On the distribution of 231Pa and 230Th in the Indian Ocean

个人介绍

Yiming Luo is a Professor of marine biogeochemistry in the School of Marine Sciences, Sun Yat-sen University. He worked with Prof. Roger Francois to earn his PhD in University of British Columbia at 2013 and spent 3 years (2013-2016) in Dalhousie University to work as a postdoc with Prof. Bernard P. Boudreau. He is active in conducting research related to U-series isotopes in the ocean and the deep sea carbonate system. In the past few years, his publications have been focused on topics in chemical oceanography and marine geology, such as cycling of CaCO₃ and reconstruction of overturning circulation.

报告摘要

Sedimentary ²³¹Pa/²³⁰Th serves as a pivotal paleoceanographic proxy for delineating changes in the strength and geometry of ocean circulation as well as marine productivity throughout the last glacial-interglacial cycle. Its application builds on the fact that both Meridional Overturning Circulation (MOC) and scavenging by marine particles can shape the distribution of ²³¹Pa and ²³⁰Th in the ocean. Previous studies have addressed the crucial role of MOC on the ²³⁰Th and ²³¹Pa profiles and sedimentary ²³¹Pa/²³⁰Th in the Atlantic Ocean and Pacific Ocean, and the influence of boundary scavenging especially in the Pacific Ocean. However, how the MOC and scavenging processes exert their impact on sedimentary ²³¹Pa/²³⁰Th in the Indian Ocean remains unresolved. In this study, a two-dimensional model embedded with reversible scavenging and prescribed overturning schemes was employed to simulate the features of distribution of ²³⁰Th and ²³¹Pa within the water column and sediments in the Indian Ocean. In particular, the convex configuration deviating from the theoretical linear pattern for both ²³⁰Th and ²³¹Pa could be attributed to the deep convection, advection and upwelling of the deep water, highlighting the critical control of MOC. Concurrently, both bottom scavenging induced by re-suspended particles within the nepheloid layer and boundary scavenging facilitates the significant depletion of ²³¹Pa in depths in specific regions like the Madagascar Basin. The depth-profiles of sedimentary ²³¹Pa/²³⁰Th below ~1,500 m in the central basin can be identified as a result of MOC as the primary controlling factor, while boundary scavenging contributes to systematically lower the ²³¹Pa/²³⁰Th.