JpGU-AGU Joint Meeting 2017

Presentation information

[JJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS23] [JJ] Paleoclimatology and paleoceanography

Mon. May 22, 2017 1:45 PM - 3:15 PM IC (International Conference Hall 2F)

convener:Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Ikuko Kitaba(Research Centre for Palaleoclimatology, Ritsumeikan University), Masaki Sano(Research Institute for Humanity and Nature), Chairperson:Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University)

2:15 PM - 2:30 PM

[MIS23-09] High-resolution reconstruction of climates under the three great famines in the Edo period based on intra-ring oxygen isotope ratio of tree rings and historical daily weather record

★Invited papers

*Kenjiro Sho1, Yuta Kojin2, Ikumi Hamada1, Kaoru Kamatani3, Masaki Sano3, Akane Tsushima3, Takeshi Nakatsuka3 (1.Nagoya Institute of Technology, 2.Taisei Corporation, 3.Research Institute for Humanity and Nature)

Keywords:Tree-ring cellulose, Stable oxygen isotope ratio, Intra-ring fluctuation, Relative humidity, The three great famines in the Edo period, Historical daily weather record

Stable oxygen isotope ratio (δ18O) of tree-ring cellulose is known to reflect well relative humidity at the time of ring formation. In this study we attempt high-resolution reconstruction of climates under the three great famines (Kyoho, Tenmei, Tempo) in the Edo period (1603-1867) by analyzing intra-ring data of oxygen isotope ratio of tree-rings. Tree-ring samples used in this study were taken from two hinoki (Chamaecyparis obtusa) trees growing at the Mt.Tanakami site, Shiga Prefecture, central Japan. We extracted cellulose from the wood samples by the “cross-section” method and divided into 12 (or 2, 6, 24, depending on the ring width) segments for each ring using a scalpel. Isotopic measurement was carried out using a continuous flow system with a pyrolysis-type elemental analyzer and an isotope ratio mass spectrometer (TCEA-Delta V Advantage). By comparing measured intra-ring data of cellulose δ18O and observational data of relative humidity at the adjacent meteorological station for the mid- to late 20th century, intra-ring δ18O was found to reflect variation of humidity at sub-seasonal (monthly or finer) temporal resolution in the growth season of the tree (May-Jul. or May-Sep. for our samples). According to this result, we reconstructed variations of humidity for the pre- to early Baiu rainy season (May-Jun.) and the mid- to late Baiu season (Jun.-Jul) usingδ18O chronologies of early part and middle or late part of each ring (Figure). For the pre- to early Baiu season, highly variable δ18O was found in the Kyoho period (1716-1736), implying periodical occurrence of dry early summer caused by delayed onset of the Baiu season. We can also recognize significant decrease in δ18O (increase in humidity) in the Tempo period (1831-1845), probably due to abnormally early onset of the Baiu season. Contrarily, variability of δ18O is relatively small for the mid- to late Baiu season.