Global Speleothem Analysis Reveals State‐Dependent Hydrological Response to Orbital Forcing. James, A., Emile‐Geay, J., Partin, J. W., & Khider, D. Paleoceanography and Paleoclimatology, 40(8):e2024PA005098, August, 2025. ![Global Speleothem Analysis Reveals State‐Dependent Hydrological Response to Orbital Forcing [link]](https://bibbase.org/img/filetypes/link.svg "link")
Paper doi abstract bibtex Abstract 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 ‐driven climate change. , Plain Language Summary The dynamics of tropical and subtropical rain patterns, which provide water to hundreds of millions of people today, are not fully understood. In order to predict how they may change in the future, scientists study how these systems have responded to past climate changes using oxygen isotopes preserved in cave deposits called speleothems. This study analyzed speleothem records from around the world spanning hundreds of thousands of years, revealing new insights about how rainfall patterns respond to changes in sunlight driven by Earth's orbit. The relationship varies significantly by region ‐ in monsoon areas, rainfall closely follows cycles occurring every 19–23 kyrs, while other regions mainly reflect longer (100 kyr) glacial cycles. Most surprisingly, we found that during cold glacial periods, the relationship between rainfall and Earth's orbit largely disappears in monsoon regions, suggesting that precipitation patterns behave very differently in colder climates. The study also highlights methodological challenges in comparing rainfall records to incoming sunlight, showing that seasonal effects cannot be distinguished from physical delays without additional information. These findings demonstrate that the connection between Earth's orbit and rainfall patterns is more complex than previously thought, advancing our understanding of how rain systems may respond to climate change. , Key Points Global analysis reveals high variability in the seasonal and latitudinal relationship between speleothem δ 18 O and insolation Without mechanistic constraints, seasonal influence on δ 18 O cannot be distinguished from physical lags in orbital‐scale analyses Precessional coherence collapses during glacial periods while maintaining eccentricity band power, suggesting a state‐dependent response
@article{james_global_2025,
title = {Global {Speleothem} {Analysis} {Reveals} {State}‐{Dependent} {Hydrological} {Response} to {Orbital} {Forcing}},
volume = {40},
issn = {2572-4517, 2572-4525},
url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024PA005098},
doi = {10.1029/2024PA005098},
abstract = {Abstract
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 ‐driven climate change.
,
Plain Language Summary
The dynamics of tropical and subtropical rain patterns, which provide water to hundreds of millions of people today, are not fully understood. In order to predict how they may change in the future, scientists study how these systems have responded to past climate changes using oxygen isotopes preserved in cave deposits called speleothems. This study analyzed speleothem records from around the world spanning hundreds of thousands of years, revealing new insights about how rainfall patterns respond to changes in sunlight driven by Earth's orbit. The relationship varies significantly by region ‐ in monsoon areas, rainfall closely follows cycles occurring every 19–23 kyrs, while other regions mainly reflect longer (100 kyr) glacial cycles. Most surprisingly, we found that during cold glacial periods, the relationship between rainfall and Earth's orbit largely disappears in monsoon regions, suggesting that precipitation patterns behave very differently in colder climates. The study also highlights methodological challenges in comparing rainfall records to incoming sunlight, showing that seasonal effects cannot be distinguished from physical delays without additional information. These findings demonstrate that the connection between Earth's orbit and rainfall patterns is more complex than previously thought, advancing our understanding of how rain systems may respond to climate change.
,
Key Points
Global analysis reveals high variability in the seasonal and latitudinal relationship between speleothem
δ
18
O and insolation
Without mechanistic constraints, seasonal influence on
δ
18
O cannot be distinguished from physical lags in orbital‐scale analyses
Precessional coherence collapses during glacial periods while maintaining eccentricity band power, suggesting a state‐dependent response},
language = {en},
number = {8},
urldate = {2025-08-19},
journal = {Paleoceanography and Paleoclimatology},
author = {James, Alexander and Emile‐Geay, Julien and Partin, Judson W. and Khider, Deborah},
month = aug,
year = {2025},
pages = {e2024PA005098},
}
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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 ‐driven climate change. , Plain Language Summary The dynamics of tropical and subtropical rain patterns, which provide water to hundreds of millions of people today, are not fully understood. In order to predict how they may change in the future, scientists study how these systems have responded to past climate changes using oxygen isotopes preserved in cave deposits called speleothems. This study analyzed speleothem records from around the world spanning hundreds of thousands of years, revealing new insights about how rainfall patterns respond to changes in sunlight driven by Earth's orbit. The relationship varies significantly by region ‐ in monsoon areas, rainfall closely follows cycles occurring every 19–23 kyrs, while other regions mainly reflect longer (100 kyr) glacial cycles. Most surprisingly, we found that during cold glacial periods, the relationship between rainfall and Earth's orbit largely disappears in monsoon regions, suggesting that precipitation patterns behave very differently in colder climates. The study also highlights methodological challenges in comparing rainfall records to incoming sunlight, showing that seasonal effects cannot be distinguished from physical delays without additional information. These findings demonstrate that the connection between Earth's orbit and rainfall patterns is more complex than previously thought, advancing our understanding of how rain systems may respond to climate change. , Key Points Global analysis reveals high variability in the seasonal and latitudinal relationship between speleothem δ 18 O and insolation Without mechanistic constraints, seasonal influence on δ 18 O cannot be distinguished from physical lags in orbital‐scale analyses Precessional coherence collapses during glacial periods while maintaining eccentricity band power, suggesting a state‐dependent response","language":"en","number":"8","urldate":"2025-08-19","journal":"Paleoceanography and Paleoclimatology","author":[{"propositions":[],"lastnames":["James"],"firstnames":["Alexander"],"suffixes":[]},{"propositions":[],"lastnames":["Emile‐Geay"],"firstnames":["Julien"],"suffixes":[]},{"propositions":[],"lastnames":["Partin"],"firstnames":["Judson","W."],"suffixes":[]},{"propositions":[],"lastnames":["Khider"],"firstnames":["Deborah"],"suffixes":[]}],"month":"August","year":"2025","pages":"e2024PA005098","bibtex":"@article{james_global_2025,\n\ttitle = {Global {Speleothem} {Analysis} {Reveals} {State}‐{Dependent} {Hydrological} {Response} to {Orbital} {Forcing}},\n\tvolume = {40},\n\tissn = {2572-4517, 2572-4525},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024PA005098},\n\tdoi = {10.1029/2024PA005098},\n\tabstract = {Abstract \n 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 ‐driven climate change. \n , \n Plain Language Summary \n The dynamics of tropical and subtropical rain patterns, which provide water to hundreds of millions of people today, are not fully understood. In order to predict how they may change in the future, scientists study how these systems have responded to past climate changes using oxygen isotopes preserved in cave deposits called speleothems. This study analyzed speleothem records from around the world spanning hundreds of thousands of years, revealing new insights about how rainfall patterns respond to changes in sunlight driven by Earth's orbit. The relationship varies significantly by region ‐ in monsoon areas, rainfall closely follows cycles occurring every 19–23 kyrs, while other regions mainly reflect longer (100 kyr) glacial cycles. Most surprisingly, we found that during cold glacial periods, the relationship between rainfall and Earth's orbit largely disappears in monsoon regions, suggesting that precipitation patterns behave very differently in colder climates. The study also highlights methodological challenges in comparing rainfall records to incoming sunlight, showing that seasonal effects cannot be distinguished from physical delays without additional information. 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