Itrace chang analysis11/21/2023 ![]() We also analyzed a transient climate model simulation (comprising orbital (ORB) + greenhouse (GHG) + ice sheet (ICE) forcings) through the last 300 ka using the fully coupled National Center for Atmospheric Research-Community Climate System Model version 3 (NCAR-CCSM3) model 26, 27, and studied the periodicity of simulated rainfall variations and the drivers of this periodicity in East-Southeast Asia. 1a) to quantitatively reconstruct the rainfall changes in northern China over the last 400 ka. To address these conundrums, we present a silicate weathering record from Site U1429 (31☃7.04’N, 128★9.85’E) of the International Ocean Discovery Program (IODP) in the northern East China Sea (Fig. Such controversial complicates our understanding of hydroclimate in East Asian monsoon domain and surrounding tropical climate zone associated with high-low-latitude climate interactions. This can be supported by recently rainfall reconstructions in the Tengger Desert in northern China, which revealed prominent precession cycles in local rainfall variation, challenging the view that high-latitude ice sheets are the primary driver of northern China monsoon hydroclimate 25. Even when ice-sheet and greenhouse gas forcings were included in these simulations, the dominant precession signal can still be observed in northern China 14, 24. Another paradox is that most previous simulation studies have suggested the existence of strong precession forcing on the East Asian monsoon hydroclimate 18, 19, 20, 21, 22, 23. However, all recent precipitation isotope record reanalysis and model simulations have revealed that glacial-interglacial cycles are dominant in southern China 14, 15, even in tropical Southeast Asia 15, 16, 17, highlighting the dominant ice sheet and CO 2 forcing on the lower latitude hydroclimate. This results in dominant 100 ka cycle of summer monsoon climate in northern China but 23 ka cycle in southern China. ![]() ![]() ![]() Monsoon rainfall variabilities in the Loess Plateau and Yangtze River Valley in northern-central China are more sensitive to ice-sheet and CO 2 forcings and less sensitive to insolation forcing than that in southern China 9, 11, 12, 13. Such latitude dependent forcing of monsoon hydroclimates has also been proposed in the East Asian monsoon region. In contrast, high-latitude hydroclimate conditions tend to respond to ice-sheet and CO 2 forcings as a result of multiple atmospheric processes, thus suggesting strong glacial-interglacial cycles of 100 ka in these regions 8, 9, 10. This hypothesis has been tested in some early rainfall reconstruction and modeling studies in mid-low-latitude regions 3, 4, 5, 6, 7. Theoretically, precession forcing contributes more to the solar radiation amplitude received by Earth than obliquity or eccentricity 2, thus, the 23 ka cycle should be considered as the dominant mode affecting monsoon climate variations. Monsoons are seasonal variations in atmospheric circulations accompanied by the reversal of dry and wet surface climate conditions, and are mainly forced by seasonal pressure system shifts driven by the annual/seasonal solar radiative forcing cycle 1. This study highlights the seasonal contributions to orbital-scale rainfall changes, and sheds light on the Asian hydroclimate conditions associated with high-low-latitude climate interactions. Rainfall in the south is largely forced by high-latitude ice sheets, with enhanced spring and autumn rainfall in southern China and weakened rainfall in western Maritime Continent during glacial periods. We propose that rainfall mainly occurs in summer in the north, primarily driven by insolation. Here, by combining rainfall proxy records with multi-model simulations, dominant 23 ka rainfall cycle in northern China and 100 ka rainfall cycle in southern China and Southeast Asia were found. However, debates exist regarding these rainfall variations and forcings due to inconsistent reconstructions and simulations. Quaternary Asian low-latitude hydroclimate cyclicity has long been attributed to insolation forcing, in contrast to the dominant ice-sheet and CO 2 controls identified in mid-high-latitude regions.
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