GEOGRAPHY

Solar radiation, ice levels and carbon dioxide affect the Quaternary climate of East Asia However, regional and seasonal differences are exhibited


Typical loess, lakes, stalagmites, and marine sediments in East Asia and surrounding waters.

Responses of summer temperature (a), precipitation (b) and annual average temperature (c) and annual precipitation (d) to changes in Earth orbital parameters, CO2 and ice levels.

Summer and annual precipitation variations in northern China (a and c, 30-40°N) and southern China (b and d, 30-40°N). Images are provided by the author of the paper.

A large number of existing research literature shows that different geological carriers from the East Asian continent and the surrounding oceans reveal significant 10,000-year-scale fluctuations in the Quaternary East Asian monsoon climate. However, the period and magnitude of the substitution index changes in these vectors vary greatly. For example, indicators such as the particle size and susceptibility of loess show that the East Asian monsoon has a significant 100,000-year glacial period rotation, while the stalagmite oxygen isotope record reflects a change in monsoon intensity dominated by a 20,000-year precession cycle.

This difference thus leads to confusion about the dynamics of monsoon variation, i.e., how solar radiation and high-latitude ice levels affect orbital-scale East Asian monsoon variability.

Recently, the research team of Sun Youbin of the Institute of Earth Environment was invited by the editors of the Quaternary Science Review (QSR) to unite a number of scientists from Belgium and the United States to review the research progress of the variability characteristics and dynamics of the Quaternary East Asian monsoon orbital scale by combing the loess, lakes, stalagmites and ocean records in the East Asian monsoon region, combined with numerical simulation results, and believed that climate change in East Asia (such as temperature and precipitation) has obvious regional and seasonal characteristics. It is suggested that in the future, the direct comparison between quantitatively reconstructed climate variables and numerical simulation results needs to be strengthened to deepen the understanding of climate change dynamics at the Quaternary orbital scale. The content and results of his research were recently published online in Quaternary Science Reviews in an Invited Article.

The authors collected more than 50 geological records of the East Asian continent and the surrounding seas, discussed the similarities and differences between the East Asian monsoon and the Indian summer wind changes revealed by loess, lake and ocean sedimentary indicators, and concluded that there are roughly four manifestations of the evolution of the Quaternary orbital scale climate cycle: (1) 40,000 years to 100,000 years; (2) 2/40,000 years into a mixed 2/4/100,000 years; (3) 20,000 years to a mixed 2/4/100,000 years; (4) Continuous 2/4/100,000 years and no cyclical transformation.

Based on HadCM3 simulation results, they found seasonal and regional differences in the response of precipitation and temperature to forcings such as orbital parameters, CO2, and ice volume. Summer temperature and precipitation changes in the northern region (30-60 °N) are mainly affected by precession, while the temperature and precipitation in the southern region (0-30 °N) are also affected by CO2 and ice volume changes in addition to precession, respectively; The annual average temperature and annual precipitation changes also showed north-south differences for the three forcing factors.

In addition, based on HadCM3 simulations, the authors estimated the changes in summer precipitation and annual precipitation over the last 2.6 million years, and their evolutionary cycles showed significant regional differences.

Comparing the changes in the loess, lakes and stalagmite indicators in northern China with the simulation results, it is shown that the periodic differences shown by different indicators may be caused by the differences in the response of the indicators to temperature and precipitation. Lake pollen and loess carbonate isotopes mainly respond to average annual mild annual precipitation changes, with a 100,000-year cycle rotation in the middle and late Pleistocene, while stalagmite oxygen isotopes may mainly reflect summer precipitation changes, so they are dominated by a 20,000-year cycle.

Combining geological records and numerical simulations, the authors argue that solar radiation, ice volume, and CO2 changes will all affect Quaternary climate change in East Asia, but their effects on different climate elements show regional and seasonal differences. Therefore, different carriers and indicators have different sensitivities to factors such as temperature and precipitation, and the response of temperature and precipitation to different forcing factors is superimposed, resulting in a variety of periodic evolution characteristics of climate change at the Quaternary orbital scale. (Source: China Science Daily, Zhang Xingyong, Yan Tao)

Related paper information:https://doi.org/10.1016/j.quascirev.2022.107593



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