青藏高原区域抬升对轨道尺度亚洲季风调制效应的模拟研究

REGIONAL UPLIFT OF THE TIBETAN PLATEAU MODULATES THE SENSITIVITY OF ASIAN SUMMER PRECIPITATION TO ORBITAL FORCING

本研究利用大气环流模式,基于青藏高原及周边区域的8个地形抬升情景,并考虑地球轨道参数(强弱岁差和高低地轴倾角)组合,开展了24组敏感性数值试验,集中研究了地形抬升对轨道尺度欧亚内陆干旱和季风降水的调制作用。结果分析表明,整体而言,青藏高原区域地形的阶段性逐步抬升调制的欧亚大陆降水对岁差和地轴倾角的响应具有类似的分布特征,但响应强度略有差异。此外,不同地形抬升情景下,降水对轨道强迫的响应呈现出区域差异。其中,亚洲内陆干旱区是区域地形调制轨道强迫作用的高敏感区域,尤其伊朗高原抬升有效强化了轨道导致的降水增加信号;青藏高原中部、东部和北部的抬升则通过引导季风环流向北辐合加强,增强了岁差和地轴倾角引起的北东亚季风降水幅度;伊朗高原抬升有效地加强了中国黄土高原降水对地轴倾角的响应。这些试验结果揭示青藏高原是东亚夏季季风的轨道尺度变率的潜在影响因子,这可为地质记录揭示的季风在轨道时间尺度上变率强化现象提供机制上的解释。

Since the Cenozoic,high⁃resolution orbital⁃scale geological records have revealed long⁃term fluctuations in the dominant period and amplitude of Earth's climate change controlled by orbital parameters,which are closely related to the long⁃term evolution of climate boundary conditions,including asymmetric land⁃sea distribution,large fluctuations in atmospheric CO_(2),opening and closing of sea lanes,and tectonic uplift of mountain ranges.The East Asian monsoon system is an important component of the Earth's climate system and plays a key role in East Asian climate patterns.Orbital⁃scale changes in the East Asian monsoon system are a key issue in palaeoclimate research,as they significantly influence the geography of East Asia.Investigating the modulation of orbital⁃scale climate change by tectonic uplift on the Tibetan Plateau will contribute to a deeper understanding of how the Asian monsoon arid environment responds to orbital forcing.In this paper,we focus on the modulation of orbital⁃scale Eurasian inland drought and monsoon precipitation by tectonic uplift by conducting 24 sets of sensitivity numerical experiments using an atmospheric general circulation model based on eight tectonic uplift scenarios for the Tibetan Plateau and surrounding regions,considering combinations of Earth orbital parameters(strong and weak precession and high and low obliquity).The results of the modelling study have led to the following conclusions,overall,the response of precipitation to precession and obliquity in Eurasia modulated by the staged gradual uplift of the regional topography of the Tibetan Plateau has similar distributional characteristics,but with slight differences in response intensity.In addition,there are regional differences in the response of precipitation to the orbital forcing under different scenarios of topographic uplift.In particular,the uplift of the Iranian Plateau effectively enhances the signal of orbital⁃induced precipitation increase;the uplift of the central,eastern and northern Tibetan Plateau enhances the magnitude of precession⁃and obliquity⁃induced Northeast Asian monsoon precipitation by directing the northward convergence of the monsoon circulation;the uplift of the Iranian Plateau effectively enhances the response of precipitation to obliquity on the Loess Plateau of China.These experimental results demonstrate that the Tibetan Plateau is a potential influence on the orbital variability of the East Asian summer monsoon,which could provide a mechanistic explanation for the enhancement of monsoon variability on orbital time scales revealed by the geological record.