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

Abstract

The dynamics of the East Asian Summer Monsoon (EASM) and their link to past societies during the Holocene are topics of growing interest. In this study, we present results of pollen, geochemistry, and grain-size analyses from the STP18-03 core sampled from Miryang in the Korean Peninsula, which spans ca. 8.3–2.3 ka BP. In-phase relationships of these proxies revealed an imprint of the Holocene Climate Optimum (HCO) during the early to mid-Holocene and subsequent drying toward the late-Holocene in accordance with decreasing solar insolation. At centennial timescales, our study indicates drier climate during ca. 7.5–7.1, 6.4–6.0, and 4.8–3.6 ka BP. Notably, our finding for ca. 6.4–6.0 ka BP contributes further evidence of a drying event in the Korean Peninsula during this period. We suggest that the Pacific Ocean played a role in the underlying mechanism of hydroclimate change in the region. A strong Kuroshio Current (KC) and long-term El Niño–Southern Oscillation (ENSO)-like variability in the Western Tropical Pacific (WTP) were closely linked to the influence of the EASM over the Korean Peninsula. In particular, dry phases during ca. 4.8–3.6 and 2.8–2.3 ka BP, which were synchronous with a more active ENSO, closely corresponded to lower population levels indicated by a summed probability distribution (SPD) of archaeological records previously assembled in the Korean Peninsula. This finding implies that past human societies of Korea were highly vulnerable to climate deterioration caused by precipitation deficits.

Mid-to-late Holocene climate variability in coastal East Asia and its impact on ancient Korean societies

“…The results of previous pollen studies in the Korean peninsula have suggested that the climate was comparatively dry during periods when WTP SSTs cooled because of long-term El Niño-Southern Oscillation-type variations 2 , 19 – 22 . The frequency of El Niño events may have increased, leading to reduced WTP SSTs and a smaller amount of atmospheric water vapor above the oceanic source region where the East Asian summer monsoon originates.…”

Hydroclimate change and its controlling factors during the middle to late Holocene and possible 3.7-ka climatic shift over East Asia

“…Human activity as a generator of flooding, or at least as an enhancer of flood events, during the middle to late Holocene needs to be considered. Recent studies have tested the possible relationship between population and climate change during the early to late Holocene (Oh et al, 2017; Park et al, 2021). Based on the comparison between pollen analyses from Miryang area in Korea and summed probability distributions of radiocarbon dates from archeological sites in Korea as a proxy for change in population levels, Park et al (2021) suggested that dry periods correspond to lower population levels during the early to late Holocene and that human societies were vulnerable to climate changes.…”

“…Recent studies have tested the possible relationship between population and climate change during the early to late Holocene (Oh et al, 2017; Park et al, 2021). Based on the comparison between pollen analyses from Miryang area in Korea and summed probability distributions of radiocarbon dates from archeological sites in Korea as a proxy for change in population levels, Park et al (2021) suggested that dry periods correspond to lower population levels during the early to late Holocene and that human societies were vulnerable to climate changes. Despite this climatic influence on human activity, it seems difficult to separate the human role (e.g., through deforestation) as a trigger of flooding from natural climate changes in detail due to lack of case studies showing human activity and resultant flooding events during the early to late Holocene.…”

Mid-to-late Holocene climate variability in coastal East Asia and its impact on ancient Korean societies

“…Nevertheless, the exact cause of the culture's rapid decline remains unknown. Recent paleoclimate data from the Korean Peninsula suggest that the cause was climate deterioration around 2800 and 2300 years ago, likely related to changes in WTP SSTs 2,21,54 .…”