全新世亚洲季风百年-千年尺度变化的模拟研究进展

气候重建工作的深入开展极大地促进了全新世亚洲季风变化的研究,然而当前重建结果对亚洲季风的演变特征和机理存在很大争议,开展古气候模拟对理解全新世亚洲季风演变的时空特征和成因机制具有重要意义。为此,本文主要从气候模式模拟的角度回顾全新世亚洲季风百年-千年尺度变化的模拟研究工作,并将从外强迫和气候系统内部变率这两个角度对机制进行探讨。主要有以下进展:全新世瞬变模拟试验结果反映早全新世以来亚洲季风降水呈下降趋势,这主要受到地球轨道参数的影响,并通过改变海陆热力差异和半球间温度梯度来影响亚洲季风降水。在百年尺度弱季风事件上,模拟的8.2 ka BP时期的亚洲季风弱事件主要是由冰川融水触发,引起大西洋经向翻转环流AMOC减弱并通过大气遥相关导致季风降水减少;而4.2 ka BP时期模式模拟的亚洲弱季风事件主要是受内部变率所主导而并非外强迫因子影响。亚洲季风百年尺度变化的模拟研究主要集中在过去2 000年时段,中世纪气候异常期季风明显增强,而在小冰期逐渐减弱,太阳辐射和火山活动是影响其变化的主导因子,它们通过影响海陆热力差异、印—太海温变化来影响季风变化。

Centennial to millennial variability of the Asian monsoon during the Holocene: Progress in simulation studies

The development of climate reconstruction greatly promotes the study of Asian monsoon variability in the Holocene. However, the current reconstruction result on the characteristics and mechanisms of the Asian monsoon evolution remains controversial. Meanwhile, paleoclimate simulation can contribute significantly to the understanding of the temporal-spatial characteristics and genetic mechanisms of the Asian monsoon evolution in the Holocene. This paper reviews simulation studies on the centennial to millennial-scale Asian monsoon variations during the Holocene from the perspective of climate modeling, and discusses the mechanisms from the perspectives of external forcing and internal variability. Among the main progresses, the Holocene transient simulation results show a downward trend in the Asian monsoon precipitation since the early Holocene, which is thought to be affected mainly by the earth orbital parameters, as well as changes in land-sea thermal contrast and inter-hemispheric temperature gradient. For centennial-scale weak monsoons, simulation of a 8.2 ka BP weak monsoon event reveals glacial melting water as the main trigger for the weakening of Atlantic meridional overturning circulation and atmospheric teleconnection; whilst simulation of a 4.2 ka BP weak monsoon event indicates such event may be controlled by internal variability rather than external forcing. Simulation studies on the centennial-scale changes mainly focus on the past 2 000 years. The results show an obvious increase of Asian monsoon precipitation during the Medieval Climate Anomaly but a gradual decrease during the Little Ice Age. Solar radiation and volcanic activity play a crucial role in centennial-scale Asian monsoon variations through influencing land-sea thermal contrast and Indo-Pacific sea surface temperature change.