Mid- to late Holocene cooling events in the Korean Peninsula and their possible impact on ancient societies

Abstract

We present a multiproxy record using pollen, magnetic susceptibility, carbon isotopic composition, carbon/nitrogen ratio, and particle size of mid- to late Holocene environmental changes based on a sediment core from the Pomaeho lagoon on the east coast of Korea. The records indicate that climate deteriorations around 6400 cal yr BP and 4000 cal yr BP caused rapid vegetation changes in the study area, which were presumably attributable to low sunspot activity and strong El Niño–like conditions, respectively. These two cooling events were likely modulated by different climate mechanisms, as El Niño–Southern Oscillation activity began to strengthen around 5000 cal yr BP. These events may have had a substantial impact on ancient societies in the study area. Combining our results with archaeological findings indicated that climate deterioration led to drastic declines in local populations around 6400 cal yr BP, 4400 cal yr BP, and 4000 cal yr BP. Because of its high population, coastal East Asia (e.g., eastern China, Japan, and Korea) is particularly vulnerable to potential cooling events in the future. Therefore, there is a strong need for detailed paleoclimate information in this region.

Holocene hydroclimate reconstruction based on pollen, XRF, and grain-size analysis and its implications for past societies of the Korean Peninsula

“…Among these periods, a sign of drying and/or cooling around 6.4-6.0 ka BP (Fig. 4b-e) is consistent with previous findings at Lake Pomaeho in the central Korean Peninsula (Constantine et al, 2019) (Fig. 1b).…”

“…6a and b). Together with our previous research (Constantine et al, 2019;Park et al, 2019), this robust synchronicity between Ti data and archaeological records contributes to accumulating evidence that past societies of the Korean Peninsula responded strongly and with great sensitivity to climate change.…”

“…4f), which is located directly on the path of the KC (Fig. 1a), which is an important contributor to EASM strength in coastal East Asia, where it is a major transport mechanism of heat and moisture from the WTP (Jian et al, 2000;Zhou et al, 2009;Lim and Fujiki, 2011;Hu et al, 2015;Park et al, 2016;Constantine et al, 2019;Lee et al, 2020). During ca.…”

“…6). Evidence of significant cooling and drying events around this period (Bond et al, 1997;Wang et al, 2005;Wanner et al, 2011;Bond et al, 2001) and their potential impacts on the shrinkage or unrest of past societies (DeMenocal, 2001) have been widely reported from various sites worldwide including Mesopotamia (Weiss et al, 1993;Carolin et al, 2019), India (Dixit et al, 2018;Dixit et al, 2014), China (An et al, 2005;Li et al, 2018;Xiao et al, 2018;Xu et al, 2019), Japan (Kajita et al, 2020;Kawahata et al, 2009), and Korea (Constantine et al, 2019;Park et al, 2019). In these periods, climate drying would have increased dietary stress by hindering successful hunting, gathering, millet cultivation and even livestock domestication (Roffet-Salque et al, 2018;Kawahata et al, 2009).…”

“…Therefore, to analyze socio-environmental relationships in a particular area accurately, a direct comparison of continuous, local, and high-resolution paleoclimate proxy data with human activity indicators is crucial. However, in the Korean Peninsula, this work remains in the nascent stage (Constantine et al, 2019;Park et al, 2019). The topic of climate-society relationships in Korea often depends on individual historical records of natural disasters, leading to assumptive storytelling about their potential impact on contemporary societal unrest (Cho, 2009).…”