Middle Holocene environmental change in central Korea and its linkage to summer and winter monsoon changes

Abstract

To trace the surficial responses of lowlands to past climate change, we investigated δ13C in total organic carbon (TOC), C/N ratios, magnetic susceptibility (MS), and silicon (Si) intensity (directly proportional to concentration) in wetland sediments collected from the Gimpo area of central Korea, covering 6600–4600 cal yr BP. Two organic layers with high TOC%, negatively depleted δ13CTOC values (− 27 to − 29‰), low MS values, and low Si intensities were found at 6200–5900 and 5200–4800 cal yr BP, respectively. These middle Holocene wet periods corresponded to relatively intensified summer monsoon and solar activity periods. The intervening dry period (5900–5200 cal yr BP) with high MS, high Si, and low TOC% corresponded to an intensified dust-activity interval and stronger winter monsoon. This multi-centennial climatic fluctuation of wet periods (6200–5900 cal yr BP and 5200–4800 cal yr BP) and an intervening dry period (5900–5200 cal yr BP) in central Korea was more synchronous with climate change in the arid inner part of China than with that in South China, suggesting possible strong high-latitude-driven climatic influences (e.g., North Atlantic cooling events) during the middle Holocene.

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

“…7A, B). Similar hydroclimatic changes have been reported based on grain size and geochemical index values from the Gimpo wetland, central Korea (Lim et al, 2015). As shown in Figure 7C, marked increases in total organic carbon levels (%) occurred at 5000 and 6000 cal yr BP, in accordance with depleted δ 13 C values (Fig.…”

“…( B ) Zr/Ti ratios measured via the XRF core scanner from core DSR09 (this study); solid-line superimposed on the Zr/Ti ratios represents the 99-point running average. ( C, D ) Total organic carbon (%) and δ 13 C TOC changes from Gimpo wetland, central Korea (Lim et al, 2015). ( E ) Sea surface temperature (SST) changes in the western Pacific Ocean during the Holocene (Stott et al, 2004).…”

Holocene changes in flooding frequency in South Korea and their linkage to centennial-to-millennial-scale El Niño–Southern Oscillation activity

“…Furthermore, the two wet periods (5800–6400 cal yr BP and 4600–5300 cal yr BP) showing reduced C 4 plants in this study were likely synchronous with those in central Korea. As shown in Figure 9F, the δ 13 C TOC values recovered from the Gimpo wetland sediments clearly revealed two wet periods (Lim et al, 2015). Based on these comparisons (Lim et al, 2014, 2015), the observed long-term increasing trend and significant variability in the time series of the δ 13 C TOC values in this study may be used as a proxy for past climate change, though we cannot completely exclude sedimentological impacts.…”

“…(E) The δ 13 C TOC change in an exposed section on Geoje Island, on the southern coast of Korea (Lim et al, 2014). (F and G) The δ 13 C TOC change and total organic carbon (TOC; %) from Gimpo wetland, central Korea (Lim et al, 2015). (H) Asian summer monsoon index from the oxygen isotope data of stalagmites in Dongge Cave, South China (Dykoski et al, 2005).…”