70万年以来西太平洋暖池区硅质生产力记录及其气候效应

Silicic productivity record in the Westen Pacific Warm Pool in the last 700 ka and its climatic effect

西太平洋暖池(WPWP)的硅质生产力水平在调节第四纪全球大气CO_(2)分压的变化上发挥着重要作用,但其控制因素尚存争议。本研究对位于WPWP核心区的MD06-3047岩芯进行了生源蛋白石分析,探讨了700 ka以来WPWP的硅质生产力的控制因素及气候效应。研究发现,700 ka以来WPWP硅质生产力变化呈现显著的冰期-间冰期旋回,基本在冰期较高,间冰期较低。其主要控制因素可能是东吕宋陆架沉积物风化输入、亚洲风尘输入和温跃层深度(DOT)变化。南大洋中层水的“硅溢漏”可能无法对此海区产生显著影响。冰期时的低海平面,导致热带火山弧附近裸露的陆架沉积物的物理剥蚀和硅酸盐风化,淡水输入为WPWP提供了更多的硅酸;冰期时增强的风尘供应为WPWP提供了更多的Fe;冰期时较浅的DOT使表层海水的营养物质垂向空间变小,滞留时间增多。这些因素使冰期的WPWP生产力增高,有可能降低了大气CO_(2)分压。

The Quaternary silicic productivity levels in the Western Pacific Warm Pool(WPWP)are believed to play a crucial role in regulating changes in global atmospheric CO_(2) partial pressure.However,there is a debate regarding the factors that control the productivity levels.We examined the biogenic opal of core MD06-3047,which is located in the central region of the WPWP,to investigate the controlling factors and climatic effects on silicic productivity over the past 700 kyr.Our findings indicate that the variation in silicic productivity in the WPWP exhibits significant glacial-interglacial cycles:higher levels during glacial periods while lower levels during interglacial periods.The primary controlling factors might be sediment erosion and weathering on the East Luzon continental shelf,the aeolian dust input,as well as the depth of the thermocline(DOT).The silicic acid leakage from the Southern Ocean may not have a significant impact.During glacial periods,physical erosion and silicate weathering of exposed continental shelf sediments near tropical volcanic arcs were intensified,and so did the dust input,which resulted in increased input of silicate and iron to the WPWP.The shallower DOT during glacial periods led to a smaller nutrient vertical space and increased retention time,thereby increasing the glacial productivity of the WPWP,and potentially reducing the partial pressure of atmospheric CO_(2).