Holocene precipitation and temperature variations in the East Asian monsoonal margin from pollen data from Hulun Lake in northeastern Inner Mongolia, China

Quantitative palaeoclimatic reconstruction with the weighted averaging partial least squares method was applied to the pollen profile from Hulun Lake in northeastern Inner Mongolia. The data provide a detailed history of variations in precipitation and temperature over the northeastern margin of the East Asian summer monsoon during the Holocene. A warm and dry climate prevailed over the lake region until c. 8000 cal. BP. During the period c. 8000-4400 cal. BP, precipitation increased markedly and temperature gradually declined. The interval between c. 4400 and 3350 cal. BP was marked by extremely dry and relatively cold conditions. Precipitation recovered from c. 3350 to 1000 cal. BP, with temperatures rising c. 3350-2050 cal. BP and dropping c. 2050-1000 cal. BP. During the last 500 years, the climate of the lake region displayed a general trend of warming and wetting. While Holocene temperature variations in the mid-high latitude monsoonal margin were controlled by changes in summer solar radiation in the Northern Hemisphere, they could also be related to the strength of the East Asian summer monsoon. The lack of precipitation during the early Holocene could be attributed to the weakened summer monsoon resulting from the existence of remnant ice sheets in the Northern Hemisphere. Changes in the monsoonal precipitation during the middle to late Holocene would have been associated with the ocean-atmosphere interacting processes occurring in the western tropical Pacific.