Holocene Precipitation Change Recorded in Stalagmite Carbon Isotopes and Mg/Ca Ratios in the Pacific Coastal Area of Central Japan

Stalagmite is an excellent archive for reconstructing climate conditions in temperate-tropical areas. Our previous study reconstructed Holocene temperature changes at high resolution from a well-dated stalagmite (KA01) in the Kiriana Cave in Mie Prefecture, Japan, but could not extract information related to precipitation change. Here, the δ¹³C and Mg/Ca ratio of KA01 were used to discuss the precipitation variability. These proxies reflect prior calcite precipitation (PCP; calcite precipitation before the water reaches a stalagmite), which can be used to evaluate the precipitation. The δ¹³C-based PCP with higher time resolution indicates a humid interval of 9.8–7.2 ka and dry intervals of 12.3–13.3 and 4.0–2.0 ka. These humid and dry intervals broadly correspond to the warm and cold intervals, respectively, which were identified in our previous study. This correspondence may have resulted from the oceanographic change in the northwest Pacific, which is dominant moisture and heat sources for the study area. The humid-warm conditions during 9.8–7.2 ka were unstable, with short-term dry and cold periods. The dry and cold period around 8 ka may correspond to the global “8.2 ka event”. The cold-dry period of 4.0–2.0 ka corresponds to the late Jomon period when the population in the Japanese Islands declined. The cold-dry climate is suggested as one of the possible causes for the population decline, and may have spread across a wide area of the Japanese islands. Due to global warming, the future climate along the Pacific coastline is expected to resemble the conditions of the warmest interval in the early-middle Holocene. Considering the high precipitation during this interval, future warming will be accompanied by an increase in precipitation. (273 letters).