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Methane, Monsoons, and Modulation of Millennial‐Scale Climate
Author(s) -
Thirumalai Kaustubh,
Clemens Steven C.,
Partin Judson W.
Publication year - 2020
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 - 10.1029/2020gl087613
Subject(s) - speleothem , monsoon , climatology , orbital forcing , middle latitudes , teleconnection , geology , ice core , climate change , atmospheric sciences , precession , latitude , oceanography , physics , insolation , geography , el niño southern oscillation , astronomy , cave , archaeology , geodesy
Earth's orbital geometry exerts a profound influence on climate by regulating changes in incoming solar radiation. Superimposed on orbitally paced climate change, Pleistocene records reveal substantial millennial‐scale variability characterized by abrupt changes and rapid swings. However, the extent to which orbital forcing modulates the amplitude and timing of these millennial variations is unclear. Here we isolate the magnitude of millennial‐scale variability (MMV) in two well‐dated records, both linked to precession cycles (19,000‐ and 23,000‐year periodicity): composite Chinese speleothem δ 18 O, commonly interpreted as a proxy for Asian monsoon intensity, and atmospheric methane. At the millennial timescale (1,000–10,000 years), we find a fundamental decoupling wherein precession directly modulates the MMV of methane but not that of speleothem δ 18 O, which is shown to be strikingly similar to the MMV of Antarctic ice core δ 2 H. One explanation is that the MMV of methane responds to changes in midlatitude to high‐latitude insolation, whereas speleothem δ 18 O is modulated by internal climate feedbacks.