View in EDS

Seasonal Response of the Miocene Indonesian Throughflow to Orbital Forcing Buffered by an Open Seaway.

Saved in:
Bibliographic Details
Title: Seasonal Response of the Miocene Indonesian Throughflow to Orbital Forcing Buffered by an Open Seaway.
Authors: Li, Zhen1 (AUTHOR), Zhang, Yurui1 (AUTHOR) yuruizhang@xmu.edu.cn, Wei, Jilin2,3 (AUTHOR), Zheng, Weipeng2,3,4 (AUTHOR), Wang, Yuan1 (AUTHOR), Dai, Nan1 (AUTHOR), Tian, Jun5 (AUTHOR) tianjun@tongji.edu.cn
Source: Journal of Geophysical Research. Oceans. Apr2026, Vol. 131 Issue 4, p1-14. 14p.
Subject Terms: *Ocean currents, *Ocean circulation, *Paleoceanography, *Seasonal temperature variations, Miocene Epoch, Atmospheric models
Geographic Terms: New Guinea (Island), Indian Ocean, Pacific Ocean, South Pacific Ocean
Abstract: The Indonesian Throughflow (ITF) is a vital link between the Pacific and Indian Oceans, shaping Indo‐Pacific climate dynamics. While its variability during the Quaternary is well documented, its response to orbital forcing under different tectonic configurations remains unclear. Using climate simulations with minimum and maximum boreal summer insolation, this study investigates how orbital forcing modulates the ITF seasonal cycle. The results show that orbital changes produce distinct two‐phase seasonal ITF responses despite similar annual mean transport (difference within 1.0 Sv) under pre‐industrial (PI) conditions. During the boreal summer insolation maximum, orbital‐induced insolation changes amplify the boreal summer ITF from 16.9 Sv in the PI control condition to 18.0 Sv, while reducing the winter ITF by 3.6 Sv. These responses arise from changes in Pacific‐Indian sea surface height gradients, modulated by wind anomalies and freshwater‐salinity effects on inter‐basin pressure gradients linked to ITCZ migration. In the Miocene context, this two‐phase seasonal ITF response to orbital forcing is notably dampened. A more open Indonesian gateway—particularly the deepened New Guinea–Maluku passage—permits greater South Pacific inflow (∼91% vs. ∼20% in PI) and nearly doubles bidirectional exchange (23.9 Sv vs. 12.4 Sv in PI), with strong seasonal reversal flows. This enhanced connectivity buffers the ITF orbital‐scaled variability by allowing more symmetric and continuous inter‐basin exchange. These findings underscore how orbital forcing and seaway geometry jointly regulate tropical ocean circulation, offering insights for interpreting paleoceanographic records and understanding the Miocene climate system's response to orbital forcing. Plain Language Summary: The Indonesian Throughflow (ITF) is a major ocean current that moves warm water from the Pacific to the Indian Ocean, influencing climate patterns worldwide. We used advanced climate models to study how changes in Earth's orbit and the configuration of ocean gateways during the Miocene (about 15 million years ago) affected this current. The results show that both Earth's orbit—which determines how much solar radiation is distributed across the planet—and the shape of the seaways play important roles in controlling ITF strength. Today, the ITF varies markedly between summer and winter as orbital‐driven sunlight changes affect winds, sea surface height, and rainfall. However, the Miocene Indonesian seaway was wider and deeper, allowing greater South Pacific inflow and stronger two‐way exchange. This bigger, more open seaway made the ITF less sensitive to short‐term changes caused by Earth's orbit, suggesting that wider seaways help stabilize tropical ocean currents. Key Points: The Indonesian Throughflow shows a two‐phase seasonal response to orbital forcings, with opposite anomalies in summer and winterOrbital‐induced changes were suppressed in the Miocene by stronger bidirectional exchanges through a more open Indonesian seawayOpen gateways help stabilize tropical ocean circulation [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Oceans is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: GreenFILE
Description
Abstract:The Indonesian Throughflow (ITF) is a vital link between the Pacific and Indian Oceans, shaping Indo‐Pacific climate dynamics. While its variability during the Quaternary is well documented, its response to orbital forcing under different tectonic configurations remains unclear. Using climate simulations with minimum and maximum boreal summer insolation, this study investigates how orbital forcing modulates the ITF seasonal cycle. The results show that orbital changes produce distinct two‐phase seasonal ITF responses despite similar annual mean transport (difference within 1.0 Sv) under pre‐industrial (PI) conditions. During the boreal summer insolation maximum, orbital‐induced insolation changes amplify the boreal summer ITF from 16.9 Sv in the PI control condition to 18.0 Sv, while reducing the winter ITF by 3.6 Sv. These responses arise from changes in Pacific‐Indian sea surface height gradients, modulated by wind anomalies and freshwater‐salinity effects on inter‐basin pressure gradients linked to ITCZ migration. In the Miocene context, this two‐phase seasonal ITF response to orbital forcing is notably dampened. A more open Indonesian gateway—particularly the deepened New Guinea–Maluku passage—permits greater South Pacific inflow (∼91% vs. ∼20% in PI) and nearly doubles bidirectional exchange (23.9 Sv vs. 12.4 Sv in PI), with strong seasonal reversal flows. This enhanced connectivity buffers the ITF orbital‐scaled variability by allowing more symmetric and continuous inter‐basin exchange. These findings underscore how orbital forcing and seaway geometry jointly regulate tropical ocean circulation, offering insights for interpreting paleoceanographic records and understanding the Miocene climate system's response to orbital forcing. Plain Language Summary: The Indonesian Throughflow (ITF) is a major ocean current that moves warm water from the Pacific to the Indian Ocean, influencing climate patterns worldwide. We used advanced climate models to study how changes in Earth's orbit and the configuration of ocean gateways during the Miocene (about 15 million years ago) affected this current. The results show that both Earth's orbit—which determines how much solar radiation is distributed across the planet—and the shape of the seaways play important roles in controlling ITF strength. Today, the ITF varies markedly between summer and winter as orbital‐driven sunlight changes affect winds, sea surface height, and rainfall. However, the Miocene Indonesian seaway was wider and deeper, allowing greater South Pacific inflow and stronger two‐way exchange. This bigger, more open seaway made the ITF less sensitive to short‐term changes caused by Earth's orbit, suggesting that wider seaways help stabilize tropical ocean currents. Key Points: The Indonesian Throughflow shows a two‐phase seasonal response to orbital forcings, with opposite anomalies in summer and winterOrbital‐induced changes were suppressed in the Miocene by stronger bidirectional exchanges through a more open Indonesian seawayOpen gateways help stabilize tropical ocean circulation [ABSTRACT FROM AUTHOR]
ISSN:21699275
DOI:10.1029/2025JC023315