by a continuous Siberian permafrost zone. Distinct geochemical and lithological features suggest that the watershed soil was moistened during the last deglaciation, associated with climate amelioration. Especially, the calcareous glacial clay layers (ca 13.7 and ca 11.0 cal. ka BP), with high sulfur content peaks and positive shifts of δ 34 S values, well correlate with the timing of meltwater pulses 1A and 1B, leading to rapid warming such as Bølling/Allerød and Preboreal Holocene, respectively. This finding allows our interpretation for the calcareous glacial clay layers produced by landslide-induced debris flow, which resulted from intensive water discharge from rapid thawing of permafrost during the abrupt warming periods. Our correlation with Lake Baikal records suggests that these permafrost thawings have accelerated over the area of the Selenga drainage basin (continental interior Eurasia).

A Chironomid Record of Early-Middle Holocene Environmental Evolution in the Darhad Basin, Northern Mongolia

“…The driving factor may be the rise in temperature caused by strong solar insolation since the early Holocene [ 72 , 73 , 74 ] ( Figure 6 d,e). The rapid melting of glaciers and permafrost in the Darhad Basin increased runoff into the lake [ 75 , 76 , 77 , 78 ], which resulted in the rapid lake area expansion and water level rise [ 79 , 80 ] ( Figure 6 f). Similarly, the Holocene climate records reconstructed by pollen from Lake Baikal show that warm and humid conditions began to appear around 9.0 cal kyr BP [ 81 ] ( Figure 6 g).…”