The Effect of Monsoon Circulation on the Stable Isotopic Composition of Rainfall

Abstract

Understanding the factors that control the variability of oxygen isotopic ratios (δ18O) of Indian Summer Monsoon (ISM) rainfall (δ18Op) is of vital importance for the interpretation of δ18Op derived from climate proxies (e.g., speleothem and tree ring cellulose) of this region. Here we demonstrate the importance of moisture transport pathways on spatiotemporal variations of ISM δ18Op using a new set of daily observations from central and northern India and previously reported data aided by simulations from an isotope‐enabled General Circulation Model. 18O‐depleted rain events are characterized by a higher number of air parcel back trajectories through the Bay of Bengal branch of moisture transport, while those through the Arabian Sea branch are associated with 18O enriched rain events. This effect is observed on intraseasonal to interannual timescales in the long‐term observations at New Delhi as well. Thus, the shift in moisture transport regimes must be considered when interpreting δ 18Op from climate proxies of the ISM region.

The Indian Summer Monsoon from a Speleothem δ18O Perspective—A Review

“…They suggested that the improvements were due to the role of large-scale atmospheric dynamics on ISM rainfall and, hence, on δ 18 O rainfall . An increasing number of recent studies produce similar results suggesting that it is large-scale circulation rather than local rainfall amount that controls δ 18 O rainfall in the ISM region (e.g., References [96,97]). δ 18 O rainfall is further modified in its journey from the surface to the drip site in the cave and during precipitation of the stalagmite [88].…”

Innovative materials of this era for toughening the epoxy matrix: A review

“…The absolute number of particles would rise rapidly by a factor of 1,000 upon changing the particle size by a factor of only 10, for example, from 1 to 100 nm in turn generates a new material behavior, which is widely determined by interfacial interactions, offering unique properties and a completely new class of materials [44,45]. It is experimentally verified by research groups all over the world, that nanoparticles of metallic or inorganic type verify the ability to reinforce effectively both thermoplastic as well as thermosetting polymer matrices [46,47]. In particular, the reinforcement covers improvements of the flexural modulus without losing flexural strength.…”

Did the Harappan settlement of Dholavira (India) collapse during the onset of Meghalayan stage drought?

“…This is quite unlikely given the subcontinent‐scale observation of diminishing rainfall from 7000 years BP (mid‐Holocene) onward provided by various climate proxies (Sarkar et al ., , and references therein). More importantly, however, recent high‐resolution δ 18 O measurements of monsoonal precipitation at multiple stations across India clearly suggest that, contrary to normal belief, there is a negligible contribution of the amount effect in Indian monsoonal rain (Eastoe and Dettman, ; Midhun et al ., ). If so, the only plausible source(s) of depleted water can be the extra‐peninsular rivers and their tributaries of the Himalayan region where glacial meltwater can contribute to generate a river water δ 18 O of −12‰ (Lone et al ., ; Laskar et al ., ).…”

“…The Indus or its distributaries do not have such values in winter. The monsoonal rains have annual weighted δ 18 O values of between −6 and −5‰ (Sengupta and Sarkar, 2006;Deshpande et al, 2010;Midhun et al, 2018). River water δ 18 O data for the Kachchh or adjoining Rajasthan are not available.…”