Moisture source signals preserved in a 242-year tree-ring δ18O chronology in the western Himalaya

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

    Research output: Contribution to journalArticle

    13 Citations (Scopus)

    Abstract

    The oxygen isotope ratio (δ18O) of tree-ring cellulose is known to be a reliable proxy for hydroclimate in monsoon Asia. However, tree-ring δ18O 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 δ18O 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 δ18O 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 δ18O 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 δ18O 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.

    Original languageEnglish
    Pages (from-to)73-82
    Number of pages10
    JournalGlobal and Planetary Change
    Volume157
    DOIs
    Publication statusPublished - 2017 Oct 1

    Fingerprint

    tree ring
    chronology
    monsoon
    moisture
    drought
    summer
    water vapor
    oxygen isotope ratio
    cellulose
    relative humidity
    silver
    sampling
    index
    sea

    Keywords

    • Arabian Sea
    • ENSO
    • Indian summer monsoon
    • Isotope dendroclimatology
    • Moisture source

    ASJC Scopus subject areas

    • Global and Planetary Change
    • Oceanography

    Cite this

    Moisture source signals preserved in a 242-year tree-ring δ18O chronology in the western Himalaya. / Sano, Masaki; Dimri, A. P.; Ramesh, R.; Xu, Chenxi; Li, Zhen; Nakatsuka, Takeshi.

    In: Global and Planetary Change, Vol. 157, 01.10.2017, p. 73-82.

    Research output: Contribution to journalArticle

    Sano, Masaki ; Dimri, A. P. ; Ramesh, R. ; Xu, Chenxi ; Li, Zhen ; Nakatsuka, Takeshi. / Moisture source signals preserved in a 242-year tree-ring δ18O chronology in the western Himalaya. In: Global and Planetary Change. 2017 ; Vol. 157. pp. 73-82.
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    abstract = "The oxygen isotope ratio (δ18O) of tree-ring cellulose is known to be a reliable proxy for hydroclimate in monsoon Asia. However, tree-ring δ18O 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 δ18O 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 δ18O 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 δ18O 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 δ18O 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.",
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    AU - Xu, Chenxi

    AU - Li, Zhen

    AU - Nakatsuka, Takeshi

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