GEOGRAPHY

The temporal and spatial evolution of precipitation in the Indo-Pacific convergence area over the past 40,000 years


Recently, the International Nature Index journal Geophysical Research Letters (GRL) published online the latest research results “Millennial-scale precipitation” in cooperation between Wan Shiming’s research team of the Institute of Oceanography of the Chinese Academy of Sciences and the University of Saclay in Paris, University College London and the French Climate and Environmental Science Laboratory variability in the Indo-Pacific region over the last 40 kyr”。

The Indo-Pacific Warm Pool is the highest sea temperature in the world, known as the global “heat engine”, and plays an important role in the climate system. Future climate prediction in the Indo-Pacific Convergence Area requires not only a full understanding of the impact of human activities on the climate, but also a clarification of the change law of natural climate factors, especially the detailed depiction of the potential feedback effect of natural climate factors after superimposed on human activities, but the actual observation record is generally short, which limits the understanding of the region’s climate evolution in the context of global warming. Therefore, it is urgent to reveal the history and law of changes in natural climate factors in the Paleoclimatology study of the Indo-Pacific Junction to make up for the lack of instrumental records, provide boundary conditions for model prediction, and provide reference for how humans can cope with current global warming.

Currently, alternative records of precipitation reconstruction in this region are mostly based on elemental ratios from hydrogen-oxygen isotopes or X-ray fluorescence scans, but both methods have some limitations. Therefore, the development of independent proxy indicators, reconstruction of independent precipitation evolution history, and cross-verification of multiple indicators can better reveal the response of tropical precipitation to regional ocean-atmosphere processes. Based on this idea, the researchers used deep-sea sedimentary cores in the core area of the warm pond to reconstruct continuous weathering records spanning the past 40,000 years, with a temporal resolution of 80 years for the first time. The continental weathering record is mainly affected by precipitation and temperature changes, and there has been no significant millennial timescale fluctuation in the temperature change in the Indo-Pacific junction for 40,000 years, so the researchers believe that the fluctuation of the millennium timescale in the reconstructed weathering record is mainly controlled by local precipitation intensity changes, and the change of precipitation intensity in this region is directly related to the intensity evolution of atmospheric depth convection in the Indo-Pacific warm pool. The results also show that the evolution of atmospheric depth convection in the Indo-Pacific warm pool over 40,000 years is very consistent with the ENSO-like system and the Pacific Walker circulation intensity changes.

On this basis, the researchers further summarized the precipitation records reconstructed by multiple indicators in the region, and analyzed and found that: on the millennium time scale, the western side of the Indo-Pacific Convergence Zone (Eastern Indian Ocean) is mainly affected by the Tropical Convergence Zone Migration (ITCZ), and the precipitation is distributed in the opposite direction, while the precipitation on the eastern side (Western Pacific) is distributed in a “sandwich” structure, mainly controlled by the ENSO-like system. The results of the paleorecord results are also well reproduced in the TraCE-21 model of the single-factor drive of meltwater in the North Atlantic, suggesting that the meltwater drive in the North Atlantic may be the cause of the differential precipitation distribution on the millennial time scale in the Indo-Pacific Junction. This study reveals the spatial and temporal distribution characteristics of precipitation in the Indo-Pacific Junction over the past 40,000 years, and for the first time discovers the differential distribution characteristics of precipitation on the east and west sides, distinguishing the different impacts of the ITCZ and ENSO systems in this region. The results provide a boundary framework and results validation for high-resolution atmospheric depth convection models of precipitation and warm pools in the Indo-Pacific Junction. According to the inference that “wet people are wetter” in the context of global warming, the distribution of local precipitation differences in the Indo-Pacific convergence area may intensify in the future.

Figure 1. Comparison of spatial distribution modes of modern (a) and last glacial (b and c) precipitation in the Indo-Pacific Junction. Blue areas indicate increased precipitation, and orange areas indicate decreased precipitation.

Figure 2. Millennial timescale weathering versus climate record. Figures a, c and d are the weathering records reconstructed in this study, Figure B is the ENSO-like system change, Figure E is the sea surface temperature change, and Figure F is the sea level change curve. The figure on the right shows the spectral analysis results of the corresponding curve.

The first and corresponding author of the paper is Yu Zhaojie, associate researcher of the Institute of Oceanology, Chinese Academy of Sciences. This research was supported by the National Natural Science Foundation of China, the Strategic Leading Science and Technology Project of the Chinese Academy of Sciences, and the Natural Science Outstanding Youth Fund of Shandong Province. (Source: Institute of Oceanology, Chinese Academy of Sciences)

Related paper information:https://doi.org/10.1029/2022GL101646

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