TY  - JOUR
A1  - Brunello, Camilla Francesca
A1  - Andermann, Christoff
A1  - Helle, Gerhard
A1  - Comiti, Francesco
A1  - Tonon, Giustino
A1  - Tiwari, Achyut
A1  - Hovius, Niels
ED  - Vance, D.
T1  - Hydroclimatic seasonality recorded by tree ring delta O-18 signature across a Himalayan altitudinal transect
JF  - Earth & planetary science letters
N2  - Water stable isotope ratios of tropical precipitation predominantly reflect moisture source and precipitation intensity. Trees can incorporate the isotopic signals into annual tree-ring cellulose records, permitting reconstruction of the temporal changes of hydroclimate over decades to millennia. This is especially valuable in the Himalayas where the understanding of monsoon dynamics is limited by the lack of a dense and representative observational network. We have analyzed tree ring delta O-18 records from two distinct physiographic sites along the upper Kali Gandaki valley in the central Nepal Himalayas, representing the wet High-Himalayas and the Trans-Himalayan dryland to the north. Empirical correlations and regression analyses were compared to an in-situ calibrated oxygen isotope fractionation model, exploring the relationships between tree ring delta O-18 and seasonal-mean variability of hydroclimatic forcing at the different locations. For this purpose, gridded precipitation data from the Asian rain gauge dataset APHRODITE, as well as high resolution onsite observations (relative humidity, air temperature, delta O-18 of precipitation and radial tree growth) were used. We found that two distinct sets of meteorological values, reflecting pre-monsoon and monsoon conditions, are needed to reproduce the measured tree ring delta O-18 values from the High-Himalayan site, but that a single set of monsoonal values performs best for the Trans-Himalayan site. We conclude that Trans-Himalayan trees capture long-term changes in strength of the Indian summer monsoon. In contrast, High-Himalayan tree ring delta(18)Orecords a more complex hydro-climatic signal reflecting both pre-monsoon and monsoon seasons with very contrasting isotopic signatures of precipitation. This difference in the two hydroclimatic proxy records offers an opportunity to reconstruct first-order hydroclimate conditions, such as local precipitation rates, and to gain new insights into monsoon timing and seasonal water source determination across the Himalayan orographic region. (C) 2019 Elsevier B.V. All rights reserved.
KW  - Himalayan hydroclimate
KW  - seasonal precipitation
KW  - pre-monsoon
KW  - monsoon onset
KW  - oxygen fractionation model
KW  - dendroclimatology
Y1  - 2019
U6  - https://doi.org/10.1016/j.epsl.2019.04.030
SN  - 0012-821X
SN  - 1385-013X
VL  - 518
SP  - 148
EP  - 159
PB  - Elsevier
CY  - Amsterdam
ER  -