A precipitation isotopic response in 2014-2015 to moisture transport changes in the central Himalayas

Abstract

The effect of moisture transport on precipitation stable isotopes (δO and d-excess) in the central Himalayas is still unclear, although crucial to understand the climatic archives recorded in, e.g., ice cores. Here we present measurements of stable isotopes in precipitation at two stations (Yadong and Pali) in the central Himalayas during 2014-2015. Combined with simulations from the dispersion model FLEXPART, we investigate possible effects on precipitation stable isotopes related to changes in moisture sources and convections in the region. Here we show that precipitation stable isotopes and convective activities are different between 2014 and the El Niño year 2015 in Yadong Valley. Our results show that enriched O and high d-excess in precipitation during the 2015 monsoon season compared to 2014 is accompanied by a change in δO lapse rate as an outcome of changes in upstream convection which alters δO through kinetic fractionation. During 2015, isotopic variations are linked to larger contributions of moisture from the Arabian Sea and the Indian continent, as well as lesser from the Bay of Bengal (BoB). Outgoing longwave radiation and moisture flux divergence analysis further confirms that contribution from continental evaporation dominates the moisture supply in the central Himalayas with a lesser contribution from convection over the BoB during the 2015 monsoon season, compared with 2014. These findings provide insights into climatic interpretations of paleo-isotopic archives regarding responses to changes in moisture transport to the central Himalayas.

Different Dynamics Drive Indian Ocean Moisture to the Southern Slope of Central Himalayas: An Isotopic Approach

“…Indeed, previous studies have used oxygen isotope measurements in precipitation (δ 18 O p ) in the Himalayas and adjacent regions to reveal moisture sources and moisture transport processes (Acharya et al., 2020; Adhikari et al., 2020; Axelsson et al., 2023; Chakraborty et al., 2016, 2022; Gao et al., 2011; Islam et al., 2021; Jeelani & Deshpande, 2017; Jeelani et al., 2018; Rahul & Ghosh, 2019; Ren et al., 2017; Sinha et al., 2019; Yu et al., 2016). For example, some studies have found that the δ 18 O p values on the southern slope of the Himalayas change significantly in response to different moisture transported by the westerlies and the Indian summer monsoon (Acharya et al., 2020).…”