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[MIS16-P04] Climate characteristics of Amami , Kagoshima , Japan over the past 200 years inferred from tree-ring cellulose oxygen isotope ratio data
Keywords:Tree-ring cellulose, Oxygen isotope ratio, Relative humidity, Amami Oshima Island, Ryukyu pines
It has become clear that the oxygen isotope ratios contained in tree-ring cellulose reflect oxygen isotope ratios in precipitation and relative humidity , regardless of physiological factors of the tree. It is a useful tool to reconstruct past climate. In this study, we investigate climate characteristics over the past 200 years in Amami Oshima Island(28°22’N 129°29’E), southwestern Japan, by measuring the oxygen isotope ratio contained in tree-ring cellulose.
We collected disk samples from three Ryukyu pine (pinus luchuensis) trees (namely, “Sennen”, ”Santera”, “Untera”). The disk samples were cut into transverse thin plates with a thickness of 2 mm using a diamond wheel saw to extract cellulose. The prepared cellulose specimen was divided into 12 segments for each ring along the growth direction using a binocular stereomicroscope and an ophthalmic knife. We used an online system of a pyrolysis elemental analyzer and an isotope ratio mass spectrometer (TCEA-Delta V Advantage) installed at the Graduate School of Environmental Studies, Nagoya University for isotope measurement. The measured period is Santera pine: 1799 to 1847,1951 to 1967, Sennen pine: 1951 to 1967,1914,1915,1923 to 1927, 1986 to 1994 and Untera pine: 1830 to 1975,1948 to 1952, 1971 to 1990, 2002 to 2013.
To determine the seasonal growth pattern of the three sample trees, we analyzed correlation between intra-ring δ18O variation and 10-day rative humidity data at Naze Meteorological Station (28°22’N 129°29’E) using 37 rings within 1961-2012. As a result, it was estimated that the first segment, corresponding to the earliest stage of tree-ring formation, is formed from early March to mid-April, and the 12th segment, corresponding to the end of tree-ring formation, is formed from late November to late December.
Old document "Oshima Daikanki" (document of prefectural office at Amami Oshima Island) states that there was a long rain from late February to April in 1833, and our oxygen isotope ratio data indicate anomalous wet condition (lowδ18) for the first and second segments of the 1833 ring. Similar resalt was found for the 1804 and 1819 rings, implying about 15-year periodical occurrence of long rain in spring.
We collected disk samples from three Ryukyu pine (pinus luchuensis) trees (namely, “Sennen”, ”Santera”, “Untera”). The disk samples were cut into transverse thin plates with a thickness of 2 mm using a diamond wheel saw to extract cellulose. The prepared cellulose specimen was divided into 12 segments for each ring along the growth direction using a binocular stereomicroscope and an ophthalmic knife. We used an online system of a pyrolysis elemental analyzer and an isotope ratio mass spectrometer (TCEA-Delta V Advantage) installed at the Graduate School of Environmental Studies, Nagoya University for isotope measurement. The measured period is Santera pine: 1799 to 1847,1951 to 1967, Sennen pine: 1951 to 1967,1914,1915,1923 to 1927, 1986 to 1994 and Untera pine: 1830 to 1975,1948 to 1952, 1971 to 1990, 2002 to 2013.
To determine the seasonal growth pattern of the three sample trees, we analyzed correlation between intra-ring δ18O variation and 10-day rative humidity data at Naze Meteorological Station (28°22’N 129°29’E) using 37 rings within 1961-2012. As a result, it was estimated that the first segment, corresponding to the earliest stage of tree-ring formation, is formed from early March to mid-April, and the 12th segment, corresponding to the end of tree-ring formation, is formed from late November to late December.
Old document "Oshima Daikanki" (document of prefectural office at Amami Oshima Island) states that there was a long rain from late February to April in 1833, and our oxygen isotope ratio data indicate anomalous wet condition (lowδ18) for the first and second segments of the 1833 ring. Similar resalt was found for the 1804 and 1819 rings, implying about 15-year periodical occurrence of long rain in spring.