Updated on 2021/11/05

写真a

 
SANO Masaki
 
Organization
Graduate School of Environmental Studies Department of Earth and Environmental Sciences Global Environmental Variation Designated associate professor
Title
Designated associate professor

Degree 1

  1. 博士(農学) ( 2007.2   愛媛大学 ) 

Research Areas 2

  1. Environmental Science/Agriculture Science / Environmental dynamic analysis

  2. Humanities & Social Sciences / Historical studies in general  / 文化財科学

Research History 9

  1. Nagoya University   Graduate School of Environmental Studies   Designated associate professor

    2021.10

  2. Waseda University   Faculty of Human Sciences

    2018.4 - 2020.12

  3. Waseda University   Faculty of Human Sciences   Assistant Professor

    2017.4 - 2018.3

  4. Research Institute for Humanity and Nature

    2014.4 - 2017.3

  5. Research Institute for Humanity and Nature

    2013.10 - 2014.3

  6. 名古屋大学大学院   環境学研究科   日本学術振興会特別研究員(SPD)

    2011.4 - 2013.9

  7. Nagoya University   Graduate School of Environmental Studies

    2009.11 - 2011.3

  8. Ehime University   The United Graduate School of Agricultural Sciences

    2007.4 - 2007.10

  9. Ehime University

    2004.4 - 2006.3

▼display all

Education 1

  1. Ehime University   The United Graduate School of Agricultural Sciences

    - 2007

Professional Memberships 1

  1. 日本文化財科学会

    2018.2

 

Papers 58

  1. Spatial synchrony in δ<sup>18</sup>O time-series from a tree-ring network are driven by synchronous hydroclimate variability in the transitional zone of the Asian summer monsoon

    Fan H., Gou X., Nakatsuka T., Li Z., Su J., Sano M., Liu W., Fang K.

    Agricultural and Forest Meteorology   Vol. 311   2021.12

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    Language:Japanese   Publisher:Agricultural and Forest Meteorology  

    Owing to the increased need to assess global forest behavior under changing climatic conditions within a long-term context, spatial coherence in tree-ring records is of widespread interest. Spatial networks of tree growth have been widely discussed from regional to global scales, but few studies have reported stable oxygen isotopes in networks of tree rings (δ18Otree), thus impeding a comprehensive hydroclimatic interpretation of δ18Otree records over large spatial scales, i.e., isoscapes. In this study, a network of four annually resolved δ18Otree chronologies (1805–2016) was developed for Southwest China, the transitional zone of the Asian summer monsoon, to test spatial coherence in δ18Otree variations and to explore the climatic factors driving synchrony at different spatial scales. The quantitative analyses show that the four chronologies exhibit consistent annual variations, with the first principal component (PC1) accounting for 70% of the total variance, which uniformly respond to local relative humidity (RH) and precipitation δ18O during the monsoon season. This confirms the spatial coherence in δ18Otree records. Furthermore, significant inter-site correlations of local RH and precipitation δ18O are also detected, revealing that it is the regionally homogeneous year-to-year variations in the hydroclimate that should be responsible for spatial coherence. For a larger spatial perspective, spatial correlation analyses reveal that the most prominent correlations between δ18Otree and hydroclimate fields occur in the Indochina Peninsula, in which δ18Otree changes are synchronized with those in Southwest China and the synchrony temporally varies with the Indian summer monsoon (ISM) intensity, indicating that coherent δ18Otree variations are linked to ISM-related moisture transport. In addition, δ18Otree records have shown strong in-phase relationships with the natural variabilities of the ISM and El Niño-Southern Oscillation (ENSO) across interannual and interdecadal timescales over the last 150 years, suggesting that spatial coherence in δ18Otree records can be utilized to reflect the long-term history of large-scale atmospheric circulation.

    DOI: 10.1016/j.agrformet.2021.108687

    Scopus

  2. Tree-ring oxygen isotope across monsoon Asia: Common signal and local influence

    Xu Chenxi, Zhao Qingyu, An Wenling, Wang Simon, Tan Ning, Sano Masaki, Nakatsuka Takeshi, Borhara Krishna, Guo Zhengtang

    QUATERNARY SCIENCE REVIEWS   Vol. 269   2021.10

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    Language:Japanese   Publisher:Quaternary Science Reviews  

    Tree-ring cellulose oxygen isotope (δ18O) in monsoon Asia (MA) is affected collectively by local hydroclimate and remote oceanic-atmospheric variations. Variations of tree-ring δ18O have been widely used for quantitative reconstructions of monsoon-season precipitation, relative humidity and drought severity. However, local hydroclimate and remote large-scale circulation's influences on tree-ring δ18O has not been fully resolved. Here, we collected 24 tree-ring δ18O chronologies covering the period of 1884–1999 across a wide range of MA and investigated the common signals of these chronologies using principal component analysis. The first principal component (PC1) of the 24 tree-ring δ18O chronologies explained 25.2% of the total variances and showed significant positive correlations with the observed Asian summer monsoon oxygen isotope index (r = 0.69) during the period of 1978–1999, suggesting that a common signal of precipitation δ18O does exist in MA and that it is highly correlated with El Niño–Southern Oscillation (ENSO) (r = 0.72) and the South Asian summer monsoon precipitation (r = −0.66). South Asian summer monsoon precipitation and ENSO are the main factors controlling this common signal of tree-ring δ18O across MA. PC1 of tree-ring δ18O chronologies in MA also depicted a negative (positive) correlation with the Atlantic Multidecadal Oscillation (Pacific Decadal Oscillation), indicating the large-scale circulation influences. After removing the large-scale circulation influences on tree-ring δ18O chronologies, however, the residual tree-ring δ18O chronologies exhibit negative correlations with the regional hydroclimate, highlighting the role local hydroclimate on the individual tree-ring δ18O variations.

    DOI: 10.1016/j.quascirev.2021.107156

    Web of Science

    Scopus

  3. Onset and maturation of Asian summer monsoon precipitation reconstructed from intra-annual tree-ring oxygen isotopes from the southeastern Tibetan Plateau Reviewed

    Xu, C, Zhu, H, Wang, S.Y.S, Shi, F, An, W, Li, Z, Sano, M, Nakatsuka, T, Guo, Z

    Quaternary Research   Vol. 103   page: 139 - 147   2021.9

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  4. Ice core drilling on a high-elevation accumulation zone of Trambau Glacier in the Nepal Himalaya

    Tsushima A., Miyahara M., Yamasaki T., Esashi N., Sato Y., Kayastha R.B., Sherpa A.J.B.L., Sano M., Fujita K.

    Annals of Glaciology     page: 1 - 7   2021

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    Language:Japanese   Publisher:Annals of Glaciology  

    We drilled an 81.2-m-long ice core in the accumulation area (5860 m a.s.l.) of Trambau Glacier in the Rolwaling region during October-November 2019. The drilling operation was conducted with a lightweight electro-mechanical drill system after two reconnaissance fieldworks in 2017 and 2018, during which two shallow firn cores were drilled with a hand auger. The drill system and ice core samples were transported by helicopters at a high elevation of 6000 m a.s.l. A further challenging issue was the ice core transportation between Nepal and Japan, as no regular commercial flight was available for the frozen samples. The addition of dry ice imported from India immediately prior to leaving Nepal allowed the ice core samples to be successfully transported to a cold room in Japan, and remain in a frozen state. Stratigraphic observations during the drilling operation suggest the drill site has been affected by melting and refreezing.

    DOI: 10.1017/aog.2021.15

    Scopus

  5. A 2600-year summer climate reconstruction in central Japan by integrating tree-ring stable oxygen and hydrogen in isotopes

    Nakatsuka Takeshi, Sano Masaki, Li Zhen, Xu Chenxi, Tsushima Akane, Shigeoka Yuki, Sho Kenjiro, Ohnishi Keiko, Sakamoto Minoru, Ozaki Hiromasa, Higami Noboru, Nakao Nanae, Yokoyama Misao, Mitsutani Takumi

    CLIMATE OF THE PAST   Vol. 16 ( 6 ) page: 2153 - 2172   2020.11

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    Language:Japanese   Publisher:Climate of the Past  

    Oxygen isotope ratios (δ18O) of tree-ring cellulose are a novel proxy for summer hydroclimate in monsoonal Asia. In central Japan, we collected 67 conifer wood samples, mainly Chamaecyparis obtusa, with ages encompassing the past 2600 years. The samples were taken from living trees, archeological wood, architectural wood, and buried logs. We analyzed stable isotope ratios of oxygen (δ18O) and hydrogen (d2H) in tree-ring cellulose in these samples (more than 15 000 rings in total) without using a pooling method and constructed a statistically reliable treering cellulose δ18O time series for the past 2500 years. However, there were distinct age trends and level offsets in the δ18O record, and cellulose δ18O values showed a gradual decrease as an individual tree matures. This suggested it is difficult to establish a cellulose δ18O chronology for lowfrequency signals by simple averaging of all the δ18O time series data. In addition, there were opposite age trends in the cellulose δ2H, and δ2H gradually increased with tree age. There were clear positive correlations in the short-periodicity variations between δ18O and δ2H, probably indicating a common climate signal. A comparison of the δ18O and δ2H time series in individual trees with tree-ring width suggested that the opposite age trends of δ18O and δ2H are caused by temporal changes in the degree of post-photosynthetic isotope exchange with xylem water (physiological effect), accompanied by changes in stem growth rate that are influenced by human activity in the forests of central Japan. Based on the assumptions that cellulose δ18O and δ2H vary positively and negatively with constant proportional coefficients due to climatological and physiological effects, respectively, we solved simultaneous equations for the climatological and physiological components of variations in tree-ring cellulose δ18O and δ2H in order to remove the age trend. This enabled us to evaluate the climatic record from cellulose δ18O vari ations. The extracted climatological component in the cellulose δ18O for the past 2600 years in central Japan was well correlated with numerous instrumental, historical, and paleoclimatological records of past summer climate at various spatial and temporal scales. This indicates that integration of tree-ring cellulose δ18O and δ2H data is a promising method to reconstruct past summer climate variations on annual to millennial timescales, irrespective of the growth environment. However, analytical and statistical methods need to be improved for further development of this climate proxy.

    DOI: 10.5194/cp-16-2153-2020

    Web of Science

    Scopus

  6. Unstable relationship between tree-ring δ18O in the transitional zone of the Asian summer monsoon and the Indian summer monsoon Reviewed

    Fan, H, Gou, X, Su, J, Liu, W, Gao, L, Nakatsuka, T, Li, Z, Sano, M, Lin, W

    Journal of Hydrology   Vol. 590   page: 125522   2020.11

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  7. A 338-year tree-ring oxygen isotope record from Thai teak captures the variations in the Asian summer monsoon system Reviewed

    Pumijumnong, N, Bräuning, A, Sano, M, Nakatsuka, T, Muangsong, C, Buajan, S

    Scientific Reports   Vol. 10 ( 1 ) page: 8966   2020.6

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  8. Climate variability over the past 100 years in Myanmar derived from tree-ring stable oxygen isotope variations in Teak Reviewed

    Pumijumnong, N, Muangsong, C, Buajan, S, Sano, M, Nakatsuka, T

    Theoretical and Applied Climatology   Vol. 139 ( 3-4 ) page: 1401 - 1414   2020.2

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  9. Summer monsoon variability in the Himalaya over recent centuries Invited Reviewed

    Sano, M, Xu, C, Dimri, A.P, Ramesh, R

    In: A.P. Dimri, B. Bookhagen, M. Stoffel and T. Yasunari (Eds.), Himalayan weather and climate and their impact on the environment. Springer International Publishing, Cham     page: 261 - 280   2020

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  10. 酸素同位体比年輪年代法による高屋敷館遺跡東壕橋脚の年代検証

    箱﨑真隆, 木村淳一, 木村勝彦, 佐野雅規, 對馬あかね, 李貞, 中塚武

    青森市埋蔵文化財調査報告書   ( 124 ) page: 77 - 80   2019.3

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    Language:Japanese   Publishing type:Research paper (bulletin of university, research institution)  

  11. Increased drought events in southwest China revealed by tree ring oxygen isotopes and potential role of Indian Ocean Dipole Reviewed

    Xu, C, An, Wenlin, Wang, S.Y.S, Yi, L, Ge, J, Nakatsuka, T, Sano, M, Guo, Z

    Science of The Total Environment   Vol. 661   page: 645 - 653   2019

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    Language:English  

    DOI: 10.1016/j.scitotenv.2019.01.186

    PubMed

  12. 年輪を用いた南アルプスにおける1774年以降の夏期気温の復元 Reviewed

    安江恒, 久保典子, 赤尾実紀子, 佐野雅規, 中塚武

    地学雑誌   Vol. 128   page: 49 - 59   2019

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  13. Specific response of earlywood and latewood δ18O from the east and west of Mt. Qomolangma to the Indian summer monsoon Reviewed

    An, W, Xu, C, Liu, X, Tan, N, Sano, M, Li, M, Shao, X, Nakatsuka, T, Guo, Z

    Science of The Total Environment   Vol. 689   page: 99 - 108   2019

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    Language:English  

    DOI: 10.1016/j.scitotenv.2019.06.268

    PubMed

  14. Oxygen isotope ratios of subalpine conifers in Jirisan National Park, Korea and their dendroclimatic potential Reviewed

    Seo, J.-W, Sano, M, Jeong, H.-M, Lee, K.-H, Park, H.-C, Nakatsuka, T, Shin, C.-S

    Dendrochronologia   Vol. 57   page: 125626   2019

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  15. Increased variability of Thailand's Chao Phraya River peak season flow and its association with ENSO variability: Evidence from tree ring δ18O Reviewed

    Xu, C, Buckley, B.M, Promchote, P, Wang, S.-Y.S, Pumijumnong, N, An, W, Sano, M, Nakatsuka, T, Guo, Z

    Geophysical Research Letters   Vol. 46   page: 4863 - 4872   2019

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  16. Cellulose oxygen isotopic composition of teak (Tectona grandis) collected from Java Island: a tool for dendrochronological and dendroclimatological analysis Reviewed

    Hisamochi, R, Watanabe, Y, Sano, M, Nakatsuka, T, Kurita, N, Matsuo-Ueda, M, Yamamoto, H, Tazuru, S, Sugiyama, J, Subiyanto, B, Marsoem, S.N, Tsuda, T, Tagami, T

    Dendrochronologia   Vol. 52   page: 80 - 86   2018.12

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  17. Decreasing Indian summer monsoon on the northern Indian sub-continent during the last 180 years: Evidence from five tree-ring cellulose oxygen isotope chronologies Reviewed

    Chenxi Xu, Masaki Sano, Ashok Priyadarshan DImri, Rengaswamy Ramesh, Takeshi Nakatsuka, Feng Shi, Zhengtang Guo

    Climate of the Past   Vol. 14 ( 5 ) page: 653 - 664   2018.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Copernicus GmbH  

    We have constructed a regional tree-ring cellulose oxygen isotope (δ18O) record for the northern Indian sub-continent based on two new records from northern India and central Nepal and three published records from northwestern India, western Nepal and Bhutan. The record spans the common interval from 1743 to 2008 CE. Correlation analysis reveals that the record is significantly and negatively correlated with the three regional climatic indices: all India rainfall (AIR
    r = -0.5, p &lt
    0.001, n = 138), Indian monsoon index (IMI
    r = -0.45, p &lt
    0.001, n = 51) and the intensity of monsoonal circulation (r = -0.42, p &lt
    0.001, n = 51). The close relationship between tree-ring cellulose δ18O and the Indian summer monsoon (ISM) can be explained by oxygen isotope fractionation mechanisms. Our results indicate that the regional tree-ring cellulose δ18O record is suitable for reconstructing high-resolution changes in the ISM. The record exhibits significant interannual and long-term variations. Interannual changes are closely related to the El Niño-Southern Oscillation (ENSO), which indicates that the ISM was affected by ENSO in the past. However, the ISM-ENSO relationship was not consistent over time, and it may be partly modulated by Indian Ocean sea surface temperature (SST). Long-term changes in the regional tree-ring δ18O record indicate a possible trend of weakened ISM intensity since 1820. Decreasing ISM activity is also observed in various high-resolution ISM records from southwest China and Southeast Asia, and may be the result of reduced land-ocean thermal contrasts since 1820 CE.

    DOI: 10.5194/cp-14-653-2018

    Scopus

  18. Early summer precipitation in the lower Yangtze River basin for AD 1845–2011 based on tree-ring cellulose oxygen isotopes Reviewed

    Chenxi Xu, Jiangfeng Shi, Yesi Zhao, Takeshi Nakatsuka, Masaki Sano, Shiyuan Shi, Zhengtang Guo

    Climate Dynamics   Vol. xx ( xx ) page: 1 - 12   2018.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Verlag  

    Precipitation from June to August is generally used to reflect the East Asian summer monsoon (EASM) variability. However, the principal modes of the EASM rainfall are different between May–June (MJ) and July–August due to the seasonal march of East Asian subtropical front. Therefore, it is necessary to study them separately. In this study, we reconstruct a 167-year MJ precipitation time series using tree-ring cellulose δ18O that explains 46.9% of the variance in the lower Yangtze River basin, Southeast China, that extends the meteorological data back more than 100 years and makes the precipitation study at decadal scales possible. The decades with 5 or more anomalously dry or wet years are the 1880s, 1890s, and 1910s, and the 1980s and 2000s have only one anomalous year per decade. MJ precipitation shows a significantly negative relationship with absolute Niño 3.4 sea surface temperature, especially during the developing phases of El Niño-Southern Oscillation, indicating that there is less rainfall during El Niño events. However, the relationship is not uniform throughout the period. Further analyses show that it is stronger when the Pacific Decadal Oscillation is in its positive phases.

    DOI: 10.1007/s00382-018-4212-5

    Scopus

  19. Age determination on a catastrophic rock avalanche using tree-ring oxygen isotope ratios - the scar of a historical gigantic earthquake in the Southern Alps, central Japan Reviewed

    Ryuji Yamada, Yoshihiko Kariya, Takashi Kimura, Masaki Sano, Zhen Li, Takeshi Nakatsuka

    Quaternary Geochronology   Vol. 44   page: 47 - 54   2018.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier B.V.  

    Dendrochronological analysis using the oxygen isotope composition (18O/16O) of cellulose was performed to reveal the age of an ancient rock avalanche that scattered huge granitic rock clasts on the bank of the Dondokosawa River in the east of Mount Hououzan, the Akaishi Range, central Japan. The samples for dating were disc-cut wood logs or increment cores of Japanese cypress (Chamaecyparis obtusa (Sieb. &amp
    Zucc.) Endl.) and Hemlock tree (Tsuga sp.) buried in lacustrine sediments. Cellulose was extracted directly from tree-ring cross-sectional thin wood plates. Cellulose rings of each disc were sampled and their oxygen isotope ratios were measured with a pyrolysis-type elemental analyser and an isotope ratio mass spectrometer. We compared the inter-annual variations in oxygen isotope ratios of cellulose for samples with those of a 470-year-long tree-ring δ18O chronology (AD450–919) independently constructed from Japanese cypress. The estimated death year of the barkless Japanese cypress is around AD885, and that of the barked hemlock tree is AD888. If the rock avalanche was induced by strong ground motion from a large earthquake, these ages are relevant to a large historical earthquake that occurred in this area. The candidates are the AD 887 Goki-Shichido Earthquake (Ninna Earthquake), which was one of the gigantic ocean-trench earthquakes documented along the Suruga and Nankai Troughs off central Japan, and another large intraplate earthquake remotely triggered by this ocean-trench earthquake.

    DOI: 10.1016/j.quageo.2017.12.004

    Scopus

  20. 三内丸山遺跡出土木材の酸素同位体分析と年代研究

    小林謙一, 木村勝彦, 箱﨑真隆, 佐野雅規, 中塚武

    特別史跡三内丸山遺跡年報21     page: 62 - 80   2018.3

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    Language:Japanese   Publishing type:Research paper (bulletin of university, research institution)  

  21. 年輪酸素同位体比分析による多賀城の柵木の年代決定

    斎藤颯人, 木村勝彦, 箱﨑真隆, 佐野雅規, 對馬あかね, 李貞, 中塚武

    宮城県多賀城跡調査研究所年報2017多賀城跡     page: 42 - 45   2018.3

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    Language:Japanese   Publishing type:Research paper (bulletin of university, research institution)  

  22. A 180-year-long isotopic record of tree-ring cellulose on Okinawa Island, Japan Reviewed

    Uemura, R, Uemura, M, Sano, M, Nakatsuka, T

    Geochemical Journal   Vol. 52   page: e21 - e27   2018

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  23. Evaluation of the effect of the 2011 Tsunami on coastal forests by means of multiple isotopic analyses of tree rings Reviewed

    Lopez, C.M.L, Nakano, S, Ferrio, J.P, Hayashi, M, Nakatsuka, T, Sano, M, Yamanaka T, Nobori Y

    Isotopes in Environmental and Health Studies   Vol. 54 ( 5 ) page: 494 - 507   2018

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    Language:English  

    DOI: 10.1080/10256016.2018.1495203

    PubMed

  24. 気候変動と米収量の比較から探る近世日本の社会 Invited Reviewed

    佐野雅規, 鎌谷かおる, 中塚武

    考古学ジャーナル   Vol. 715   page: 34 - 39   2018

  25. Sample preparation of ring-less tropical trees for δ18O measurement in isotope dendrochronology Reviewed

    Nakai, W, Okada, N, Sano, M, Nakatsuka, T

    Tropics   Vol. 27   page: 49 - 58   2018

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  26. Inter-annual and multi-decadal variability of monsoon season rainfall in central Thailand during the period 1804–1999, as inferred from tree ring oxygen isotopes Reviewed

    Xu, C, Pumijumnong, N, Nakatsuka, T, Sano, M, Guo, Z

    International Journal of Climatology   Vol. xx   page: xx - xx   2018

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  27. Negligible local-factor influences on tree ring cellulose delta O-18 of Qilian juniper in the Animaqing Mountains of the eastern Tibetan Plateau Reviewed

    Chenxi Xu, Xuemei Shao, Wenling An, Takeshi Nakatsuka, Yong Zhang, Masaki Sano, Zhengtang Guo

    TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY   Vol. 69   page: 1391663   2017.11

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:TAYLOR & FRANCIS LTD  

    Tree ring cellulose oxygen isotopes (delta O-18) were measured on 21 trees of Qilian juniper from the Animaqing Mountains, Tibetan Plateau, to investigate intra-and inter-tree variability, potential juvenile and elevation effects and climatic implications. There are no significant differences in mean and standard deviation of tree ring delta O-18 values at different heights in individual trees. Tree ring delta O-18 values from different directions show a high degree of coherence. The mean and standard deviation for vertical and circumferential delta O-18 time series are very similar, and delta O-18 data from different heights and directions are highly correlated (r &gt; 0.88). The delta O-18 values of young trees are lower than those of old trees in the first 10 years of tree growth. Tree ring delta O-18 data from five different altitudes are highly correlated (r &gt; 0.88) and share similar climatic signals. As such, an altitude effect on tree ring delta O-18 is not observed. Our results indicate that samples from one site, regardless of sampling height, direction or altitude, can be used to reconstruct a long-term delta O-18 record. Tree ring delta O-18 data from the Animaqing Mountains show a significant negative correlation (r = -0.67; p &lt; 0.001) with May-July regional precipitation and appear to be a promising proxy for precipitation reconstruction.

    DOI: 10.1080/16000889.2017.1391663

    Web of Science

  28. Moisture source signals preserved in a 242-year tree-ring delta O-18 chronology in the western Himalaya Reviewed

    Masaki Sano, A. P. Dimri, R. Ramesh, Chenxi Xu, Zhen Li, Takeshi Nakatsuka

    GLOBAL AND PLANETARY CHANGE   Vol. 157   page: 73 - 82   2017.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE BV  

    The oxygen isotope ratio (delta O-18) of tree-ring cellulose is known to be a reliable proxy for hydroclimate in monsoon Asia. However, tree-ring delta O-18 data are still spatially and temporally limited, so a denser tree-ring network in Asia is required to better understand the dynamics of the monsoon circulation and its past variability. Here, we present a 242-year delta O-18 chronology calculated from five silver fir trees collected in the western (Indian) Himalaya, a region located on the northwestern periphery of the summer monsoon incursions. Response analyses using regionalized climatic data revealed that tree-ring delta O-18 is controlled by hydroclimatic variables, including precipitation, relative humidity, and the drought index, during the summer monsoon season. In addition, spatial correlation analyses with gridded climatic parameters showed that the strongest correlations of tree-ring delta O-18 are not observed with the climatic parameters at the sampling site, but with those in a region several hundred kilometers to the southwest, indicating that water vapor originating in the Arabian Sea is transported to the study site. Based on these results, we reconstructed the self-calibrating Palmer Drought Severity Index (scPDSI) for the summer monsoon season (June-September) over the past 242 years (1767-2008 CE), using a linear regression model that accounts for 45.0% of the actual scPDSI variance. Our chronology showed significant correlations with other tree-ring delta O-18 data from Nepal and Bhutan, indicating that common signals related to the moisture supply from the Bay of Bengal are also recorded in the present reconstruction. However, the tree-ring record from India often showed weak correlations with that from Bhutan, especially when the summer monsoon was relatively weak. This result, together with the fact that the water vapor at the tree site was also derived from the Arabian Sea, implies that a weaker monsoon circulation enhances the flux of Arabian Sea moisture and reduces the flux of Bay of Bengal moisture to the study region.

    DOI: 10.1016/j.gloplacha.2017.08.009

    Web of Science

  29. Data Descriptor: A global multiproxy database for temperature reconstructions of the Common Era Reviewed

    Julien Emile-Geay, Nicholas P. McKay, Darrell S. Kaufman, Lucien von Gunten, Jianghao Wang, Kevin J. Anchukaitis, Nerilie J. Abram, Jason A. Addison, Mark A. J. Curran, Michael N. Evans, Benjamin J. Henley, Zhixin Hao, Belen Martrat, Helen V. McGregor, Raphael Neukom, Gregory T. Pederson, Barbara Stenni, Kaustubh Thirumalai, Johannes P. Werner, Chenxi Xu, Dmitry V. Divine, Bronwyn C. Dixon, Joelle Gergis, Ignacio A. Mundo, Takeshi Nakatsuka, Steven J. Phipps, Cody C. Routson, Eric J. Steig, Jessica E. Tierney, Jonathan J. Tyler, Kathryn J. Allen, Nancy A. N. Bertler, Jesper Bjorklund, Brian M. Chase, Min-Te Chen, Ed Cook, Rixt de Jong, Kristine L. DeLong, Daniel A. Dixon, Alexey A. Ekaykin, Vasile Ersek, Helena L. Filipsson, Pierre Francus, Mandy B. Freund, Massimo Frezzotti, Narayan P. Gaire, Konrad Gajewski, Quansheng Ge, Hugues Goosse, Anastasia Gornostaeva, Martin Grosjean, Kazuho Horiuchi, Anne Hormes, Katrine Husum, Elisabeth Isaksson, Selvaraj Kandasamy, Kenji Kawamura, K. Halimeda Kilbourne, Nalan Koc, Guillaume Leduc, Hans W. Linderholm, Andrew M. Lorrey, Vladimir Mikhalenko, P. Graham Mortyn, Hideaki Motoyama, Andrew D. Moy, Robert Mulvaney, Philipp M. Munz, David J. Nash, Hans Oerter, Thomas Opel, Anais J. Orsi, Dmitriy V. Ovchinnikov, Trevor J. Porter, Heidi A. Roop, Casey Saenger, Masaki Sano, David Sauchyn, Krystyna M. Saunders, Marit-Solveig Seidenkrantz, Mirko Severi, Xuemei Shao, Marie-Alexandrine Sicre, Michael Sigl, Kate Sinclair, Scott St George, Jeannine-Marie St Jacques, Meloth Thamban, Udya Kuwar Thapa, Elizabeth R. Thomas, Chris Turney, Ryu Uemura, Andre E. Viau, Diana O. Vladimirova, Eugene R. Wahl, James W. C. White, Zicheng Yu, Jens Zinke

    SCIENTIFIC DATA   Vol. 4 ( Article number: 170088 )   2017.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATURE PUBLISHING GROUP  

    Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high-and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python.
    (TABLE)
    Since the pioneering work of D'Arrigo and Jacoby1-3, as well as Mann et al. 4,5, temperature reconstructions of the Common Era have become a key component of climate assessments6-9. Such reconstructions depend strongly on the composition of the underlying network of climate proxies10, and it is therefore critical for the climate community to have access to a community-vetted, quality-controlled database of temperature-sensitive records stored in a self-describing format. The Past Global Changes (PAGES) 2k consortium, a self-organized, international group of experts, recently assembled such a database, and used it to reconstruct surface temperature over continental-scale regions11 (hereafter, ` PAGES2k-2013').
    This data descriptor presents version 2.0.0 of the PAGES2k proxy temperature database (Data Citation 1). It augments the PAGES2k-2013 collection of terrestrial records with marine records assembled by the Ocean2k working group at centennial12 and annual13 time scales. In addition to these previously published data compilations, this version includes substantially more records, extensive new metadata, and validation. Furthermore, the selection criteria for records included in this version are applied more uniformly and transparently across regions, resulting in a more cohesive data product.
    This data descriptor describes the contents of the database, the criteria for inclusion, and quantifies the relation of each record with instrumental temperature. In addition, the paleotemperature time series are summarized as composites to highlight the most salient decadal-to centennial-scale behaviour of the dataset and check mutual consistency between paleoclimate archives. We provide extensive Matlab code to probe the database-processing, filtering and aggregating it in various ways to investigate temperature variability over the Common Era. The unique approach to data stewardship and code-sharing employed here is designed to enable an unprecedented scale of investigation of the temperature history of the Common Era, by the scientific community and citizen-scientists alike.

    DOI: 10.1038/sdata.2017.88

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  30. スギ・ヒバの出土材の年輪を用いた秋田・青森の気候復元の可能性

    窪田優一, 箱﨑真隆, 木村勝彦, 佐野雅規, 中塚武, 木村淳一, 小林謙一, 安江恒

    第19回AMSシンポジウム・2016年度「樹木年輪」研究会共同開催シンポジウム報告集     page: 136 - 138   2017.6

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  31. Sampling strategy and climatic implication of tree-ring cellulose oxygen isotopes of Hippophae tibetana and Abies georgei on the southeastern Tibetan Plateau Reviewed

    Chenxi Xu, Haifeng Zhu, Takeshi Nakatsuka, Masaki Sano, Zhen Li, Feng Shi, Eryuan Liang, Zhengtang Guo

    International Journal of Biometeorology   Vol. XX ( 5 ) page: 1 - 8   2017.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer New York LLC  

    The tree-ring cellulose oxygen isotopes (δ18O) for four trees of Hippophae tibetana and four trees of Abies georgei growing in different locations around the terminal moraine in Xincuo from 1951 to 2010 were measured to explore its potential for reconstructing climatic variations in the southeastern Tibetan Plateau. The mean and standard deviation of tree-ring δ18O at different heights do not have significant differences, and there are no significant differences in the mean and standard deviation of tree-ring δ18O between trees near the brook and trees at the top of moraine, indicating that we can collect samples for tree-ring δ18O analysis regardless of sampling heights and that the micro-environment does not affect tree-ring δ18O significantly. The mean inter-series correlations of cellulose δ18O for A. georgei/H. tibetana are 0.84/0.93, and the correlation between δ18O for A. georgei and H. tibetana is 0.92. The good coherence between inter-tree and inter-species cellulose δ18O demonstrates the possibility of using different species to develop a long chronology. Correlation analysis between tree-ring δ18O and climate parameters revealed that δ18O for A. georgei/H. tibetana had negative correlations (r = −0.62/r = −0.69) with relative humidity in July–August, and spatial correlation revealed that δ18O for A. georgei/H. tibetana reflected the regional Standardized Precipitation Evapotranspiration Index (29°–32° N, 88°–98° E). In addition, tree-ring δ18O in Xincuo has a significant correlation with tree-ring δ18O in Bhutan. The results indicate that cellulose δ18O for A. georgei and H. tibetana in Xincuo is a good proxy for the regional hydroclimate.

    DOI: 10.1007/s00484-017-1365-6

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    PubMed

  32. Establishing tree ring δ18O chronologies for principle tree species (T. Cuspidata, P. Koraiensis, A. Koreana, Q. Mongolica) at subalpine zone in Mt. Jiri national park and their correlations with the corresponding climate Reviewed

    Jeong-Wook Seo, Hyun-Min Jeong, Masaki Sano, En-Bi Choi, Jun-Hui Park, Kwang-Hee Lee, Yo-Jung Kim, Hong-Chul Park

    Journal of the Korean Wood Science and Technology   Vol. 45 ( 5 ) page: 661 - 670   2017

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    50-year tree-ring δ18O chronologies (1966∼2015) for principle conifer tree species (Taxus cuspidata, Pinus koraiensis, Abies koreana) and Quercus mongolica at subalpine zone in Mt. Jiri were established. The establishing of tree-ring δ18O chronologies for each tree species were fulfilled using four trees, which showed the good result in cross-dating. In the comparisons between tree-ring δ18O chronologies within the same tree species all tree species showed reliable results statistically (p &lt
    0.001), and they also showed EPS higher than 0.85. In addition to, the reliable correlations (p &lt
    0.001) were verified between tree-ring δ18O chronologies of four tree species, as well. In the response function analysis in order to investigate the relationships between tree-ring δ18O chronologies and corresponding climatic factors, i.e., monthly precipitation and mean temperature, T. cuspidata showed a negative correlation with May precipitation (p &lt
    0.05) and A. koreana showed a negative correlation with April precipitation (p &lt
    0.05). If long tree-ring δ18O chronologies of T. cuspidata and A. koreana will be established, it will be possible to reconstruct April and May precipitation in the past when we have no the meteorological data.

    DOI: 10.5658/WOOD.2017.45.5.661

    Scopus

  33. 近世後期の琉球における気候変動災害の展開と社会応答 —1780年代の災害と上からの村落立て直し— Reviewed

    山田浩世, 佐野雅規

    首里城研究   Vol. 19   page: 4 - 19   2017

  34. Reconstruction of short and long term variations of summer precipitation in central Japan by integrating of oxygen and hydrogen isotope ratios of tree ring cellulose

    Nakatsuka Takeshi, Sano Masaki, Li Zhen, Tsushima Akane, Shigeoka Yuki

    Abstracts of Annual Meeting of the Geochemical Society of Japan   Vol. 64 ( 0 )   2017

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    <p></p>

    DOI: 10.14862/geochemproc.64.0_15

  35. Inter- and intra-annual tree-ring cellulose oxygen isotope variability in response to precipitation in Southeast China Reviewed

    Chenxi Xu, Huaizhou Zheng, Takeshi Nakatsuka, Masaki Sano, Zhen Li, Junyi Ge

    TREES-STRUCTURE AND FUNCTION   Vol. 30 ( 3 ) page: 785 - 794   2016.6

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    Compared with annual tree-ring cellulose delta (18) O, intra-annual cellulose delta (18) O has potential to reconstruct precipitation with higher resolution and stronger signal intensity.
    Annual tree-ring cellulose oxygen isotope values (delta O-18) of Fokienia hodginsii provide a promising proxy of monsoon-season precipitation in Southeast China. Measuring intra-annual cellulose delta O-18 values may reveal the seasonal variability of precipitation and the associated climate influences. Here, we examine intra-annual variation of cellulose delta O-18 values in Fokienia hodginsii and Cryptomeria fortune from Fujian Province, Southeast China. Both species exhibited considerable intra-annual variations in cellulose delta O-18 (range similar to 6 aEuro degrees) with a consistent pattern of enriched values near the annual ring boundary and depleted values in the central portion of the ring. Seasonal patterns in the tree-ring delta O-18 values generally followed changes in precipitation delta O-18 values. Compared with annual tree-ring cellulose delta O-18, intra-annual cellulose delta O-18 has potential to reconstruct precipitation with higher resolution and stronger signal intensity. July tree-ring cellulose delta O-18 is significantly correlated (r = -0.58, p &lt; 0.05) with July precipitation, and June-August tree-ring cellulose delta O-18 and annual tree-ring cellulose delta O-18, respectively, explain 52 and 41 % of the actual variance of April-August precipitation. In addition, May-October cellulose delta O-18 values during El Nio years are higher than in La Nia years, and April to October rainfall is lower in El Nio years than in La Nia years. Combining the significant correlations between inter-annual cellulose delta O-18 values and sea surface temperatures in the central tropical Pacific, our results support the hypothesis that El Nio-Southern Oscillation affects tree-ring cellulose delta O-18 in Southeast China by modulating seasonal precipitation.

    DOI: 10.1007/s00468-015-1320-2

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  36. Potential utility of tree ring delta O-18 series for reconstructing precipitation records from the lower reaches of the Yangtze River, southeast China Reviewed

    Chenxi Xu, Junyi Ge, Takeshi Nakatsuka, Liang Yi, Huaizhou Zheng, Masaki Sano

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   Vol. 121 ( 8 ) page: 3954 - 3968   2016.4

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    In this study, we investigated the interannual and intraannual variabilities in the oxygen isotope composition (delta O-18) preserved in the tree ring cellulose of Pinus taiwanensis in the lower reaches of the Yangtze River, southeast China, to explore its potential utility for precipitation reconstruction over the period of 1855-2013. Intraannual variations of tree ring cellulose delta O-18 show distinct annual cycles that are characterized by delta O-18 maxima in the early growth near the ring boundary and delta O-18 minima in the middle and late portions of the ring. Seasonal patterns of tree ring delta O-18 were influenced by August-October typhoons. The tree ring cellulose delta O-18 was measured in both young and old trees to test for the juvenile effect. The results revealed no significant differences in the mean values and long-term trends in delta O-18 in the old and young trees. A response analysis indicated that tree ring delta O-18 correlated significantly with precipitation and relative humidity between May and October, and the delta O-18 chronology accounted for 37.4% of the actual variation in the May-October precipitation between 1951 and 2013. The extremely dry and wet years revealed by the tree ring delta O-18-based reconstructed precipitation also corresponded to actual local drought and flood events from the documentary records. Reconstructed precipitation showed significant relationship with central tropical Pacific sea surface temperature, which indicated that El Nino-Southern Oscillation (ENSO) exerted influences on May-October precipitation in the lower reaches of the Yangtze River. In addition, the relationship between ENSO and precipitation weakened between 1920 and 1940, and low variance of ENSO from 1920 to 1940 may result in the damped ENSO's influences on precipitation in southeast China.

    DOI: 10.1002/2015JD023610

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  37. 西暦774-775年の14Cイベントと酸素同位体比年輪年代法に基づく青森市新田(1)遺跡アスナロ材の暦年代の検証

    箱﨑真隆, 中村俊夫, 大山幹成, 木村淳一, 佐野雅規, 中塚武

    名古屋大学加速器質量分析計業績報告書   Vol. XVII   page: 34 - 39   2016.3

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  38. 日本近世における年貢上納と気候変動 —近世史研究における古気候データ活用の可能性をさぐる— Invited Reviewed

    鎌谷かおる, 佐野雅規, 中塚武

    日本史研究   Vol. 646   page: 36 - 56   2016

  39. A tree-ring cellulose delta O-18-based July-October precipitation reconstruction since AD 1828, northwest Thailand Reviewed

    Chenxi Xu, Nathsuda Pumijumnong, Takeshi Nakatsuka, Masaki Sano, Zhen Li

    JOURNAL OF HYDROLOGY   Vol. 529 ( P2 ) page: 433 - 441   2015.10

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    A tree-ring delta O-18 chronology for the period 1828-2000 was developed from four Pinus merkusii trees, to find a reliable proxy for reconstructing precipitation in northwest Thailand. Inter-tree delta O-18 correlations were high during the entire period (r = 0.57-0.79). The tree-ring delta O-18 chronology shows significant negative correlations with regional July-October precipitation during the period 1901-2000 (r = -0.62) and with July-October river flow (r = -0.54), and is in good agreement with a shorter tree-ring delta O-18 chronology from living Pinus kesiya in northwest Thailand. The spatial correlation analysis between tree-ring delta O-18 and regional July-October precipitation also support that the tree-ring delta O-18 of P. merkusii is a promising proxy to reconstruct precipitation in northwest Thailand. The tree-ring delta O-18-based July-October reconstruction, which accounts for 37.6% of the precipitation variance, shows a close relationship with El Nino-Southern Oscillation (ENSO) during the period 1871-2000, with the exception of during the past two decades; the exception may be related to the southeastward shift of the descending limb of Walker circulation and increased frequency of central Pacific ENSO. (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jhydrol.2015.02.037

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  40. A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium Reviewed

    Feng Shi, Quansheng Ge, Bao Yang, Jianping Li, Fengmei Yang, Fredrik Charpentier Ljungqvist, Olga Solomina, Takeshi Nakatsuka, Ninglian Wang, Sen Zhao, Chenxi Xu, Keyan Fang, Masaki Sano, Guoqiang Chu, Zexin Fan, Narayan P. Gaire, Muhammad Usama Zafar

    CLIMATIC CHANGE   Vol. 131 ( 4 ) page: 663 - 676   2015.8

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    To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June-July-August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400.

    DOI: 10.1007/s10584-015-1413-3

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  41. An optimized method for stable isotope analysis of tree rings by extracting cellulose directly from cross-sectional laths Reviewed

    Akira Kagawa, Masaki Sano, Takeshi Nakatsuka, Tsutomu Ikeda, Satoshi Kubo

    CHEMICAL GEOLOGY   Vol. 393-394   page: 16 - 25   2015.1

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    Stable isotopes in tree-ring alpha-cellulose are valued as environmental proxies and their use is steadily increasing; however, preparation of alpha-cellulose is a bottleneck in isotope analysis. Recent methodological breakthrough for extracting tree-ring alpha-cellulose directly from tree-ring cross-sectional laths drastically increased the throughput of tree-ring isotope data. In this paper, we evaluate our recently designed "cross-section" method. This method employs polytetrafluoroethylene (PTFE) cases, enabling direct extraction of alpha-cellulose from 1-mm thick tree-ring laths, in combination with fixation sheets to prevent disintegration of freeze-dried alpha-cellulose laths. Perforated PTFE cases are easily producible at an affordable cost. They are made of commonly available lab consumables in catalogs and do not require specially made PTFE parts. Freeze-dried alpha-cellulose laths preserved distinct anatomical structure, enabling precise separation at the tree-ring boundaries. Once separated froma lath, tree-ring alpha-cellulose can beweighed directly into silver or tin capsules for analysis. We checked chemical purity of alpha-cellulose prepared by the cross-section method from five tree species (larch, pine, spruce, beech, and oak). Residual lignin and hemicellulose contents were quantitatively assessed by Fourier transforminfrared spectrometry and gas chromatography. The average chemical purity of alpha-cellulose laths from the five species was 94.5%, similar to the chemical purity of alpha-cellulose prepared with the standard Jayme-Wise method. Both oxygen and carbon isotope values of alpha-cellulose prepared by the cross-section method also closely matched those prepared by the standard method. We conclude that, by overhauling the method of alpha-cellulose preparation for tree-ring isotope analysis, we increased throughput of tree-ring oxygen and carbon isotope data without sacrificing sample purity. (c) 2014 The Authors. Published by Elsevier B.V.

    DOI: 10.1016/j.chemgeo.2014.11.019

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  42. Tree-ring cellulose delta O-18 variability in pine and oak and its potential to reconstruct precipitation and relative humidity in central Japan Reviewed

    Zhen Li, Takeshi Nakatsuka, Masaki Sano

    GEOCHEMICAL JOURNAL   Vol. 49 ( 2 ) page: 125 - 137   2015

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    Oxygen isotope ratios (delta O-18) of tree-ring cellulose in pine (Pinta densiflora) and oak (Quercus serrate and Quercus variabilis) growing in central Japan from 1970 to 2011 share a common inter-annual variance among different cores in a tree, different trees in a species, and different species in a forest. The high mean correlation between the two radii ((r) over bar = 0.738) of individual trees and the mean standard deviation of two measurements for the same year from the two radii of eight trees ((sigma) over bar = 0.361 parts per thousand) reveals the reliability and representativeness of single cores. The significant correlation (r = 0.667, p &lt; 0.01) between pine and oak cellulose delta O-18 suggests that delta O-18 in tree-ring cellulose is controlled by common external factors, and that it is possible to establish a unique delta O-18 chronology using different tree species. The delta O-18 values of tree-ring cellulose in pine and oak trees are negatively correlated with precipitation from June to August (correlation coefficients are -0.679 for pine and -0.583 for oak), which is attributable to the precipitation amount effect, mainly caused by the stagnant rain front (Baiu) in early summer and typhoons in late summer in this region. The delta O-18 values are negatively correlated with relative humidity from April to September for pine (r = -0.632, p &lt; 0.01), and in June and July for oak (r = -0.437, p &lt; 0.01); these correlations probably reflect different lengths of the growing season. Multiple regression analysis reveals that tree-ring delta O-18 values of pine and oak in this region are largely governed by summer precipitation. Relative humidity does not appear to greatly affect tree-ring delta O-18 of oak, in contrast to pine, which may be interpreted in terms of differences in leaf morphology and/or cellulose synthesis processes. Our results indicate that delta O-18 values of tree-ring cellulose can provide a potential crossdating tool, irrespective of the physiological differences between gymnosperms and angiosperms. In central Japan, tree-ring delta O-18 values of both pine and oak can act as reliable proxies of June August precipitation, while pine trees tend to exhibit more potential for reconstruction of relative humidity.

    DOI: 10.2343/geochemj.2.0336

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    Scopus

  43. Hydroclimate variability over last two and a half centuries inferred from oxygen isotope records of Abies homolepis tree-ring in Shikoku, southwestern Japan

    LI Zhen, Nakatsuka Takeshi, Sano Masaki

    Abstracts of Annual Meeting of the Geochemical Society of Japan   Vol. 61 ( 0 )   2014

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    In order to reconstruct past change in hydroclimate at humid and warm Japan using tree-ring &delta;18O, we measured several tree ring samples growing from 1751 to 1998 at Kamegamori Mountain in Shikoku, southwestern Japan. The tree-ring &delta;18O chronology covering last two and a half centuries was derived from 6 living fir (Abies homolepis) trees and examined on its climate sensitivity by correlation analysis using instrumentally observed datasets on monthly average temperature, precipitation and relative humidity in Shikoku as well as for the nearest grid point of CRU TS3.21 dataset. The tree-ring cellulose &delta;18O was negatively correlated with the summer precipitation and relative humidity. The spatial correlations indicated the moisture source in the study region originates from the south, suggesting that the tree-ring oxygen isotope values are controlled by the moisture source and by transport processes. The tree-ring &delta;18O chronologies during the 248 years are consistent with extreme climate events recorded by some historical documents and meteorological records, such that the low &delta;18O years are corresponding to the years of long-term stagnant Baiu front conditions and/or large-scale typhoon occurrences. This tight relationship indicates that tree-ring &delta;18O in southwest Japan can be used as proxy of extreme climate events.

    DOI: 10.14862/geochemproc.61.0_190

  44. Oxygen isotopes as a valuable tool for measuring annual growth in tropical trees that lack distinct annual rings Reviewed

    Chenxi Xu, Masaki Sano, Kei Yoshimura, Takeshi Nakatsuka

    GEOCHEMICAL JOURNAL   Vol. 48 ( 4 ) page: 371 - 378   2014

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    Some trees from tropical areas lack visually detectable and consistent annual growth rings. As such, we have measured the radial variation of cellulose oxygen isotopes in trees that grow in seasonally dry forests of Northern Laos to explore the possibility if this method can be used for the identification of annual rings. One disk from a 7-year-old Styrax tonkinensis (S. tonkinensis) in plantation and two cores from two Ficus semicordata var. semicordata (F. semicordata) in forests were examined. High-resolution cellulose oxygen isotopes of S. tonkinensis and F. semicordata show clear cycles with amplitudes of 5 parts per thousand and 9 parts per thousand, respectively. To further test if the oxygen isotope cycles that we observed are annual or not, a tree ring cellulose oxygen isotope model is employed. Input data of the model are relative humidity and modeled precipitation delta O-18. The modeling results independently support our detection of oxygen isotope annual cycles. Therefore, we conclude that tree ring cellulose oxygen isotopes have great potential to identify annual rings in tropical trees, which typically lack distinct annual rings in the context of seasonal climate.

    DOI: 10.2343/geochemj.2.0312

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  45. Oxygen isotope signatures preserved in tree ring cellulose as a proxy for April-September precipitation in Fujian, the subtropical region of southeast China Reviewed

    Chenxi Xu, Huaizhou Zheng, Takeshi Nakatsuka, Masaki Sano

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   Vol. 118 ( 23 ) page: 12805 - 12815   2013.12

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    A tree ring cellulose oxygen isotope (O-18) chronology for the period 1870-2011 was established using samples from four Fokienia hodginsii trees with the aim of exploring the potential to use tree ring O-18 records to reconstruct climatic variations in Fujian, a subtropical region of southeast China. We believe that this is the first tree ring O-18 chronology from this area. Response analysis revealed that tree ring O-18 is significantly correlated with precipitation between April and September, relative humidity between August and October, and the Palmer drought severity index between April and October. Our O-18 chronology accounts for 37.4% (24.6%) of actual variation in precipitation between April and September during the period from 1951 to 2011 (1901 to 2011). Spatial correlation analysis revealed that tree ring cellulose O-18 is a suitable proxy for reconstructing April-September precipitation in Fujian, as well as in parts of Guangdong and Jiangxi, southeast China. In addition, significant correlations between O-18 chronology and the Indian summer monsoon index show that large-scale atmosphere circulation also influences tree ring O-18. Comparisons between the tropical Pacific sea surface temperature (SST) and tree ring O-18, during the period from 1895 to 2009, indicate that the tropical Pacific SST is positively correlated with tree ring O-18 in the study region over the last 110years, except between 1920 and 1960. Reduced El Nino-Southern Oscillation (ENSO) variance from 1920 to 1960 may result in collapsed relationship between tree ring O-18 in Fujian and tropical Pacific SST.

    DOI: 10.1002/2013JD019803

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  46. Tree-ring reconstructed summer temperature anomalies for temperate East Asia since 800 CE Reviewed

    Edward R. Cook, Paul J. Krusic, Kevin J. Anchukaitis, Brendan M. Buckley, Takeshi Nakatsuka, Masaki Sano

    CLIMATE DYNAMICS   Vol. 41 ( 11-12 ) page: 2957 - 2972   2013.12

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    We develop a summer temperature reconstruction for temperate East Asia based on a network of annual tree-ring chronologies covering the period 800-1989 C.E. The East Asia reconstruction is the regional average of 585 individual grid point summer temperature reconstructions produced using an ensemble version of point-by-point regression. Statistical calibration and validation tests indicate that the regional average possesses sufficient overall skill to allow it to be used to study the causes of temperature variability and change over the region. The reconstruction suggests a moderately warm early medieval epoch (ca. 850-1050 C.E.), followed by generally cooler 'Little Ice Age' conditions (ca. 1350-1880 C.E.) and 20th century warming up to the present time. Since 1990, average temperature has exceeded past warm epochs of comparable duration, but it is not statistically unprecedented. Superposed epoch analysis reveals a volcanic forcing signal in the East Asia summer temperature reconstruction, resulting in pulses of cooler summer conditions that may persist for several years. Substantial uncertainties remain, however, particularly at lower frequencies, thus requiring caution and scientific prudence in the interpretation of this record.

    DOI: 10.1007/s00382-012-1611-x

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  47. A 400-year record of hydroclimate variability and local ENSO history in northern Southeast Asia inferred from tree-ring delta O-18 Reviewed

    Chenxi Xu, Masaki Sano, Takeshi Nakatsuka

    PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY   Vol. 386   page: 588 - 598   2013.9

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    We present here a chronology of tree ring cellulose delta O-18 for the period 1588-2002 based on individual measurements of seven Fokienia hodginsii trees growing in northern Laos. Response function analysis of meteorological data revealed that this oxygen isotope chronology has a significant negative correlation with monsoon season precipitation, the water level of the Mekong River, and the Palmer drought severity index (PDSI). Our reconstructed monsoon season PDSI, which accounts for 41.5% of PDSI variance, showed that wetter phases occurred during the periods AD 1660-1695 and AD 1705-1790, that the main drier periods were AD 1630-1660, AD 1900-1940, and AD 1954-2002, and that there has been a trend of decreasing moisture during the monsoon season over the last 200 years. A reduction in monsoon activity can also be seen in various tree ring oxygen isotope records from the Himalaya, Tibet Plateau, and Southeast Asia. Rising sea surface temperatures over the tropical Pacific and Indian Ocean could be responsible for this reduction in the Asian summer monsoon. By combining proxies sensitive to the El Nino-Southern Oscillation (ENSO) in northern Laos and Vietnam, we were able to reconstruct the annual multivariate ENSO index (MEI) and local ENSO event history, and so improve our understanding of long-term variations in ENSO and its influences on Southeast Asia. (C) 2013 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.palaeo.2013.06.025

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  48. May-September precipitation in the Bhutan Himalaya since 1743 as reconstructed from tree ring cellulose O-18 Reviewed

    Masaki Sano, Phuntsho Tshering, Jiro Komori, Koji Fujita, Chenxi Xu, Takeshi Nakatsuka

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   Vol. 118 ( 15 ) page: 8399 - 8410   2013.8

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:AMER GEOPHYSICAL UNION  

    We developed a 50-year tree ring O-18 chronology for each of three tree species (Juniperus indica, Larix griffithii, and Picea spinulosa) using a total of 12 trees (four trees per species) from the Bhutan Himalaya. Despite originating from different species sampled at two different altitudes, the O-18 chronologies are highly correlated with one another (r=0.76-0.89). Response analyses reveal that tree ring O-18 values are controlled mainly by summer precipitation, irrespective of species. Based on these results, a robust 269-year O-18 chronology was established to reconstruct the amount of May-September precipitation based on data from four larch trees. Our tree ring O-18 data show significant correlations with those from other regions of the Himalaya and the Tibetan Plateau, indicating that common signals related to monsoon activity are recorded in the data. However, at centennial timescales, our data from Bhutan show normal conditions during the 20th century, whereas records from sites in western Nepal and the southern/eastern Tibetan Plateau show weakening trends in monsoon intensity during the last 100-200years; the weakening trends may be the result of a reduction in the meridional sea surface temperature gradient in the Indian Ocean during this time. At continental scales, the tree ring records show that areas more from ocean basins are particularly sensitive to reduced monsoon circulation. Correlation analyses suggest that the El Nino-Southern Oscillation (ENSO) plays an important role in modulating summer precipitation. However, the teleconnected relationship disappears during the period 1951-1970, coinciding with a negative phase of the Pacific Decadal Oscillation (PDO), implying interdecadal modulation of the PDO on the influence of the ENSO on precipitation in Bhutan.

    DOI: 10.1002/jgrd.50664

    Web of Science

    Scopus

  49. Continental-scale temperature variability during the past two millennia (vol 6, pg 339, 2013) Reviewed

    PAGES, k Consortium

    NATURE GEOSCIENCE   Vol. 6 ( 6 ) page: 339 - 346   2013.6

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    Language:English   Publisher:NATURE PUBLISHING GROUP  

    DOI: 10.1038/ngeo1834

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  50. Continental-scale temperature variability during the past two millennia

    Ahmed Moinuddin, Anchukaitis Kevin J., Asrat Asfawossen, Borgaonkar Hemant P., Braida Martina, Buckley Brendan M., Buntgen Ulf, Chase Brian M., Christie Duncan A., Cook Edward R., Curran Mark A. J., Diaz Henry F., Esper Jan, Fan Ze-Xin, Gaire Narayan P., Ge Quansheng, Gergis Joelle, Gonzalez-Rouco J. Fidel, Goosse Hugues, Grab Stefan W., Graham Nicholas, Graham Rochelle, Grosjean Martin, Hanhijarvi Sami T., Kaufman Darrell S., Kiefer Thorsten, Kimura Katsuhiko, Korhola Atte A., Krusic Paul J., Lara Antonio, Lezine Anne-Marie, Ljungqvist Fredrik C., Lorrey Andrew M., Luterbacher Jurg, Masson-Delmotte Valerie, McCarroll Danny, McConnell Joseph R., McKay Nicholas P., Morales Mariano S., Moy Andrew D., Mulvaney Robert, Mundo Ignacio A., Nakatsuka Takeshi, Nash David J., Neukom Raphael, Nicholson Sharon E., Oerter Hans, Palmer Jonathan G., Phipps Steven J., Prieto Maria R., Rivera Andres, Sano Masaki, Severi Mirko, Shanahan Timothy M., Shao Xuemei, Shi Feng, Sigl Michael, Smerdon Jason E., Solomina Olga N., Steig Eric J., Stenni Barbara, Thamban Meloth, Trouet Valerie, Turney Chris S. M., Umer Mohammed, van Ommen Tas, Verschuren Dirk, Viau Andre E., Villalba Ricardo, Vinther Bo M., von Gunten Lucien, Wagner Sebastian, Wahl Eugene R., Wanner Heinz, Werner Johannes P., White James W. C., Yasue Koh, Zorita Eduardo

    NATURE GEOSCIENCE   Vol. 6 ( 5 ) page: 339 - 346   2013.5

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    Language:Japanese   Publisher:Nature Geoscience  

    Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between ad 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period ad 1971-2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years.

    DOI: 10.1038/NGEO1797

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    Scopus

  51. Increasing aridity over the past 223 years in the Nepal Himalaya inferred from a tree-ring delta O-18 chronology Reviewed

    Masaki Sano, R. Ramesh, M. S. Sheshshayee, R. Sukumar

    HOLOCENE   Vol. 22 ( 7 ) page: 809 - 817   2012.7

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:SAGE PUBLICATIONS LTD  

    A tree-ring delta O-18 chronology of Abies spectabilis from the Nepal Himalaya was established to study hydroclimate in the summer monsoon season over the past 223 years (AD 1778-2000). Response function analysis with ambient climatic records revealed that tree-ring delta O-18 was primarily controlled by the amount of precipitation and relative humidity during the monsoon season (June-September). Since tree-ring delta O-18 was simultaneously correlated with temperature, drought history in the monsoon season was reconstructed by calibrating against the Palmer Drought Severity Index (PDSI). Our reconstruction that accounts for 33.7% of the PDSI variance shows a decreasing trend of precipitation/moisture over the past two centuries, and reduction of monsoon activity can be found across different proxy records from the Himalaya and Tibet. Spatial correlation analysis with global sea surface temperatures suggests that the tropical oceans play a role in modulating hydroclimate in the Nepal Himalaya. Although the dynamic mechanisms of the weakening trend of monsoon intensity still remain to be analyzed, rising sea surface temperatures over the tropical Pacific and Indian Ocean could be responsible for the reduction of summer monsoon.

    DOI: 10.1177/0959683611430338

    Web of Science

  52. A 300-year Vietnam hydroclimate and ENSO variability record reconstructed from tree ring delta O-18 Reviewed

    Masaki Sano, Chenxi Xu, Takeshi Nakatsuka

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   Vol. 117 ( D12115 )   2012.6

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:AMER GEOPHYSICAL UNION  

    A tree ring delta O-18 chronology is developed for the past 300 years (1705-2004) using 6 cypress trees from northern Vietnam to reconstruct long-term hydroclimatic variations in the summer monsoon season. To the best of our knowledge, this is the first well-replicated tree ring delta O-18 chronology from Southeast Asia, as well as the longest yet produced. Response analyses reveal that tree ring delta O-18 is significantly correlated with temperature, precipitation, and the Palmer Drought Severity Index (PDSI) during the period May-October, with highest correlation to the PDSI. Our delta O-18 chronology accounts for 44% of the PDSI variance, and is in good agreement with a 52-year tree ring delta O-18 chronology from northern Laos (r = 0.77), indicating that regional hydroclimatic signals are well recorded in the delta O-18 data. Spatial correlation analyses with global sea surface temperatures suggest that the tropical Pacific plays an important role in modulating hydroclimate over the study region. Further, the delta O-18 chronology correlates significantly with El Nino-Southern Oscillation (ENSO)-related indices, and is therefore used to reconstruct the annual Multivariate ENSO Index. Because previously published ENSO reconstructions are based mainly on proxy records originating from North America and/or the tropical Pacific, the future development of a tree ring delta O-18 network from mainland Southeast Asia could lead to an independent and more robust reconstruction of ENSO variability.

    DOI: 10.1029/2012JD017749

    Web of Science

    Scopus

  53. Tree ring cellulose delta O-18 of Fokienia hodginsii in northern Laos: A promising proxy to reconstruct ENSO? Reviewed

    Chenxi Xu, Masaki Sano, Takeshi Nakatsuka

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   Vol. 116 ( D24109 )   2011.12

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:AMER GEOPHYSICAL UNION  

    A tree ring cellulose delta O-18 chronology of Fokienia hodginsii from 1951 to 2002 is established by four cores from four different trees to explore its potential for reconstructing climatic variations in northern Laos. This chronology is the first tree ring delta O-18 chronology from Laos as well as the first for this species. We compare variations of tree ring cellulose delta O-18 and ring width between cores. The results suggest that the delta O-18 time series are more strongly correlated between different trees than ring width time series are. In addition, correlation analysis shows a significantly negative correlation between tree ring cellulose delta O-18 and the May-October Palmer Drought Severity Index (PDSI), while the tree ring width indices have a poor correlation with PDSI. The spatial correlation analysis between tree ring cellulose delta O-18 and global sea surface temperature and the time series correlation analysis between tree ring cellulose delta O-18 and the Multivariate El Nino-Southern Oscillation (ENSO) Index (MEI) during the investigated period (1951-2002) reveal that ENSO has an important effect on tree ring cellulose delta O-18 in Laos. Our results indicate that the tree ring cellulose delta O-18 of Fokienia hodginsii is a promising proxy to reconstruct PDSI in Southeast Asian countries, such as Laos, and to discuss their teleconnections with global atmospheric circulations such as ENSO.

    DOI: 10.1029/2011JD016694

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    Scopus

  54. Summer temperature variations in southern Kamchatka as reconstructed from a 247-year tree-ring chronology of Betula ermanii Reviewed

    Masaki Sano, Fumito Furuta, Tatsuo Sweda

    JOURNAL OF FOREST RESEARCH   Vol. 15 ( 4 ) page: 234 - 240   2010.8

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER JAPAN KK  

    We have developed a 247-year ring-width chronology of Betura ermanii Cham. growing in an open canopy forest close to the tree line at a coastal site in southern Kamchatka. Climatic response analyses revealed that the ring width was primarily controlled by July-August temperature. The regression models that we used for statistical reconstruction passed the stringent calibration-verification tests used in dendroclimatology, resulting in the first quality-controlled tree-ring reconstruction for southern Kamchatka. The reconstructed temperature shows a cool period from the 1830s to the 1880s, followed by gradual warming until ca. 1940, then a cooling trend extending to the 1970s, and finally a warming trend continuing to the present. Spatial correlation analyses with sea surface temperature in the North Pacific indicated that the seas surrounding the Kamchatka peninsula play a role in modulating temperature variations in the study area whereas the effects of the Pacific Decadal Oscillation are relatively weak.

    DOI: 10.1007/s10310-010-0183-z

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    Scopus

  55. Climate as a contributing factor in the demise of Angkor, Cambodia Reviewed

    Brendan M. Buckley, Kevin J. Anchukaitis, Daniel Penny, Roland Fletcher, Edward R. Cook, Masaki Sano, Le Canh Nam, Aroonrut Wichienkeeo, Ton That Minh, Truong Mai Hong

    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA   Vol. 107 ( 15 ) page: 6748 - 6752   2010.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATL ACAD SCIENCES  

    The "hydraulic city" of Angkor, the capitol of the Khmer Empire in Cambodia, experienced decades-long drought interspersed with intense monsoons in the fourteenth and fifteenth centuries that, in combination with other factors, contributed to its eventual demise. The climatic evidence comes from a seven-and-a-half century robust hydroclimate reconstruction from tropical southern Vietnamese tree rings. The Angkor droughts were of a duration and severity that would have impacted the sprawling city's water supply and agricultural productivity, while high-magnitude monsoon years damaged its water control infrastructure. Hydroclimate variability for this region is strongly and inversely correlated with tropical Pacific sea surface temperature, indicating that a warm Pacific and El Nino events induce drought at interannual and interdecadal time scales, and that low-frequency variations of tropical Pacific climate can exert significant influence over Southeast Asian climate and society.

    DOI: 10.1073/pnas.0910827107

    Web of Science

    PubMed

  56. Climatic potential of delta O-18 of Abies spectabilis from the Nepal Himalaya Reviewed

    Masaki Sano, M. S. Sheshshayee, S. Managave, R. Ramesh, R. Sukumar, Tatsuo Sweda

    DENDROCHRONOLOGIA   Vol. 28 ( 2 ) page: 93 - 98   2010

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER GMBH, URBAN & FISCHER VERLAG  

    A 50-year tree-ring delta O-18 chronology of Abies spectabilis growing close to the tree line (3850 m asl) in the Nepal Himalaya is established to explore its dendroclimatic potential. Response function analysis with ambient climatic records revealed that tree-ring delta O-18 is primarily governed by rainfall during the monsoon season (June September), and the regression model accounts for 35% of the variance in rainfall. Extreme dry years identified in instrumental weather data are detected in the delta O-18 chronology. Further, tree-ring delta O-18 is much more sensitive to rainfall fluctuations than other tree-ring parameters such as width and density typically used in dendroclimatology. Correlation analyses with Nino 3.4 SST reveal time-dependent behavior of ENSO-monsoon relationships. (C) 2009 Elsevier GmbH. All rights reserved.

    DOI: 10.1016/j.dendro.2009.05.005

    Web of Science

  57. Tree-ring based hydroclimate reconstruction over northern Vietnam from Fokienia hodginsii: eighteenth century mega-drought and tropical Pacific influence Reviewed

    Masaki Sano, Brendan M. Buckley, Tatsuo Sweda

    CLIMATE DYNAMICS   Vol. 33 ( 2-3 ) page: 331 - 340   2009.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER  

    We present here the first statistically calibrated and verified tree-ring reconstruction of climate from continental Southeast Asia. The reconstructed variable is March-May (MAM) Palmer Drought Severity Index (PDSI) based on ring widths from 22 trees (42 radial cores) of rare and long-lived conifer, Fokienia hodginsii (Po Mu as locally called) from northern Vietnam. This is the first published tree ring chronology from Vietnam as well as the first for this species. Spanning 535 years, this is the longest cross-dated tree-ring series yet produced from continental Southeast Asia. Response analysis revealed that the annual growth of Fokienia at this site was mostly governed by soil moisture in the pre-monsoon season. The reconstruction passed the calibration-verification tests commonly used in dendroclimatology, and revealed two prominent periods of drought in the mid-eighteenth and late-nineteenth centuries. The former lasted nearly 30 years and was concurrent with a similar drought over northwestern Thailand inferred from teak rings, suggesting a "mega-drought" extending across Indochina in the eighteenth century. Both of our reconstructed droughts are consistent with the periods of warm sea surface temperature (SST) anomalies in the tropical Pacific. Spatial correlation analyses with global SST indicated that ENSO-like anomalies might play a role in modulating droughts over the region, with El Nio (warm) phases resulting in reduced rainfall. However, significant correlation was also seen with SST over the Indian Ocean and the north Pacific, suggesting that ENSO is not the only factor affecting the climate of the area. Spectral analyses revealed significant peaks in the range of 53.9-78.8 years as well as in the ENSO-variability range of 2.0 to 3.2 years.

    DOI: 10.1007/s00382-008-0454-y

    Web of Science

  58. Tree-ring-width chronology of Larix gmelinii as an indicator of changes in early summer temperature in east-central Kamchatka Reviewed

    Masaki Sano, Fumito Furuta, Tatsuo Sweda

    JOURNAL OF FOREST RESEARCH   Vol. 14 ( 3 ) page: 147 - 154   2009.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER TOKYO  

    We developed a 378-year tree-ring-width chronology based on 110 core samples from 55 individual trees of Larix gmelinii (Rupr.) Rupr. growing in a wide open forest close to the tree line in the Kronotsky National Park. Reflecting strong climatic control over tree growth not only within the study area but also more extensively over central Kamchatka, our chronology was well correlated with those from other larch sites. Response analysis with 10-day mean temperature revealed that the ring width was primarily controlled by the temperature of early summer, i.e., of late May through late June (40 days). While the regression models for a formal reconstruction failed to pass stringent verification tests commonly used in dendroclimatology, the relationship between tree growth and climate was statistically significant and credible. We therefore used our chronology as a proxy of early summer temperature. The chronology shows a cool period from the 1660s until the 1680s, followed by gradual warming until ca. 1800, then by a slight cooling trend extending to ca. 1910, and a warming trend continuing up to the present, with decadal fluctuations throughout the chronology. The warming trend found in our chronology over the twentieth century is generally consistent with the ones commonly appearing in higher latitudes.

    DOI: 10.1007/s10310-009-0123-y

    Web of Science

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Books 2

  1. 新しい気候観と日本史の新たな可能性

    中塚 武, 鎌谷 かおる, 佐野 雅規, 伊藤 啓介(日本史), 對馬 あかね

    臨川書店  2021  ( ISBN:9784653045014

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    Language:Japanese

    CiNii Books

  2. 古気候の復元と年代論の構築

    中塚 武, 對馬 あかね, 佐野 雅規

    臨川書店  2021  ( ISBN:9784653045021

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    Language:Japanese

    CiNii Books

MISC 4

  1. Analysis of occurrence history of landslides using dead plants: stable isotope dendrochronology for buried logs in natural dams and radiocarbon dating for pond sediments in a landslide mass

    Yamada, R, Iida, T, Wakatsuki, T, Kimura, T, Kariya, Y, Sano, M, Li, Z, Tsushima, A, Nakatsuka, T

    Fission Track News Letter   ( 30 ) page: 23 - 24   2017.12

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    Language:Japanese   Publishing type:Rapid communication, short report, research note, etc. (bulletin of university, research institution)  

  2. Climate response of oxygen isotopic compositions in tree-ring cellulose from Java, Indonesia: consideration based on proxy system model Reviewed

    Hisamochi, R, Watanabe, Y, Kurita, N, Sano, M, Nakatsuka, T, Matsuo, M, Yamamoto, H, Sugiyama, J, Tusda, T, Tagami, T

    JpGU-AGU Joint Meeting 2017     2017

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    Language:English  

  3. Comparison of tree-ring δ 18O and meteorological data from Java island, Indonesia Reviewed

    Watanabe, Y, Hisamochi, R, Sano, M, Nakatsuka, T, Tazuru, S, Sugiyama, J, Tsuda, T, Tagami, T

    American Geophysical Union Fall Meeting     2016

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    Language:English  

  4. Estimation of oxygen isotope in source water of tree-ring cellulose in Indonesia using tree-ring oxygen isotope model Reviewed

    Hisamochi, R, Watanabe, Y, Kurita, N, Sano, M, Nakatsuka, T, Sugiyama, J, Tusda, T, Tagami, T

    American Geophysical Union Fall Meeting     2016

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    Language:English  

KAKENHI (Grants-in-Aid for Scientific Research) 21

  1. Dendrochronological study for precise chronology of the past 30,000 years of extreme climate and disaster history

    Grant number:20H00035  2020.4 - 2025.3

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    Authorship:Coinvestigator(s) 

  2. Dendrochronological study for precise chronology of the past 30,000 years of extreme climate and disaster history

    2020.4 - 2025.3

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    Grant type:Competitive

  3. 東アジア産木材の年代決定と産地判別を可能にする年輪酸素同位体比データベースの構築

    Grant number:20H01373  2020.4 - 2023.3

    科学研究費助成事業  基盤研究(B)

    佐野 雅規, 安江 恒, 箱崎 真隆, 香川 聡, 大橋 伸太, 酒井 武

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    Authorship:Principal investigator 

    Grant amount:\17810000 ( Direct Cost: \13700000 、 Indirect Cost:\4110000 )

    これまで我々は、樹木年輪の同位体比に基づく高精度な(1)年代測定法と(2)木材産地判別法を独自に考案し、(3)高効率な同位体分析法の開発を成し遂げてきた。さらに近年、現生木や考古材から迅速かつ簡単に年輪コアサンプル採取を可能にする(4)年輪コア自動採取装置を開発した。本研究では、これまで蓄積してきた知見や技術を最大限に活用し、東アジア各地においける年輪酸素同位体比データの構築を通じて、木材の年代測定と産地判別の技術基盤を形成する。本研究は、文化財科学への貢献にくわえ、木材の違法伐採という現在の社会問題の解決にも資する。

  4. 東アジア産木材の年代決定と産地判別を可能にする年輪酸素同位体比データベースの構築

    2020.4 - 2021.3

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    Grant type:Competitive

    これまで我々は、樹木年輪の同位体比に基づく高精度な(1)年代測定法と(2)木材産地判別法を独自に考案し、(3)高効率な同位体分析法の開発を成し遂げてきた。さらに近年、現生木や考古材から迅速かつ簡単に年輪コアサンプル採取を可能にする(4)年輪コア自動採取装置を開発した。本研究では、これまで蓄積してきた知見や技術を最大限に活用し、東アジア各地においける年輪酸素同位体比データの構築を通じて、木材の年代測定と産地判別の技術基盤を形成する。本研究は、文化財科学への貢献にくわえ、木材の違法伐採という現在の社会問題の解決にも資する

  5. Study of Reconstruction of Archaeological dating and Process of Cultural and Ecological History in East Asia in the Neolithic period

    Grant number:18H00744  2018.4 - 2023.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Authorship:Coinvestigator(s) 

  6. Study of Reconstruction of Archaeological dating and Process of Cultural and Ecological History in East Asia in the Neolithic period

    2018.4 - 2023.3

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    Grant type:Competitive

  7. Integrating paleoclimate data with rice yields estimated from historical documents during the early modern period in Japan

    Grant number:17K18517  2017.6 - 2020.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Challenging Research (Exploratory)

    Sano Masaki

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    Authorship:Principal investigator 

    Grant amount:\6370000 ( Direct Cost: \4900000 、 Indirect Cost:\1470000 )

    This study was conducted to reveal the effect of climate changes on rice yields during the early modern period in Japan. Overall, rice yields inferred from historical documents were shown to be controlled by early summer precipitation reconstructed from oxygen isotopes in tree rings. In addition, the methodology of tax calculation changed spatially and temporally over the early modern period, indicating sociological diversity of the local governments in accordance with changes of the relationship between climate and rice productivity.

  8. Integrating paleoclimate data with rice yields estimated from historical documents during the early modern period in Japan

    2017.6 - 2019.3

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    Grant type:Competitive

  9. Reorganization of prehistorical structure of calendar age and evaluation of climate change effect in Japanese archipelago using tree ring oxygen isotope ratios

    Grant number:17H06118  2017.5 - 2022.3

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    Authorship:Coinvestigator(s) 

  10. Reorganization of prehistorical structure of calendar age and evaluation of climate change effect in Japanese archipelago using tree ring oxygen isotope ratios

    2017.5 - 2022.3

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    Grant type:Competitive

  11. 樹木年輪とアイスコアの統合解析によるアジア山岳域の標高別古気候復元

    Grant number:17H01621  2017.4 - 2021.3

    科学研究費助成事業  基盤研究(A)

    佐野 雅規, 藤田 耕史, 對馬 あかね

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    Authorship:Principal investigator 

    Grant amount:\41730000 ( Direct Cost: \32100000 、 Indirect Cost:\9630000 )

    本研究の目的は、アジア(ヒマラヤ)の山岳域において樹木年輪とアイスコアを併用して、低標高から高度6000m付近に至る広高度帯で気候復元を行い、気候変動の高度依存性を解明することである。今年度は、ネパール東部のマカルーで新たに年輪サンプルを収集した。過去3年間のフィールドワークによって、ネパールヒマラヤの西部、中部、東部をカバーする計4地域から、標高1800-3900mの高度帯で年輪サンプルを取得するに至った。樹木の生育環境や樹種の特性によって、採取した年輪サンプルから過去に遡及できる期間が200-400年となっている。持ち帰ったサンプルは、各地域で4-5個体を対象とし、その年輪セルロースの酸素同位体比を個体別に1年単位でそれぞれ測定して時系列データを取得した。また昨年度に引き続き、共同研究の推進と分析技術の移転のため、ネパールの研究者を約3週間にわたって日本に招聘してデータの収集を進めた。一方、本年度は、もうひとつの分析対象であるアイスコアの掘削に集中的に取り組んだ。過去2年間の経験を踏まえ、十分に準備を整えたうえで、2019年10-11月にネパールヒマラヤのトランバウ氷河においてアイスコアを掘削した。その結果、当初の計画通り標高約6000m地点にて、81.2m長のアイスコアを採取することに成功した。2017年度と2018年度の試掘削で採取したアイスコアの解析結果から、今年度に採取した81.2mのアイスコアから、過去160年超に遡って気候・環境変動を復元できる見通しが得られた。また、アイスコアには全体の12.9%を占める層で多数のダストが存在した。深層部(70m以深)では中層部(40-50m深)に比べダスト層が多く存在し、その粒子径も中層部に比べて大きいことが確認できた。この結果は、時代により掘削地点へのダストの輸送量や輸送起源が変化している可能性を示唆している。
    過去3年におよぶネパールでの年輪調査は順調に進み、当初の予定よりも多くの地域で年輪サンプルを採取することができた。年輪サンプルの酸素同位体比データの取得についても、既に2地域で測定が完了しており、残りのサンプルについても2020年度中に測定できるよう処理を進めている。アイスコアについても2019年度に実施した本掘削が成功し、長さ80m超の良質なサンプルを収集できた。初期分析の結果、アイスコアの平均密度は866kg/m3で、仮に830kg/m3を氷化密度とした場合、深さ約12m地点から氷化していること、アイスコア全体の約87.9%を氷で占めていることがわかった。
    樹木年輪については、残っているサンプルの酸素同位体比の測定を進め、標高別、地域別に気候を過去200-400年間にわたって復元して、気候変動の標高依存性や地域特性を明らかにする。アイスコアについては、水の安定同位体比や化学主成分、および鉛同位体比などの人為起源の大気汚物質を測定する。次いで、高度6000m地点における過去200年弱の降水量変動を含めた古環境変動の復元を行うとともに、人間活動と気候変動の関係についても考察する。また、最終目標として掲げた、気候変動の高度依存性を明らかにするため、高度6000mのアイスコアの記録と、異標高で採取された年輪試料の記録の比較解析を行う。

  12. 樹木年輪とアイスコアの統合解析によるアジア山岳域の標高別古気候復元

    2017.4 - 2021.3

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    Grant type:Competitive

    本研究の目的は、アジアの山岳域において樹木年輪と山岳アイスコアを併用して、低標高から高度6000m付近に至る広高度帯で気候復元を行い、気候変動の高度依存性を解明することである。今年度は、ランタン(ネパール中部)とカプタッド(ネパール西部)において、標高1800mから3850mに至る高度帯にて、多数の針葉樹から樹木年輪サンプルを採取した。持ち帰ったコア試料の年輪数から、過去400年超の気候変動を復元できる見通しが立った。そこで、収集したサンプル群の中から、遡及期間の長さ、採取した高度、年輪分析の難度を総合的に検討し、以後の分析に使用するサンプルの優先順位を決定した。この基準に基づき、過去400年超の年輪酸素同位体比データを構築するために、セルロースの抽出や年輪サンプルの切分け、同位体比質量分析計での酸素同位体比の測定を進めた。昨年度に取得したサンプルも含めて、合計で3つの地域からサンプルを収集できており、過去100-200年間については分析が完了している。また、分析技術を海外に移転させるため、ネパールの研究者を約3週間にわたって日本に招聘して実習とデータの収集を進めた。一方、もうひとつの分析対象であるアイスコアについては、昨年度の経験を踏まえ、ロールワリンのトランバウ氷河にて再度アイスコアの仮掘削を実施して、長さ8mに達するコアを採取することに成功した。アイスコアは現場にてダスト層と氷板の目視観測および密度を算出するための長さと重量の測定を行った後、化学主成分の測定に適した処理を施し日本に持ち帰った。アイスコアの水安定同位体比と化学主成分を分析した結果、トランバウ氷河標高5800m付近の年間の涵養量は水換算で0.50-0.86m程度であると見積もられた。次年度に100mのアイスコアを掘削できれば、200年にわたる過去の環境変動を復元できる可能性があることがわかった。ネパールでの年輪調査は、予定よりも多くの地点でサンプルを採取することができた。また、持ち帰ったサンプルについても、優先順位を明確にさせたうえで、計画通り分析が進んでいる。他方、アイスコアについては、改めて実施した仮掘削によって長さ8mのサンプルを収集するに至った。今年度は、過去2年間で取得した2つのアイスコアについて酸素同位体比および化学主成分の測定を行ない、アイスコアから掘削地点の年間の涵養量を推定した。樹木年輪サンプルの収集は過去2年で大幅に進んだので、今年度は、酸素同位体比の計測による年輪データの取得に集中する。次いで、アイスコアとの比較を見据え、まずは樹木年輪の酸素同位体比データのみを用いて、過去の気候変動の時間・空間分布と、気候変動の高度依存性を明らかにする。また、2019年度の最大の目標は、高度6000m地点で100mの長いアイスコアを採取することであり、そのための各種の準備を2018年度から進めきた。この掘削で採取されたコアサンプルを用いて各種の化学分析の分析を行うことで、過去約200年間にわたる高標高域の古気候復元が可能となる。樹木年輪データとアイスコアデータを統合して、気候変動の高度依存性を明らかにする

  13. Developing a network of tree-ring oxygen isotope chronologies over Japan, Korea and Taiwan, for precisely dating archeological woods

    Grant number:17H02020  2017.4 - 2020.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    Sano Masaki

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    Authorship:Principal investigator 

    Grant amount:\17030000 ( Direct Cost: \13100000 、 Indirect Cost:\3930000 )

    A tree-ring network of oxygen isotope chronologies was developed for Japan, Taiwan and Korea, in order to precisely date archeological wooden samples. Archeological samples originating in Korea were successfully dated using regional tree-ring chronologies established using wood samples from Japan. Also, tree-ring data from China were shown to be well matched with those from Taiwan. Overall, the newly developed tree-ring dataset made it possible to date wooden samples originating from East Asia. It should be also noted that the state-of-the-art technology of isotope dendrochronology was successfully transferred to researchers in Korea and Taiwan, leading to active collaboration with them.

  14. Developing a network of tree-ring oxygen isotope chronologies over Japan, Korea and Taiwan, for precisely dating archeological woods

    2017.4 - 2020.3

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    Grant type:Competitive

  15. Reconstruction of calendar framework and evaluation of climatic impact on prehistorical Japanese archipelago using tree-ring oxygen isotope ratio

    Grant number:17H00943  2017.4 - 2018.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (A)

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    Authorship:Coinvestigator(s) 

  16. Variations in summer monsoon intensity over the past 2000 years in southwestern Japan, as reconstructed from tree-ring oxygen isotopes

    Grant number:26740008  2014.4 - 2017.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists (B)

    Sano Masaki

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    Authorship:Principal investigator 

    Grant amount:\3900000 ( Direct Cost: \3000000 、 Indirect Cost:\900000 )

    A total of 21 core samples collected from living and dead trees of Japanese ceder in Yakushima Island were used to construct a 1772-year tree-ring oxygen isotope chronology. Response analysis with ambient meteorological stations indicated that the oxygen isotope ratios of this chronology were significantly and negatively correlated with relative humidity and amounts of precipitation. Overall, a relatively dry (wet) condition was found in the Medieval Warm Period (the Little Ice Age). In addition, a notable drying trend was identified in the 20th century.

  17. Variations in summer monsoon intensity over the past 2000 years in southwestern Japan, as reconstructed from tree-ring oxygen isotopes

    2014.4 - 2017.3

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    Grant type:Competitive

    A total of 21 core samples collected from living and dead trees of Japanese ceder in Yakushima Island were used to construct a 1772-year tree-ring oxygen isotope chronology. Response analysis with ambient meteorological stations indicated that the oxygen isotope ratios of this chronology were significantly and negatively correlated with relative humidity and amounts of precipitation. Overall, a relatively dry (wet) condition was found in the Medieval Warm Period (the Little Ice Age). In addition, a notable drying trend was identified in the 20th century

  18. 樹木年輪の酸素同位体比を用いた東南アジア大陸部における気候の精密復元

    Grant number:23710006  2011.4 - 2012.3

    科学研究費助成事業  若手研究(B)

    佐野 雅規

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    Authorship:Principal investigator 

    Grant amount:\4420000 ( Direct Cost: \3400000 、 Indirect Cost:\1020000 )

  19. 樹木年輪の酸素同位体比を用いた東南アジア大陸部における気候の精密復元

    2011.4 - 2012.3

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    Grant type:Competitive

  20. 樹木年輪セルロースの酸素同位体比によるインドシナ半島の古気候復元

    Grant number:22880015  2010 - 2011

    科学研究費助成事業  研究活動スタート支援

    佐野 雅規

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    Authorship:Principal investigator 

    Grant amount:\2327000 ( Direct Cost: \1790000 、 Indirect Cost:\537000 )

    ベトナムとラオスの国境を成すアンナン山脈を対象とし、現地での聞き取り調査からフォッキニア(ラオスヒノキ)の大径木の分布域を把握したうえで、実際にそれらの地域にて老齢木を探索した結果、3地域の天然林から合計92個体306コアの年輪サンプルを採取することができた。持ち帰ったサンプルの観察から、年輪幅変動の個体間での共通性が乏しく、それゆえ、変動パターンの個体間比較による年輪年代の照合が困難であった。これは、隣接木との競合による生態的な要因が肥大成長を大きく左右するためで、既往の研究から予測しうる結果であった。
    本研究では、生態的な影響を受けず、主に気候を反映している酸素同位体比の変動パターンを多数の個体間で比較することにより年輪年代を決定し、その結果として得られる標準年輪曲線による気候復元を目的としている。そのためには、大量のサンプルからセルロースを迅速に抽出する実験手法の考案が不可欠であり、本年度はその方法を確立した。具体的には、これまで年層を一枚ずつ分離したうえで粉砕し、年層毎に反応管にて化学処理を施しセルロースを抽出していたが、年層の分離前にサンプルを薄板化し、年輪の形状を保ったまま化学処理を行い、板状のままセルロースを抽出した後に年層を切り分ける方法に改め、作業効率を飛躍的に向上させることができた。また、同一サンプルを用いて、酸素同位体比につき従来の方法と比較したところ、絶対値に差があるものの、経年変動パターンは極めてよく合っており、新しい実験方法が、本研究の目的とする気候復元に十分耐えうることが確認できた。

  21. 樹木年輪セルロースの酸素同位体比によるインドシナ半島の古気候復元

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    Grant type:Competitive

    ベトナムとラオスの国境を成すアンナン山脈を対象とし、現地での聞き取り調査からフォッキニア(ラオスヒノキ)の大径木の分布域を把握したうえで、実際にそれらの地域にて老齢木を探索した結果、3地域の天然林から合計92個体306コアの年輪サンプルを採取することができた。持ち帰ったサンプルの観察から、年輪幅変動の個体間での共通性が乏しく、それゆえ、変動パターンの個体間比較による年輪年代の照合が困難であった。これは、隣接木との競合による生態的な要因が肥大成長を大きく左右するためで、既往の研究から予測しうる結果であった。本研究では、生態的な影響を受けず、主に気候を反映している酸素同位体比の変動パターンを多数の個体間で比較することにより年輪年代を決定し、その結果として得られる標準年輪曲線による気候復元を目的としている。そのためには、大量のサンプルからセルロースを迅速に抽出する実験手法の考案が不可欠であり、本年度はその方法を確立した。具体的には、これまで年層を一枚ずつ分離したうえで粉砕し、年層毎に反応管にて化学処理を施しセルロースを抽出していたが、年層の分離前にサンプルを薄板化し、年輪の形状を保ったまま化学処理を行い、板状のままセルロースを抽出した後に年層を切り分ける方法に改め、作業効率を飛躍的に向上させることができた。また、同一サンプルを用いて、酸素同位体比につき従来の方法と比較したところ、絶対値に差があるものの、経年変動パターンは極めてよく合っており、新しい実験方法が、本研究の目的とする気候復元に十分耐えうることが確認できた

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