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Greenhouse Gas and Ice Volume Drive Pleistocene Indian Summer Monsoon Precipitation Isotope Variability
Author(s) -
McGrath Sarah M.,
Clemens Steven C.,
Huang Yongsong,
Yamamoto Masanobu
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl092249
Subject(s) - speleothem , climatology , monsoon , northern hemisphere , precipitation , ice core , east asian monsoon , geology , southern hemisphere , atmospheric sciences , orbital forcing , troposphere , environmental science , meteorology , insolation , geography , cave , archaeology
Orbital‐scale Indian Summer Monsoon variability is often interpreted as a direct response to northern hemisphere summer insolation. Here we present a continuous (0–640 kyr) orbital scale precipitation isotope (δD precip ) record using leaf wax δD from the core monsoon zone of India. The δD precip record is quantitatively coherent with, and δD precip minima in phase with, greenhouses gas maxima, and ice volume minima across all orbital bands. The δD precip record is also coherent and in phase with the two existing orbital‐scale Indian speleothem δ 18 O records, demonstrating a consistent regional response among independent proxies. These findings preclude interpretation of Indian precipitation isotope records as a direct response to northern hemisphere summer insolation. Rather, they dominantly reflect changes in moisture source and transport paths associated with changes in greenhouse gases and ice volume. The orbital‐scale precipitation isotope responses of the Indian and East Asian monsoon systems are uncoupled and are driven by different forcings.