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Asian summer monsoon (ASM) variability significantly affects hydro-climate, and thus socio-economics, in the East Asian region, where nearly one-third of the global population resides. Over the last two decades, speleothem δ18O records from China have been utilized to reconstruct ASM variability and its underlying forcing mechanisms on orbital to seasonal timescales. Here, we use the Speleothem Isotopes Synthesis and Analysis database (SISAL_v1) to present an overview of hydro-climate variability related to the ASM during three periods: the late Pleistocene, the Holocene, and the last two millennia. We highlight the possible global teleconnections and forcing mechanisms of the ASM on different timescales. The longest composite stalagmite δ18O record over the past 640 kyr BP from the region demonstrates that ASM variability on orbital timescales is dominated by the 23 kyr precessional cycles, which are in phase with Northern Hemisphere summer insolation (NHSI). During the last glacial, millennial changes in the intensity of the ASM appear to be controlled by North Atlantic climate and oceanic feedbacks. During the Holocene, changes in ASM intensity were primarily controlled by NHSI. However, the spatio-temporal distribution of monsoon rain belts may vary with changes in ASM intensity on decadal to millennial timescales.
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This content will become publicly available on August 1, 2026
Global Speleothem Analysis Reveals State‐Dependent Hydrological Response to Orbital Forcing
Tropical and subtropical hydrological systems are important to water resource management. To improve understanding of these dynamical systems, it is useful to probe their relationship with relevant forcings. Historically, insolation is believed to be a major driver of these dynamics, testable using speleothem stable oxygen isotope records, whose growth regions and precise chronologies enable detailed investigations of tropical/subtropical hydrology. Here we present a systematic analysis of long speleothem records examining the global relationship between and insolation across different timescales and regions. Our analysis reveals that the relationship between speleothem and insolation varies significantly by region, with no latitude, season, or periodicity of insolation bearing global relevance. We demonstrate that, when comparing speleothem to insolation curves, seasonal influence often cannot be distinguished from physical lags without additional constraints from modeling or theory. Most notably, we identify a previously unrecognized asymmetry whereby coherence in the precessional (19–23 kyr) band frequently collapses during glacial periods while maintaining power in the 100 kyr band. This suggests a fundamental reorganization of the hydrological cycle and its response to orbital forcing during glacial periods. Our results indicate that comparing speleothem to single insolation curves oversimplifies the complex relationship between orbital forcing and hydroclimate variability, highlighting our framework's utility for comprehensively exploring these interactions. These findings advance understanding of how mid‐to‐low latitude hydrology responds to external forcing–knowledge that may prove valuable as we face unprecedented CO2‐driven climate change.
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- Award ID(s):
- 2002556
- PAR ID:
- 10650801
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Paleoceanography and Paleoclimatology
- Volume:
- 40
- Issue:
- 8
- ISSN:
- 2572-4517
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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