Nature: New study finds ‘rain god’ in East Asian monsoon region For the first time, it has been revealed that tropical ocean warming may cause rainfall in the East Asian monsoon region

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Tropical ocean warming closely linked to increased rainfall in the East Asian monsoon region Photo courtesy of respondents

On October 20, Nature published online the latest scientific research results of Professor Zhai Zhixiang’s team at the State Key Laboratory of Marine Geology of Tongji University, which found that tropical ocean warming has an intensifying effect on the East Asian monsoon climate, explained for the first time the driving role of low-latitude marine processes in climate evolution from the perspective of energy, and provided the latest insights for solving the sea-land thermal cycle linkage.

The oceans are the largest heat reservoirs in the Earth’s climate system. Since the Industrial Revolution, the greenhouse effect of man-made release of carbon dioxide has caused global warming, in which more than 90% of excess heat enters the ocean. The tropical Indo-Western Pacific warm pool is the region with the highest surface sea temperature and the highest concentration of heat content in the world, constantly providing energy and water vapor for atmospheric upward movement and convective rainfall, and is also the “heat and steam engine” of the entire earth’s climate system.

Upper ocean heat is also a key driver of tropical storms (typhoons), which has continued to increase in recent years in the context of global warming, and is thought to be closely related to the increased destructive power of landfall typhoons in East Asia. However, the links and mechanisms between ocean heat and land rainfall are still not well understood.

The lack of modern instrumental observation data greatly limits the ability of human beings to predict and prevent extreme weather/climate disasters, and it is urgent to use geological records and numerical simulations to study the past changes in ocean heat content and its regulatory effect on the energy/water cycle between sea and land.

In collaboration with researchers from the University of Bremen in Germany, Rutgers University in the United States, the University of California, Santa Barbara, and the University of Kiel in Germany, the team used for the first time to reconstruct the changes in the heat content of upper seawater (0 to 200 meters) in the past 360,000 years by using the planktonic foraminifera microfossils in 10 deep-sea sedimentary cores in the warm pool area, and found that the reconstruction record of the heat content of the warm pool was very consistent with the change pattern and amplitude of the heat content curve of the transient simulation of the numerical model of the earth’s climate system. The team also reconstructed the residual oxygen isotopes of the surface seawater in the warm pool area, and the results were consistent with the change in the heat content of the warm pool, both of which changed synchronously with the atmospheric rainfall oxygen isotopes recorded by Chinese stalagmite in the precession cycle: that is, the heat content of the warm pool increased, corresponding to the heavier residual oxygen isotope of seawater and the lighter oxygen isotope of stalagmite.

“This suggests that during astronomical cycles on a 10,000-year scale, heat changes in warm pools can regulate water vapor transport between the Pacific Ocean and the Asian continent.” “When the heat of the warm pool increases, the evaporation of the tropical sea surface increases, water vapor gathers, and it is transmitted to adjacent land in the form of monsoons and typhoons, resulting in increased rainfall in East Asia,” said Zhai. ”

“From an energetic point of view, the coupling between ocean heat content and monsoon changes is key to regulating the global hydroclimate, both of which are regulated by changes in solar radiation at astronomical scales.” Co-author Mahyar Mohtadi, a professor at the University of Bremen in Germany, describes the contribution of this study to a comprehensive understanding of the global hydrological cycle.

Yair Rosenthal, a professor at Rutgers University in the United States, said: “Our work proposes that changes in the thermal structure of the ocean are the most critical determinants of ocean water vapor and latent heat transport and their transport to land, compared with seawater surface temperature. ”

This study comprehensively uses modern observations, paleoenvironmental surrogate indicators, and transient simulations of sea-air coupling models and water isotope numerical models to explore the latent heat transport of water vapor from the perspective of the upper ocean heat content (rather than surface seawater temperature) in the warm pool area, and measure the intensity of the global monsoon water cycle through the water isotope gradient between sea and land, which not only expands the new field of energetic research of paleooceanic and paleoclimate, but also provides a new idea of “discussing the present with the past” for modern and future climate change. (Source: China Science News, Zhang Shuanghu, Huang Xin)

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