Changes in the earth's orbit can trigger sudden changes in climate
2021-11-11
Taking history as a mirror, we can know the rise and fall. This "history" is not only the evolution history of human civilization, but also the long history of natural changes on the earth. "Using the complex climate model, we conducted simulation experiments on climate transients in the past 30000 or 40000 years, which proved for the first time that the change of earth orbit can directly trigger climate catastrophe, and systematically demonstrated the dual regulation and control of earth orbit change on climate catastrophe." on November 4, the Earth Science excellence and innovation center of the Chinese Academy of Sciences (hereinafter referred to as the Chinese Academy of Sciences) Zhang Xu, a researcher at the Qinghai Tibet Plateau Research Institute and a professor at Lanzhou University, told Science and technology daily. This study provides a new dynamic model for understanding the trigger mechanism of Pleistocene climate catastrophe events. Relevant research results are published online in the journal Nature Geoscience. It can directly trigger the sudden change of Atlantic meridional overturning circulation About 2.7 million years ago, with the gradual development of the continental ice sheet in the northern hemisphere, the climate system began to experience the alternation of cold and warm on a 10000 year scale, that is, the well-known glacial interglacial climate cycle. Under the background of glacial climate, the global climate frequently appears Millennium scale climate catastrophe events. In the 1980s, some scholars pointed out that the main reason for the sudden change of climate was related to the change of meridional overturning circulation in the Atlantic Ocean. "This view has been widely recognized in more than 30 years of continuous research, but there are many speculations about its trigger mechanism. Some scholars suggest that it may be related to the internal variability of ocean circulation, or caused by the melting of ice sheet or sea ice. Others point out that atmospheric carbon dioxide concentration and the westerly belt in the southern hemisphere also play a positive role. However, these speculations are mainly concentrated in the earth system "Internal factors of the system," Zhang Xu said. A large number of previous studies have proved that the earth orbit change can regulate and control the occurrence of climate sudden change events through the change of internal climate factors (such as ice change), that is, the orbit has indirect regulation and control over climate sudden change. So, can the earth orbit change directly trigger the Millennium climate catastrophe? To this end, researchers first carried out climate transient simulation experiments in the past 40000 to 32000 years. In the experiment, the researchers only take the earth orbit parameters as the variation, while all other environmental variables such as ice and greenhouse gases remain constant, so as to test whether the earth orbit change can directly trigger the sudden change of the Atlantic meridional overturning circulation. The experimental results show that the Atlantic meridional overturned circulation is similar to the Millennium scale oscillation in the climate records, and the corresponding changes of temperature and precipitation are also in good agreement with the climate records. "China's loess, stalagmites and lakes clearly record Millennium scale abrupt events. These abrupt events have had a significant impact on China's natural environment. We have confirmed for the first time in the complex climate model that earth orbit changes can directly drive climate abrupt changes." Chen fahu, academician of the Chinese Academy of Sciences and director of the Institute of the Qinghai Tibet Plateau of the Chinese Academy of Sciences, stressed. It can help mankind establish a scientific understanding of the "acquired" Subsequently, the researchers carried out a single forcing experiment of orbital parameters, that is, only changing the inclination, eccentricity and precession of the earth's axis, so as to further characterize the impact of changes in different orbital parameters on climate change. It is found that the change of precession can regulate the transport intensity of atmospheric water vapor from the Atlantic Ocean to the Pacific Ocean by affecting the summer solar radiation in the low latitudes of the northern hemisphere, and then regulate the sea surface salinity of the North Atlantic, resulting in the sudden change of the Atlantic meridional reverse current. At the same time, the dip angle of the earth axis can regulate the seawater temperature and sea ice area in the deep water generating area of the North Atlantic by affecting the change of annual average solar radiation in the high latitudes of the northern hemisphere, and then affect the intensity of vertical mixing of surface seawater and cause sudden change. "These numerical experiments confirm that the change of a single orbital parameter can also directly trigger the mutation of the North Atlantic Ocean circulation, that is, the direct regulation and control of the orbital change on the climate mutation," Zhang Xu explained. In order to systematically clarify the law of the modulation of Millennium climate events by earth orbit change, researchers have summarized the dynamic conceptual model to explain the Millennium climate events in different periods of Pleistocene through a large number of numerical experiments. "Our model is proved to be applicable not only to the late Pleistocene, but also to the middle and early Pleistocene," Zhang Xu said. Chen fahu said that through these studies, we can determine that the Millennium scale climate events in the ice age since the Pleistocene are likely to have been controlled by the dual regulation of polar ice sheet changes and changes in earth orbit parameters. However, how orbital scale climate change and Millennium scale climate change affect the climate evolution since the Pleistocene needs to be further studied through the earth system model containing ice sheet dynamic process. "Through the research on the mechanism behind the ancient climate phenomenon, scientists have tried to reveal the impact of the synergy of climate processes at different time and space scales on climate change, and strive to master the law of climate evolution. This is not only of great and far-reaching significance for human beings to predict and deal with future climate changes, but also help human beings establish a more scientific and rational understanding of 'the day after tomorrow'." Chen fahu said. (Xinhua News Agency)
Edit：Chen Jie Responsible editor：Li Ling
Source：Science Daily
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