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Paleoclimate reconstruction using pollen records from the past 300,000 years in the Tono area, Gifu Prefecture, Central Japan.Dec. 15, 2006The Japan Atomic Energy Agency (JAEA) has, in collaboration with Tohoku Gakuin University (research group of Professor Toyohiko Miyagi), reconstructed the paleoclimate during the past 300,000 years in the Tono area, Gifu Prefecture, Central Japan. JAEA has conducted research to develop methods for precise reconstruction of paleoclimate in an inland area of Japan, as a part of the research for geological disposal of high-level radioactive waste (HLW). As a case study, the pollen species and their compositional ratios in the stratigraphic records in the sediments of the Okute Basin (Mizunami City, Gifu Prefecture) were investigated. The pollen preserved in the sediments of the Okute Basin provide an almost continuous record for the past 300,000 years, because the basin is located near the summit of a hilly area and has not been subjected to erosion by large rivers. Based on the pollen records, paleoclimate of the Tono area has been reconstructed as follows: 300,000 years ago the Tono area had a warm climate, with Beech (Fagus) and Alder (Alnus) forests dominant at that time. Subsequently, rapid cooling occurred and mean annual temperature decreased 5 degrees Celsius. Afterwards, repetitive warm and cool periods occurred every few tens of thousands of years. Tsuga (Tsuga), Firs (Abies), Spruce (Picea) and Pine (Pinus) forests were dominant in the cold period, and a boreal landscape prevailed in the Tono area. Reconstructed paleotemperature during the past 300,000 years in the Okute Basin is consistent with global temperature changes reconstructed from analysis of deep-sea sediments. Consequently, climate change in the Tono area (Central Japan) is consistent with and therefore linked to global temperature changes. Although paleoclimate changes that occurred during the last several tens of thousands of years were reconstructed in many inland areas in Japan, long-term (>300,000 years), continuous reconstructions have had limited success. This research will have a marked impact on paleoclimatology studies and understanding. |
