中亚黄土粉尘与冰冻圈演化、太平洋生产力和全球变化的联系

The dynamic links between Central Asian dust emission,Tibetan cryosphere,Pacific productivity and global climate changes

粉尘循环是地球系统表层岩石圈、水圈、冰冻圈、大气圈和生物圈之间相互作用的重要纽带.中纬度陆地岩石圈经地表风化、冰川磨蚀形成大量富营养物质的粉砂,经流水搬运至内陆盆地,在干旱气候和风力作用下,形成大量沙尘输送至海洋,显著影响海洋生物地球化学过程和全球气候.以中亚内陆为代表的亚洲沙漠及荒漠戈壁区是地球上最重要的沙尘源区之一,是上述过程的最典型代表,且影响最大.然而,目前对于地质时期“中亚内陆粉尘活动和营养物质组成是如何变化的?其与构造侵蚀、冰冻圈演化和大气环流的关系如何?对大洋生产力和全球碳循环的影响是什么?等一系列问题仍缺乏研究,制约了对亚洲粉尘释放在全球生物地球化学循环和气候变化中重要角色的理解。鉴于此,本文通过系统梳理和总结中亚黄土粉尘地层年代、物质来源和营养物质组成、传输过程以及粉尘的大洋铁施肥效应,对地质时期中亚粉尘活动和营养物质演化历史以及驱动机制进行了系统阐述;评估了粉尘营养物质输入对太平洋生产力和全球碳循环与气候变化的影响;提出未来需要通过进一步加强岩石圈-冰冻圈-粉尘产量和营养物质含量关系研究,开展大空间范围和长时间尺度上亚洲粉尘营养元素含量及化学形态组成及其与大洋生物活动与多样性演化等分析,然后基于由源到汇的陆海记录对比和数值模拟,是详细揭示亚洲粉尘输入增加-海洋固碳增强-大气CO_(2)减少”的碳循环链式动力过程的关键.

The dust cycle plays a critical role in the interactions between the lithosphere,hydrosphere,cryosphere,atmosphere and biosphere at the surface of the Earth systems.Intensive surface weathering and glacial abrasion of bedrocks of the lithosphere have produced a large amount of nutrient-rich silt.These clastic materials were transported by rivers to inland basins and subsequently available for atmospheric dust under the influence of arid climates and wind,profoundly impacting marine biogeochemical processes and global climate through the dust transport processes from land to ocean.At the global scale,dust emitted from Asian arid and semi-arid regions is transported over long distances in the upper atmosphere,and it is an important source of atmospheric mineral dust in the Northern Hemisphere.To date,however,there is a lack of clear and distinct understanding about the temporal variations in dust activities and dust nutrients of Central Asia as well as their relationships with tectonic activities,global cooling and atmospheric circulation system since the late Cenozoic.Moreover,little information is known about the potential link between the nutrient supply of Central Asian dust and changes in primary productivity of the North Pacific in the geological past.Consequently,large uncertainties exist about the critical role of Asian dust emission in modulating marine biogeochemical cycles and global climate.