NOAA/WDS Paleoclimatology - 10Be Chronology of Khoton Nuur Glacial Landforms since the Last Glaciation, Mongolian Altai, Central Asia

Determining what caused the global Last Glaciation and last glacial termination, despite opposing orbital summer insolation signatures between the polar hemispheres, remains a puzzle of paleoclimatology. This problem can be addressed by comparing chronologies of glaciation from different latitudes and different climatic regimes in both hemispheres. Here, we present a 10Be surface-exposure chronology of glacial landforms constructed during and since the local Last Glaciation in the continental environment of interior Asia, in the high Mongolian Altai (49°N, 88°E). Four belts of lateral moraines document maximal phases of the former Khoton glacier at 35,400 ± 980 yrs ago; 23,430 ± 850 yrs ago; 20,780 ± 610 yrs ago; and 19,520 ± 550 yrs ago. Our chronology indicates that deglaciation from these maximal positions began as early as 18,810 ± 510 yrs ago, was well underway by 17,680 ± 510 yrs ago, and was nearly complete by 16,040 ± 490 yrs ago. Overall, our chronology shows that glaciation in western Mongolia coincided with the global Last Glacial Maximum (LGM), and that extensive recession from glacial-to-interglacial limits took place rapidly early in the last glacial termination, during Heinrich stadial 1. The transition from glacial to interglacial conditions led the demise of large Northern Hemisphere ice sheets and increase in radiative forcing agents by several millennia. We suggest that this rapid switch in the mode of glaciation implies the involvement of an additional climatic factor that could have produced locally rapid warming and deglaciation ~18,800 – 16,000 yrs ago.