654 / 2024-09-18 20:25:11
On the distribution of 230Th and 231Pa in the Indian Ocean
Indian Ocean, 231Pa/230Th, Deep Ocean, Meridional Circulation, Scavenging
Session 10 - The biogeochemistry of trace metals in a changing ocean
Abstract Accepted
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. This finding reaffirms the efficacy of sedimentary 231Pa/230Th as a proxy for studying the alteration of deep ocean circulation in the Indian Ocean.