西太平洋风尘沉积记录研究进展

RESEARCH PROGRESS ON EOLIAN DUST RECORDS IN THE WEST PACIFIC

研究海底风尘组份、来源和通量的地质记录,对于理解风尘在行星辐射平衡、全球大洋的营养盐供应及碳循环中的作用,以及源区古气候和古大气环流重建有着非常重要的意义。作为全球第二大风尘源区的亚洲内陆,其风尘产物主要被东亚冬季风及西风带携带至西太平洋。现有西太平洋风尘沉积记录的工作主要集中在冰期-间冰期时间尺度,尤其近几年在西菲律宾海和赤道太平洋第四纪风尘物源及通量变化方面取得了重要的进展,在日本海中新世以来的长期风尘记录及其驱动机制方面也获得了重要认识。至少在晚第四纪以来的冰期-间冰期时间尺度上,从高纬度到赤道甚至南极的全球范围,风尘通量在冰期约高出间冰期2—3倍,表明冰期风尘源区更加干旱而风力更为强劲。在新生代以来,西太平洋的长期风尘输入主要反映了亚洲内陆干旱逐渐增强,是受到青藏高原隆起和全球变冷的共同影响。但是,总体上西太平洋风尘沉积的研究程度非常低,突出反映在以下几个方面:风尘从源到汇搬运和沉积过程的现代观测的缺乏、大洋风尘组分含量及通量定量化中的误区、西太平洋风尘沉积长期演变特征、机制及风尘长期输入对大洋生产力及全球碳循环的影响方面的研究亟待加强。

Research on geologic records of dust composition, sources and flux is important for understanding the role of dust in planetary radiation balance, nutrient addition to the oceans, and carbon cycle, and for paleoclimatic reconstructions. As the second largest dust region among the world, Asia delivered the most of the dust moving eastward to the West Pacific by the East Asian winter monsoon and Westerly jet. Previous studies about eolian records in the West Pacific focus mainly on the glacial-interglacial timescale. Especially, research about the provenance and flux of eolian dust to the West Philippine Sea and equatorial Pacific since the late Quaternary, and the long-term Asian eolian deposition in the Japan Sea since the Miocene, and its forcing mechanism have achieved great progress. At least on the glacial-interglacial timescale since the late Quaternary, on the global-scale from the high-latitude to equatorial, and even to Antarctic, eolian fluxes were 2—3 times higher during a glacial time than an interglacial period. A dustier Earth during glacial periods is likely due to greater aridity in the source region, less vegetation, and stronger winds. Since the Cenozoic, the long-term eolian flux to the West Pacific reflects a stepwise drying in Asian inland, which in turn was controlled by the combined effect of Tibetan uplift and global cooling. However, the research degree of eolian deposition in the West Pacific actually was very low. In the future, it is suggested to strengthen the studies, especially in the areas of 1. continuous observation on eolian dust transport and deposition processes from source to sink; 2. unbiased quantitative estimates of the content and flux of true eolian dust in the marine record; and 3. the evolution, forcing mechanism, and nutritional effect of eolian dust to the West Pacific on long-term timescale since the Cenozoic.