Study Reveals Weathering History of Western Pacific Island Arc Over the Past 140,000 Years

The tropical western Pacific island arc is dominated by basalt-ultrabasic basalts. Under the combined influence of the suitable climate (high temperature and strong precipitation) in the tropical warm pool area and the steep elevation drop of the island (few lowland plains, weathered sediments can't be retained in the basin), the weathering and denudation rate are fast, and the impact on the Marine environment may be greater than the traditional expectation. What are the main mechanisms controlling tropical island arc weathering? How does such a large amount of basalt weathering respond to climate change?

Recently, researchers from China, South Korea, France, UK, and U.S.A. reconstructed the weathering history of the Western Pacific island arc over the past 140,000 years, combined with the simulation results of transient climate models, revealing the temporal and spatial distribution characteristics of deep convection-precipitation evolution in the warm pool.

The study was published in npj Climate and Atmospheric Science on Apr. 18.

Researchers selected core MD01-2385, located in the core area of the Western Taiwarm Pool, and extracted three mineralogical and elemental geochemical weathering records from northwest of New Guinea Island, to reconstruct the island's weathering history over 140,000 years. It is found that the weathering records of the western Pacific islands show the characteristics of precession cycle control, which is obviously different from the changes of sea surface temperature (SST) controlled by eccentricity.

"This phenomenon implies that the weathering record is mainly controlled by deep convection-precipitation evolution in the warm pool, and can therefore, be used to indicate the history of deep convection-precipitation evolution in the warm pool," said Dr. YU Zhaojie from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS), first author of the study.

By comparing other records in the warm pool area, it is found that although the evolution records of atmospheric deep convection in many warm pools are dominated by precession period, different records respond to different solar radiation months and have heterogeneity. Transient climate simulation results also show the existence of this heterogeneity, which is consistent with the modern precipitation distribution.

The research team further compared the records with the spatial scale of the maximum and minimum of the inversion of the Western Pacific sea surface pressure gradient revealed by transient climate simulations. It is found that the warm pool atmospheric deep convection may affect the east-west movement of the West Pacific subtropical high by regulating the changes of the sea surface pressure gradient in the West Pacific, and then affect the changes in the strength of the East Asian summer monsoon.

Dr. YU added: "Our work reveals the weathering history of the Western Pacific Island Arc over the past 140,000 years through a combination of records and simulations, and reveals a possible link between deep warm pool convection and changes in the mid-latitude Asian summer monsoon."

Fig. 1 Schematic diagram of research station location and regional environment.

Fig. 2 Weathering records of tropical Western Pacific islands over 140,000 years.

Fig. 3 Changes in the Western Pacific Sea surface pressure gradient at precession maxima and minima simulated by transient climate models.

Yu, Z., Ruan, J., Song, L. et al. (2024). Late Pleistocene island weathering and precipitation in the Western Pacific Warm Pool. npj Clim Atmos Sci, 7, 91.

(Text by YU Zhaojie)

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