Variability of East Asian winter monsoon during Middle–Late Holocene: A study based on a crater lake on Jeju Island, South Korea

Understanding the natural variability of the East Asian monsoon (EAM) system, mainly consisting of summer and winter monsoons, is essential to predict future climate changes that will influence agricultural and industrial activities in the highly populated region. To date, the variability of the East Asian winter monsoon (EAWM) and its controlling factors is still unclear in downwind areas that experience the Siberian High, mostly due to the lack of a high-resolution winter monsoon index. Based on the correlation between diatom variations in a volcanic cone of Jeju Island, South Korea, with past regional climate changes (e.g., temperature, dust, and sea ice) and solar activity, in this study, we evaluated the changes in the climate from the sum of acidophilous species (SAS), known to be mainly controlled by the pH of the prevalent water pool, and inferred that the SAS increased during the cold and dry periods (e.g., Little Ice Age and Dark Age Cold Period). Furthermore, millennial-timescale fluctuation in the detrended SAS during the past 8000 years, with peaks at ~500, 1500, 3000, 5600, 6600, and 7600 cal yr B·P., corresponded to the ice-rafted events reported from studies conducted on subpolar ocean sediments and solar activity. In this study, we suggest that, historically, high-latitude climate change driven by solar activity has controlled the EAWM; additionally, we support the application of the SAS in Jeju Island as a high-resolution EAWM index.